- All Implemented Interfaces:
Closeable
,AutoCloseable
,Iterator<String>
A Scanner
breaks its input into tokens using a
delimiter pattern, which by default matches whitespace. The resulting
tokens may then be converted into values of different types using the
various next
methods.
For example, this code allows a user to read a number from the console.
var con = System.console();
if (con != null) {
Scanner sc = new Scanner(con.reader()
);
int i = sc.nextInt();
}
As another example, this code allows long
types to be
assigned from entries in a file myNumbers
:
Scanner sc = new Scanner(new File("myNumbers"));
while (sc.hasNextLong()) {
long aLong = sc.nextLong();
}
The scanner can also use delimiters other than whitespace. This example reads several items in from a string:
String input = "1 fish 2 fish red fish blue fish";
Scanner s = new Scanner(input).useDelimiter("\\s*fish\\s*");
System.out.println(s.nextInt());
System.out.println(s.nextInt());
System.out.println(s.next());
System.out.println(s.next());
s.close();
prints the following output:
1 2 red blue
The same output can be generated with this code, which uses a regular expression to parse all four tokens at once:
String input = "1 fish 2 fish red fish blue fish";
Scanner s = new Scanner(input);
s.findInLine("(\\d+) fish (\\d+) fish (\\w+) fish (\\w+)");
MatchResult result = s.match();
for (int i=1; i<=result.groupCount(); i++)
System.out.println(result.group(i));
s.close();
The default whitespace delimiter used
by a scanner is as recognized by Character.isWhitespace()
. The reset()
method will reset the value of the scanner's delimiter to the default
whitespace delimiter regardless of whether it was previously changed.
A scanning operation may block waiting for input.
The next()
and hasNext()
methods and their
companion methods (such as nextInt()
and
hasNextInt()
) first skip any input that matches the delimiter
pattern, and then attempt to return the next token. Both hasNext()
and next()
methods may block waiting for further input. Whether a
hasNext()
method blocks has no connection to whether or not its
associated next()
method will block. The tokens()
method
may also block waiting for input.
The findInLine()
,
findWithinHorizon()
,
skip()
, and findAll()
methods operate independently of the delimiter pattern. These methods will
attempt to match the specified pattern with no regard to delimiters in the
input and thus can be used in special circumstances where delimiters are
not relevant. These methods may block waiting for more input.
When a scanner throws an InputMismatchException
, the scanner
will not pass the token that caused the exception, so that it may be
retrieved or skipped via some other method.
Depending upon the type of delimiting pattern, empty tokens may be
returned. For example, the pattern "\\s+"
will return no empty
tokens since it matches multiple instances of the delimiter. The delimiting
pattern "\\s"
could return empty tokens since it only passes one
space at a time.
A scanner can read text from any object which implements the Readable
interface. If an invocation of the underlying
readable's read()
method throws an IOException
then the scanner assumes that the end of the input
has been reached. The most recent IOException
thrown by the
underlying readable can be retrieved via the ioException()
method.
When a Scanner
is closed, it will close its input source
if the source implements the Closeable
interface.
A Scanner
is not safe for multithreaded use without
external synchronization.
Unless otherwise mentioned, passing a null
parameter into
any method of a Scanner
will cause a
NullPointerException
to be thrown.
A scanner will default to interpreting numbers as decimal unless a
different radix has been set by using the useRadix(int)
method. The
reset()
method will reset the value of the scanner's radix to
10
regardless of whether it was previously changed.
Localized numbers
An instance of this class is capable of scanning numbers in the standard
formats as well as in the formats of the scanner's locale. A scanner's
initial locale is the value returned by the Locale.getDefault(Locale.Category.FORMAT)
method; it may be changed via the useLocale()
method. The reset()
method will reset the value of the
scanner's locale to the initial locale regardless of whether it was
previously changed.
The localized formats are defined in terms of the following parameters,
which for a particular locale are taken from that locale's DecimalFormat
object, df
, and its and
DecimalFormatSymbols
object,
dfs
.
- LocalGroupSeparator
- The character used to separate thousands groups, i.e.,
dfs.
getGroupingSeparator()
- LocalDecimalSeparator
- The character used for the decimal point, i.e.,
dfs.
getDecimalSeparator()
- LocalPositivePrefix
- The string that appears before a positive number (may be empty), i.e.,
df.
getPositivePrefix()
- LocalPositiveSuffix
- The string that appears after a positive number (may be empty), i.e.,
df.
getPositiveSuffix()
- LocalNegativePrefix
- The string that appears before a negative number (may be empty), i.e.,
df.
getNegativePrefix()
- LocalNegativeSuffix
- The string that appears after a negative number (may be empty), i.e.,
df.
getNegativeSuffix()
- LocalNaN
- The string that represents not-a-number for floating-point values, i.e.,
dfs.
getNaN()
- LocalInfinity
- The string that represents infinity for floating-point values, i.e.,
dfs.
getInfinity()
Number syntax
The strings that can be parsed as numbers by an instance of this class are specified in terms of the following regular-expression grammar, where Rmax is the highest digit in the radix being used (for example, Rmax is 9 in base 10).
- NonAsciiDigit:
- A non-ASCII character c for which
Character.isDigit
(c)
returns true - Non0Digit:
[1-
Rmax] |
NonASCIIDigit- Digit:
[0-
Rmax] |
NonASCIIDigit- GroupedNumeral:
(
Non0Digit Digit?
Digit?
(
LocalGroupSeparator Digit Digit Digit)+ )
- Numeral:
( (
Digit+ ) |
GroupedNumeral)
- Integer:
( [-+]? (
Numeral) )
|
LocalPositivePrefix Numeral LocalPositiveSuffix|
LocalNegativePrefix Numeral LocalNegativeSuffix- DecimalNumeral:
- Numeral
|
Numeral LocalDecimalSeparator Digit*
|
LocalDecimalSeparator Digit+
- Exponent:
( [eE] [+-]?
Digit+ )
- Decimal:
( [-+]?
DecimalNumeral Exponent? )
|
LocalPositivePrefix DecimalNumeral LocalPositiveSuffix Exponent?
|
LocalNegativePrefix DecimalNumeral LocalNegativeSuffix Exponent?
- HexFloat:
[-+]? 0[xX][0-9a-fA-F]*\.[0-9a-fA-F]+ ([pP][-+]?[0-9]+)?
- NonNumber:
NaN |
LocalNan| Infinity |
LocalInfinity- SignedNonNumber:
( [-+]?
NonNumber)
|
LocalPositivePrefix NonNumber LocalPositiveSuffix|
LocalNegativePrefix NonNumber LocalNegativeSuffix- Float:
- Decimal
|
HexFloat|
SignedNonNumber
Whitespace is not significant in the above regular expressions.
- Since:
- 1.5
-
Constructor Summary
ConstructorDescriptionConstructs a newScanner
that produces values scanned from the specified file.Constructs a newScanner
that produces values scanned from the specified file.Constructs a newScanner
that produces values scanned from the specified file.Scanner
(InputStream source) Constructs a newScanner
that produces values scanned from the specified input stream.Scanner
(InputStream source, String charsetName) Constructs a newScanner
that produces values scanned from the specified input stream.Scanner
(InputStream source, Charset charset) Constructs a newScanner
that produces values scanned from the specified input stream.Constructs a newScanner
that produces values scanned from the specified source.Constructs a newScanner
that produces values scanned from the specified string.Scanner
(ReadableByteChannel source) Constructs a newScanner
that produces values scanned from the specified channel.Scanner
(ReadableByteChannel source, String charsetName) Constructs a newScanner
that produces values scanned from the specified channel.Scanner
(ReadableByteChannel source, Charset charset) Constructs a newScanner
that produces values scanned from the specified channel.Constructs a newScanner
that produces values scanned from the specified file.Constructs a newScanner
that produces values scanned from the specified file.Constructs a newScanner
that produces values scanned from the specified file. -
Method Summary
Modifier and TypeMethodDescriptionvoid
close()
Closes this scanner.Returns thePattern
thisScanner
is currently using to match delimiters.Returns a stream of match results that match the provided pattern string.Returns a stream of match results from this scanner.findInLine
(String pattern) Attempts to find the next occurrence of a pattern constructed from the specified string, ignoring delimiters.findInLine
(Pattern pattern) Attempts to find the next occurrence of the specified pattern ignoring delimiters.findWithinHorizon
(String pattern, int horizon) Attempts to find the next occurrence of a pattern constructed from the specified string, ignoring delimiters.findWithinHorizon
(Pattern pattern, int horizon) Attempts to find the next occurrence of the specified pattern.boolean
hasNext()
Returns true if this scanner has another token in its input.boolean
Returns true if the next token matches the pattern constructed from the specified string.boolean
Returns true if the next complete token matches the specified pattern.boolean
Returns true if the next token in this scanner's input can be interpreted as aBigDecimal
using thenextBigDecimal()
method.boolean
Returns true if the next token in this scanner's input can be interpreted as aBigInteger
in the default radix using thenextBigInteger()
method.boolean
hasNextBigInteger
(int radix) Returns true if the next token in this scanner's input can be interpreted as aBigInteger
in the specified radix using thenextBigInteger()
method.boolean
Returns true if the next token in this scanner's input can be interpreted as a boolean value using a case insensitive pattern created from the string "true|false".boolean
Returns true if the next token in this scanner's input can be interpreted as a byte value in the default radix using thenextByte()
method.boolean
hasNextByte
(int radix) Returns true if the next token in this scanner's input can be interpreted as a byte value in the specified radix using thenextByte()
method.boolean
Returns true if the next token in this scanner's input can be interpreted as a double value using thenextDouble()
method.boolean
Returns true if the next token in this scanner's input can be interpreted as a float value using thenextFloat()
method.boolean
Returns true if the next token in this scanner's input can be interpreted as an int value in the default radix using thenextInt()
method.boolean
hasNextInt
(int radix) Returns true if the next token in this scanner's input can be interpreted as an int value in the specified radix using thenextInt()
method.boolean
Returns true if there is another line in the input of this scanner.boolean
Returns true if the next token in this scanner's input can be interpreted as a long value in the default radix using thenextLong()
method.boolean
hasNextLong
(int radix) Returns true if the next token in this scanner's input can be interpreted as a long value in the specified radix using thenextLong()
method.boolean
Returns true if the next token in this scanner's input can be interpreted as a short value in the default radix using thenextShort()
method.boolean
hasNextShort
(int radix) Returns true if the next token in this scanner's input can be interpreted as a short value in the specified radix using thenextShort()
method.Returns theIOException
last thrown by thisScanner
's underlyingReadable
.locale()
Returns this scanner's locale.match()
Returns the match result of the last scanning operation performed by this scanner.next()
Finds and returns the next complete token from this scanner.Returns the next token if it matches the pattern constructed from the specified string.Returns the next token if it matches the specified pattern.Scans the next token of the input as aBigDecimal
.Scans the next token of the input as aBigInteger
.nextBigInteger
(int radix) Scans the next token of the input as aBigInteger
.boolean
Scans the next token of the input into a boolean value and returns that value.byte
nextByte()
Scans the next token of the input as abyte
.byte
nextByte
(int radix) Scans the next token of the input as abyte
.double
Scans the next token of the input as adouble
.float
Scans the next token of the input as afloat
.int
nextInt()
Scans the next token of the input as anint
.int
nextInt
(int radix) Scans the next token of the input as anint
.nextLine()
Advances this scanner past the current line and returns the input that was skipped.long
nextLong()
Scans the next token of the input as along
.long
nextLong
(int radix) Scans the next token of the input as along
.short
Scans the next token of the input as ashort
.short
nextShort
(int radix) Scans the next token of the input as ashort
.int
radix()
Returns this scanner's default radix.void
remove()
The remove operation is not supported by this implementation ofIterator
.reset()
Resets this scanner.Skips input that matches a pattern constructed from the specified string.Skips input that matches the specified pattern, ignoring delimiters.tokens()
Returns a stream of delimiter-separated tokens from this scanner.toString()
Returns the string representation of thisScanner
.useDelimiter
(String pattern) Sets this scanner's delimiting pattern to a pattern constructed from the specifiedString
.useDelimiter
(Pattern pattern) Sets this scanner's delimiting pattern to the specified pattern.Sets this scanner's locale to the specified locale.useRadix
(int radix) Sets this scanner's default radix to the specified radix.Methods declared in class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
Methods declared in interface java.util.Iterator
forEachRemaining
-
Constructor Details
-
Scanner
Constructs a newScanner
that produces values scanned from the specified source.- Parameters:
source
- A character source implementing theReadable
interface
-
Scanner
Constructs a newScanner
that produces values scanned from the specified input stream. Bytes from the stream are converted into characters using the default charset.- Parameters:
source
- An input stream to be scanned- See Also:
-
Scanner
Constructs a newScanner
that produces values scanned from the specified input stream. Bytes from the stream are converted into characters using the specified charset.- Parameters:
source
- An input stream to be scannedcharsetName
- The encoding type used to convert bytes from the stream into characters to be scanned- Throws:
IllegalArgumentException
- if the specified character set does not exist
-
Scanner
Constructs a newScanner
that produces values scanned from the specified input stream. Bytes from the stream are converted into characters using the specified charset.- Parameters:
source
- an input stream to be scannedcharset
- the charset used to convert bytes from the file into characters to be scanned- Since:
- 10
-
Scanner
Constructs a newScanner
that produces values scanned from the specified file. Bytes from the file are converted into characters using the default charset.- Parameters:
source
- A file to be scanned- Throws:
FileNotFoundException
- if source is not found- See Also:
-
Scanner
Constructs a newScanner
that produces values scanned from the specified file. Bytes from the file are converted into characters using the specified charset.- Parameters:
source
- A file to be scannedcharsetName
- The encoding type used to convert bytes from the file into characters to be scanned- Throws:
FileNotFoundException
- if source is not foundIllegalArgumentException
- if the specified encoding is not found
-
Scanner
Constructs a newScanner
that produces values scanned from the specified file. Bytes from the file are converted into characters using the specified charset.- Parameters:
source
- A file to be scannedcharset
- The charset used to convert bytes from the file into characters to be scanned- Throws:
IOException
- if an I/O error occurs opening the source- Since:
- 10
-
Scanner
Constructs a newScanner
that produces values scanned from the specified file. Bytes from the file are converted into characters using the default charset.- Parameters:
source
- the path to the file to be scanned- Throws:
IOException
- if an I/O error occurs opening source- Since:
- 1.7
- See Also:
-
Scanner
Constructs a newScanner
that produces values scanned from the specified file. Bytes from the file are converted into characters using the specified charset.- Parameters:
source
- the path to the file to be scannedcharsetName
- The encoding type used to convert bytes from the file into characters to be scanned- Throws:
IOException
- if an I/O error occurs opening sourceIllegalArgumentException
- if the specified encoding is not found- Since:
- 1.7
-
Scanner
Constructs a newScanner
that produces values scanned from the specified file. Bytes from the file are converted into characters using the specified charset.- Parameters:
source
- the path to the file to be scannedcharset
- the charset used to convert bytes from the file into characters to be scanned- Throws:
IOException
- if an I/O error occurs opening the source- Since:
- 10
-
Scanner
Constructs a newScanner
that produces values scanned from the specified string.- Parameters:
source
- A string to scan
-
Scanner
Constructs a newScanner
that produces values scanned from the specified channel. Bytes from the source are converted into characters using the default charset.- Parameters:
source
- A channel to scan- See Also:
-
Scanner
Constructs a newScanner
that produces values scanned from the specified channel. Bytes from the source are converted into characters using the specified charset.- Parameters:
source
- A channel to scancharsetName
- The encoding type used to convert bytes from the channel into characters to be scanned- Throws:
IllegalArgumentException
- if the specified character set does not exist
-
Scanner
Constructs a newScanner
that produces values scanned from the specified channel. Bytes from the source are converted into characters using the specified charset.- Parameters:
source
- a channel to scancharset
- the encoding type used to convert bytes from the channel into characters to be scanned- Since:
- 10
-
-
Method Details
-
close
public void close()Closes this scanner.If this scanner has not yet been closed then if its underlying readable also implements the
Closeable
interface then the readable'sclose
method will be invoked. If this scanner is already closed then invoking this method will have no effect.Attempting to perform search operations after a scanner has been closed will result in an
IllegalStateException
.- Specified by:
close
in interfaceAutoCloseable
- Specified by:
close
in interfaceCloseable
-
ioException
Returns theIOException
last thrown by thisScanner
's underlyingReadable
. This method returnsnull
if no such exception exists.- Returns:
- the last exception thrown by this scanner's readable
-
delimiter
Returns thePattern
thisScanner
is currently using to match delimiters.- Returns:
- this scanner's delimiting pattern.
-
useDelimiter
Sets this scanner's delimiting pattern to the specified pattern.- Parameters:
pattern
- A delimiting pattern- Returns:
- this scanner
-
useDelimiter
Sets this scanner's delimiting pattern to a pattern constructed from the specifiedString
.An invocation of this method of the form
useDelimiter(pattern)
behaves in exactly the same way as the invocationuseDelimiter(Pattern.compile(pattern))
.Invoking the
reset()
method will set the scanner's delimiter to the default.- Parameters:
pattern
- A string specifying a delimiting pattern- Returns:
- this scanner
-
locale
Returns this scanner's locale.A scanner's locale affects many elements of its default primitive matching regular expressions; see localized numbers above.
- Returns:
- this scanner's locale
-
useLocale
Sets this scanner's locale to the specified locale.A scanner's locale affects many elements of its default primitive matching regular expressions; see localized numbers above.
Invoking the
reset()
method will set the scanner's locale to the initial locale.- Parameters:
locale
- A string specifying the locale to use- Returns:
- this scanner
-
radix
public int radix()Returns this scanner's default radix.A scanner's radix affects elements of its default number matching regular expressions; see localized numbers above.
- Returns:
- the default radix of this scanner
-
useRadix
Sets this scanner's default radix to the specified radix.A scanner's radix affects elements of its default number matching regular expressions; see localized numbers above.
If the radix is less than
Character.MIN_RADIX
or greater thanCharacter.MAX_RADIX
, then anIllegalArgumentException
is thrown.Invoking the
reset()
method will set the scanner's radix to10
.- Parameters:
radix
- The radix to use when scanning numbers- Returns:
- this scanner
- Throws:
IllegalArgumentException
- if radix is out of range
-
match
Returns the match result of the last scanning operation performed by this scanner. This method throwsIllegalStateException
if no match has been performed, or if the last match was not successful.The various
next
methods ofScanner
make a match result available if they complete without throwing an exception. For instance, after an invocation of thenextInt()
method that returned an int, this method returns aMatchResult
for the search of the Integer regular expression defined above. Similarly thefindInLine()
,findWithinHorizon()
, andskip()
methods will make a match available if they succeed.- Returns:
- a match result for the last match operation
- Throws:
IllegalStateException
- If no match result is available
-
toString
Returns the string representation of this
Scanner
. The string representation of aScanner
contains information that may be useful for debugging. The exact format is unspecified. -
hasNext
public boolean hasNext()Returns true if this scanner has another token in its input. This method may block while waiting for input to scan. The scanner does not advance past any input.- Specified by:
hasNext
in interfaceIterator<String>
- Returns:
- true if and only if this scanner has another token
- Throws:
IllegalStateException
- if this scanner is closed- See Also:
-
next
Finds and returns the next complete token from this scanner. A complete token is preceded and followed by input that matches the delimiter pattern. This method may block while waiting for input to scan, even if a previous invocation ofhasNext()
returnedtrue
.- Specified by:
next
in interfaceIterator<String>
- Returns:
- the next token
- Throws:
NoSuchElementException
- if no more tokens are availableIllegalStateException
- if this scanner is closed- See Also:
-
remove
public void remove()The remove operation is not supported by this implementation ofIterator
.- Specified by:
remove
in interfaceIterator<String>
- Throws:
UnsupportedOperationException
- if this method is invoked.- See Also:
-
hasNext
Returns true if the next token matches the pattern constructed from the specified string. The scanner does not advance past any input.An invocation of this method of the form
hasNext(pattern)
behaves in exactly the same way as the invocationhasNext(Pattern.compile(pattern))
.- Parameters:
pattern
- a string specifying the pattern to scan- Returns:
- true if and only if this scanner has another token matching the specified pattern
- Throws:
IllegalStateException
- if this scanner is closed
-
next
Returns the next token if it matches the pattern constructed from the specified string. If the match is successful, the scanner advances past the input that matched the pattern.An invocation of this method of the form
next(pattern)
behaves in exactly the same way as the invocationnext(Pattern.compile(pattern))
.- Parameters:
pattern
- a string specifying the pattern to scan- Returns:
- the next token
- Throws:
NoSuchElementException
- if no such tokens are availableIllegalStateException
- if this scanner is closed
-
hasNext
Returns true if the next complete token matches the specified pattern. A complete token is prefixed and postfixed by input that matches the delimiter pattern. This method may block while waiting for input. The scanner does not advance past any input.- Parameters:
pattern
- the pattern to scan for- Returns:
- true if and only if this scanner has another token matching the specified pattern
- Throws:
IllegalStateException
- if this scanner is closed
-
next
Returns the next token if it matches the specified pattern. This method may block while waiting for input to scan, even if a previous invocation ofhasNext(Pattern)
returnedtrue
. If the match is successful, the scanner advances past the input that matched the pattern.- Parameters:
pattern
- the pattern to scan for- Returns:
- the next token
- Throws:
NoSuchElementException
- if no more tokens are availableIllegalStateException
- if this scanner is closed
-
hasNextLine
public boolean hasNextLine()Returns true if there is another line in the input of this scanner. This method may block while waiting for input. The scanner does not advance past any input.- Returns:
- true if there is a line separator in the remaining input or if the input has other remaining characters
- Throws:
IllegalStateException
- if this scanner is closed
-
nextLine
Advances this scanner past the current line and returns the input that was skipped. This method returns the rest of the current line, excluding any line separator at the end. The position is set to the beginning of the next line.Since this method continues to search through the input looking for a line separator, it may buffer all of the input searching for the line to skip if no line separators are present.
- Returns:
- the line that was skipped
- Throws:
NoSuchElementException
- if no line was foundIllegalStateException
- if this scanner is closed
-
findInLine
Attempts to find the next occurrence of a pattern constructed from the specified string, ignoring delimiters.An invocation of this method of the form
findInLine(pattern)
behaves in exactly the same way as the invocationfindInLine(Pattern.compile(pattern))
.- Parameters:
pattern
- a string specifying the pattern to search for- Returns:
- the text that matched the specified pattern
- Throws:
IllegalStateException
- if this scanner is closed
-
findInLine
Attempts to find the next occurrence of the specified pattern ignoring delimiters. If the pattern is found before the next line separator, the scanner advances past the input that matched and returns the string that matched the pattern. If no such pattern is detected in the input up to the next line separator, thennull
is returned and the scanner's position is unchanged. This method may block waiting for input that matches the pattern.Since this method continues to search through the input looking for the specified pattern, it may buffer all of the input searching for the desired token if no line separators are present.
- Parameters:
pattern
- the pattern to scan for- Returns:
- the text that matched the specified pattern
- Throws:
IllegalStateException
- if this scanner is closed
-
findWithinHorizon
Attempts to find the next occurrence of a pattern constructed from the specified string, ignoring delimiters.An invocation of this method of the form
findWithinHorizon(pattern)
behaves in exactly the same way as the invocationfindWithinHorizon(Pattern.compile(pattern), horizon)
.- Parameters:
pattern
- a string specifying the pattern to search forhorizon
- the search horizon- Returns:
- the text that matched the specified pattern
- Throws:
IllegalStateException
- if this scanner is closedIllegalArgumentException
- if horizon is negative
-
findWithinHorizon
Attempts to find the next occurrence of the specified pattern.This method searches through the input up to the specified search horizon, ignoring delimiters. If the pattern is found the scanner advances past the input that matched and returns the string that matched the pattern. If no such pattern is detected then the null is returned and the scanner's position remains unchanged. This method may block waiting for input that matches the pattern.
A scanner will never search more than
horizon
code points beyond its current position. Note that a match may be clipped by the horizon; that is, an arbitrary match result may have been different if the horizon had been larger. The scanner treats the horizon as a transparent, non-anchoring bound (seeMatcher.useTransparentBounds(boolean)
andMatcher.useAnchoringBounds(boolean)
).If horizon is
0
, then the horizon is ignored and this method continues to search through the input looking for the specified pattern without bound. In this case it may buffer all of the input searching for the pattern.If horizon is negative, then an IllegalArgumentException is thrown.
- Parameters:
pattern
- the pattern to scan forhorizon
- the search horizon- Returns:
- the text that matched the specified pattern
- Throws:
IllegalStateException
- if this scanner is closedIllegalArgumentException
- if horizon is negative
-
skip
Skips input that matches the specified pattern, ignoring delimiters. This method will skip input if an anchored match of the specified pattern succeeds.If a match to the specified pattern is not found at the current position, then no input is skipped and a
NoSuchElementException
is thrown.Since this method seeks to match the specified pattern starting at the scanner's current position, patterns that can match a lot of input (".*", for example) may cause the scanner to buffer a large amount of input.
Note that it is possible to skip something without risking a
NoSuchElementException
by using a pattern that can match nothing, e.g.,sc.skip("[ \t]*")
.- Parameters:
pattern
- a string specifying the pattern to skip over- Returns:
- this scanner
- Throws:
NoSuchElementException
- if the specified pattern is not foundIllegalStateException
- if this scanner is closed
-
skip
Skips input that matches a pattern constructed from the specified string.An invocation of this method of the form
skip(pattern)
behaves in exactly the same way as the invocationskip(Pattern.compile(pattern))
.- Parameters:
pattern
- a string specifying the pattern to skip over- Returns:
- this scanner
- Throws:
IllegalStateException
- if this scanner is closed
-
hasNextBoolean
public boolean hasNextBoolean()Returns true if the next token in this scanner's input can be interpreted as a boolean value using a case insensitive pattern created from the string "true|false". The scanner does not advance past the input that matched.- Returns:
- true if and only if this scanner's next token is a valid boolean value
- Throws:
IllegalStateException
- if this scanner is closed
-
nextBoolean
public boolean nextBoolean()Scans the next token of the input into a boolean value and returns that value. This method will throwInputMismatchException
if the next token cannot be translated into a valid boolean value. If the match is successful, the scanner advances past the input that matched.- Returns:
- the boolean scanned from the input
- Throws:
InputMismatchException
- if the next token is not a valid booleanNoSuchElementException
- if input is exhaustedIllegalStateException
- if this scanner is closed
-
hasNextByte
public boolean hasNextByte()Returns true if the next token in this scanner's input can be interpreted as a byte value in the default radix using thenextByte()
method. The scanner does not advance past any input.- Returns:
- true if and only if this scanner's next token is a valid byte value
- Throws:
IllegalStateException
- if this scanner is closed
-
hasNextByte
public boolean hasNextByte(int radix) Returns true if the next token in this scanner's input can be interpreted as a byte value in the specified radix using thenextByte()
method. The scanner does not advance past any input.If the radix is less than
Character.MIN_RADIX
or greater thanCharacter.MAX_RADIX
, then anIllegalArgumentException
is thrown.- Parameters:
radix
- the radix used to interpret the token as a byte value- Returns:
- true if and only if this scanner's next token is a valid byte value
- Throws:
IllegalStateException
- if this scanner is closedIllegalArgumentException
- if the radix is out of range
-
nextByte
public byte nextByte()Scans the next token of the input as abyte
.An invocation of this method of the form
nextByte()
behaves in exactly the same way as the invocationnextByte(radix)
, whereradix
is the default radix of this scanner.- Returns:
- the
byte
scanned from the input - Throws:
InputMismatchException
- if the next token does not match the Integer regular expression, or is out of rangeNoSuchElementException
- if input is exhaustedIllegalStateException
- if this scanner is closed
-
nextByte
public byte nextByte(int radix) Scans the next token of the input as abyte
. This method will throwInputMismatchException
if the next token cannot be translated into a valid byte value as described below. If the translation is successful, the scanner advances past the input that matched.If the next token matches the Integer regular expression defined above then the token is converted into a
byte
value as if by removing all locale specific prefixes, group separators, and locale specific suffixes, then mapping non-ASCII digits into ASCII digits viaCharacter.digit
, prepending a negative sign (-) if the locale specific negative prefixes and suffixes were present, and passing the resulting string toByte.parseByte
with the specified radix.If the radix is less than
Character.MIN_RADIX
or greater thanCharacter.MAX_RADIX
, then anIllegalArgumentException
is thrown.- Parameters:
radix
- the radix used to interpret the token as a byte value- Returns:
- the
byte
scanned from the input - Throws:
InputMismatchException
- if the next token does not match the Integer regular expression, or is out of rangeNoSuchElementException
- if input is exhaustedIllegalStateException
- if this scanner is closedIllegalArgumentException
- if the radix is out of range
-
hasNextShort
public boolean hasNextShort()Returns true if the next token in this scanner's input can be interpreted as a short value in the default radix using thenextShort()
method. The scanner does not advance past any input.- Returns:
- true if and only if this scanner's next token is a valid short value in the default radix
- Throws:
IllegalStateException
- if this scanner is closed
-
hasNextShort
public boolean hasNextShort(int radix) Returns true if the next token in this scanner's input can be interpreted as a short value in the specified radix using thenextShort()
method. The scanner does not advance past any input.If the radix is less than
Character.MIN_RADIX
or greater thanCharacter.MAX_RADIX
, then anIllegalArgumentException
is thrown.- Parameters:
radix
- the radix used to interpret the token as a short value- Returns:
- true if and only if this scanner's next token is a valid short value in the specified radix
- Throws:
IllegalStateException
- if this scanner is closedIllegalArgumentException
- if the radix is out of range
-
nextShort
public short nextShort()Scans the next token of the input as ashort
.An invocation of this method of the form
nextShort()
behaves in exactly the same way as the invocationnextShort(radix)
, whereradix
is the default radix of this scanner.- Returns:
- the
short
scanned from the input - Throws:
InputMismatchException
- if the next token does not match the Integer regular expression, or is out of rangeNoSuchElementException
- if input is exhaustedIllegalStateException
- if this scanner is closed
-
nextShort
public short nextShort(int radix) Scans the next token of the input as ashort
. This method will throwInputMismatchException
if the next token cannot be translated into a valid short value as described below. If the translation is successful, the scanner advances past the input that matched.If the next token matches the Integer regular expression defined above then the token is converted into a
short
value as if by removing all locale specific prefixes, group separators, and locale specific suffixes, then mapping non-ASCII digits into ASCII digits viaCharacter.digit
, prepending a negative sign (-) if the locale specific negative prefixes and suffixes were present, and passing the resulting string toShort.parseShort
with the specified radix.If the radix is less than
Character.MIN_RADIX
or greater thanCharacter.MAX_RADIX
, then anIllegalArgumentException
is thrown.- Parameters:
radix
- the radix used to interpret the token as a short value- Returns:
- the
short
scanned from the input - Throws:
InputMismatchException
- if the next token does not match the Integer regular expression, or is out of rangeNoSuchElementException
- if input is exhaustedIllegalStateException
- if this scanner is closedIllegalArgumentException
- if the radix is out of range
-
hasNextInt
public boolean hasNextInt()Returns true if the next token in this scanner's input can be interpreted as an int value in the default radix using thenextInt()
method. The scanner does not advance past any input.- Returns:
- true if and only if this scanner's next token is a valid int value
- Throws:
IllegalStateException
- if this scanner is closed
-
hasNextInt
public boolean hasNextInt(int radix) Returns true if the next token in this scanner's input can be interpreted as an int value in the specified radix using thenextInt()
method. The scanner does not advance past any input.If the radix is less than
Character.MIN_RADIX
or greater thanCharacter.MAX_RADIX
, then anIllegalArgumentException
is thrown.- Parameters:
radix
- the radix used to interpret the token as an int value- Returns:
- true if and only if this scanner's next token is a valid int value
- Throws:
IllegalStateException
- if this scanner is closedIllegalArgumentException
- if the radix is out of range
-
nextInt
public int nextInt()Scans the next token of the input as anint
.An invocation of this method of the form
nextInt()
behaves in exactly the same way as the invocationnextInt(radix)
, whereradix
is the default radix of this scanner.- Returns:
- the
int
scanned from the input - Throws:
InputMismatchException
- if the next token does not match the Integer regular expression, or is out of rangeNoSuchElementException
- if input is exhaustedIllegalStateException
- if this scanner is closed
-
nextInt
public int nextInt(int radix) Scans the next token of the input as anint
. This method will throwInputMismatchException
if the next token cannot be translated into a valid int value as described below. If the translation is successful, the scanner advances past the input that matched.If the next token matches the Integer regular expression defined above then the token is converted into an
int
value as if by removing all locale specific prefixes, group separators, and locale specific suffixes, then mapping non-ASCII digits into ASCII digits viaCharacter.digit
, prepending a negative sign (-) if the locale specific negative prefixes and suffixes were present, and passing the resulting string toInteger.parseInt
with the specified radix.If the radix is less than
Character.MIN_RADIX
or greater thanCharacter.MAX_RADIX
, then anIllegalArgumentException
is thrown.- Parameters:
radix
- the radix used to interpret the token as an int value- Returns:
- the
int
scanned from the input - Throws:
InputMismatchException
- if the next token does not match the Integer regular expression, or is out of rangeNoSuchElementException
- if input is exhaustedIllegalStateException
- if this scanner is closedIllegalArgumentException
- if the radix is out of range
-
hasNextLong
public boolean hasNextLong()Returns true if the next token in this scanner's input can be interpreted as a long value in the default radix using thenextLong()
method. The scanner does not advance past any input.- Returns:
- true if and only if this scanner's next token is a valid long value
- Throws:
IllegalStateException
- if this scanner is closed
-
hasNextLong
public boolean hasNextLong(int radix) Returns true if the next token in this scanner's input can be interpreted as a long value in the specified radix using thenextLong()
method. The scanner does not advance past any input.If the radix is less than
Character.MIN_RADIX
or greater thanCharacter.MAX_RADIX
, then anIllegalArgumentException
is thrown.- Parameters:
radix
- the radix used to interpret the token as a long value- Returns:
- true if and only if this scanner's next token is a valid long value
- Throws:
IllegalStateException
- if this scanner is closedIllegalArgumentException
- if the radix is out of range
-
nextLong
public long nextLong()Scans the next token of the input as along
.An invocation of this method of the form
nextLong()
behaves in exactly the same way as the invocationnextLong(radix)
, whereradix
is the default radix of this scanner.- Returns:
- the
long
scanned from the input - Throws:
InputMismatchException
- if the next token does not match the Integer regular expression, or is out of rangeNoSuchElementException
- if input is exhaustedIllegalStateException
- if this scanner is closed
-
nextLong
public long nextLong(int radix) Scans the next token of the input as along
. This method will throwInputMismatchException
if the next token cannot be translated into a valid long value as described below. If the translation is successful, the scanner advances past the input that matched.If the next token matches the Integer regular expression defined above then the token is converted into a
long
value as if by removing all locale specific prefixes, group separators, and locale specific suffixes, then mapping non-ASCII digits into ASCII digits viaCharacter.digit
, prepending a negative sign (-) if the locale specific negative prefixes and suffixes were present, and passing the resulting string toLong.parseLong
with the specified radix.If the radix is less than
Character.MIN_RADIX
or greater thanCharacter.MAX_RADIX
, then anIllegalArgumentException
is thrown.- Parameters:
radix
- the radix used to interpret the token as an int value- Returns:
- the
long
scanned from the input - Throws:
InputMismatchException
- if the next token does not match the Integer regular expression, or is out of rangeNoSuchElementException
- if input is exhaustedIllegalStateException
- if this scanner is closedIllegalArgumentException
- if the radix is out of range
-
hasNextFloat
public boolean hasNextFloat()Returns true if the next token in this scanner's input can be interpreted as a float value using thenextFloat()
method. The scanner does not advance past any input.- Returns:
- true if and only if this scanner's next token is a valid float value
- Throws:
IllegalStateException
- if this scanner is closed
-
nextFloat
public float nextFloat()Scans the next token of the input as afloat
. This method will throwInputMismatchException
if the next token cannot be translated into a valid float value as described below. If the translation is successful, the scanner advances past the input that matched.If the next token matches the Float regular expression defined above then the token is converted into a
float
value as if by removing all locale specific prefixes, group separators, and locale specific suffixes, then mapping non-ASCII digits into ASCII digits viaCharacter.digit
, prepending a negative sign (-) if the locale specific negative prefixes and suffixes were present, and passing the resulting string toFloat.parseFloat
. If the token matches the localized NaN or infinity strings, then either "Nan" or "Infinity" is passed toFloat.parseFloat
as appropriate.- Returns:
- the
float
scanned from the input - Throws:
InputMismatchException
- if the next token does not match the Float regular expression, or is out of rangeNoSuchElementException
- if input is exhaustedIllegalStateException
- if this scanner is closed
-
hasNextDouble
public boolean hasNextDouble()Returns true if the next token in this scanner's input can be interpreted as a double value using thenextDouble()
method. The scanner does not advance past any input.- Returns:
- true if and only if this scanner's next token is a valid double value
- Throws:
IllegalStateException
- if this scanner is closed
-
nextDouble
public double nextDouble()Scans the next token of the input as adouble
. This method will throwInputMismatchException
if the next token cannot be translated into a valid double value. If the translation is successful, the scanner advances past the input that matched.If the next token matches the Float regular expression defined above then the token is converted into a
double
value as if by removing all locale specific prefixes, group separators, and locale specific suffixes, then mapping non-ASCII digits into ASCII digits viaCharacter.digit
, prepending a negative sign (-) if the locale specific negative prefixes and suffixes were present, and passing the resulting string toDouble.parseDouble
. If the token matches the localized NaN or infinity strings, then either "Nan" or "Infinity" is passed toDouble.parseDouble
as appropriate.- Returns:
- the
double
scanned from the input - Throws:
InputMismatchException
- if the next token does not match the Float regular expression, or is out of rangeNoSuchElementException
- if the input is exhaustedIllegalStateException
- if this scanner is closed
-
hasNextBigInteger
public boolean hasNextBigInteger()Returns true if the next token in this scanner's input can be interpreted as aBigInteger
in the default radix using thenextBigInteger()
method. The scanner does not advance past any input.- Returns:
- true if and only if this scanner's next token is a valid
BigInteger
- Throws:
IllegalStateException
- if this scanner is closed
-
hasNextBigInteger
public boolean hasNextBigInteger(int radix) Returns true if the next token in this scanner's input can be interpreted as aBigInteger
in the specified radix using thenextBigInteger()
method. The scanner does not advance past any input.If the radix is less than
Character.MIN_RADIX
or greater thanCharacter.MAX_RADIX
, then anIllegalArgumentException
is thrown.- Parameters:
radix
- the radix used to interpret the token as an integer- Returns:
- true if and only if this scanner's next token is a valid
BigInteger
- Throws:
IllegalStateException
- if this scanner is closedIllegalArgumentException
- if the radix is out of range
-
nextBigInteger
Scans the next token of the input as aBigInteger
.An invocation of this method of the form
nextBigInteger()
behaves in exactly the same way as the invocationnextBigInteger(radix)
, whereradix
is the default radix of this scanner.- Returns:
- the
BigInteger
scanned from the input - Throws:
InputMismatchException
- if the next token does not match the Integer regular expression, or is out of rangeNoSuchElementException
- if the input is exhaustedIllegalStateException
- if this scanner is closed
-
nextBigInteger
Scans the next token of the input as aBigInteger
.If the next token matches the Integer regular expression defined above then the token is converted into a
BigInteger
value as if by removing all group separators, mapping non-ASCII digits into ASCII digits via theCharacter.digit
, and passing the resulting string to theBigInteger(String, int)
constructor with the specified radix.If the radix is less than
Character.MIN_RADIX
or greater thanCharacter.MAX_RADIX
, then anIllegalArgumentException
is thrown.- Parameters:
radix
- the radix used to interpret the token- Returns:
- the
BigInteger
scanned from the input - Throws:
InputMismatchException
- if the next token does not match the Integer regular expression, or is out of rangeNoSuchElementException
- if the input is exhaustedIllegalStateException
- if this scanner is closedIllegalArgumentException
- if the radix is out of range
-
hasNextBigDecimal
public boolean hasNextBigDecimal()Returns true if the next token in this scanner's input can be interpreted as aBigDecimal
using thenextBigDecimal()
method. The scanner does not advance past any input.- Returns:
- true if and only if this scanner's next token is a valid
BigDecimal
- Throws:
IllegalStateException
- if this scanner is closed
-
nextBigDecimal
Scans the next token of the input as aBigDecimal
.If the next token matches the Decimal regular expression defined above then the token is converted into a
BigDecimal
value as if by removing all group separators, mapping non-ASCII digits into ASCII digits via theCharacter.digit
, and passing the resulting string to theBigDecimal(String)
constructor.- Returns:
- the
BigDecimal
scanned from the input - Throws:
InputMismatchException
- if the next token does not match the Decimal regular expression, or is out of rangeNoSuchElementException
- if the input is exhaustedIllegalStateException
- if this scanner is closed
-
reset
Resets this scanner.Resetting a scanner discards all of its explicit state information which may have been changed by invocations of
useDelimiter()
,useLocale()
, oruseRadix()
.An invocation of this method of the form
scanner.reset()
behaves in exactly the same way as the invocationscanner.useDelimiter("\\p{javaWhitespace}+") .useLocale(Locale.getDefault(Locale.Category.FORMAT)) .useRadix(10);
- Returns:
- this scanner
- Since:
- 1.6
-
tokens
Returns a stream of delimiter-separated tokens from this scanner. The stream contains the same tokens that would be returned, starting from this scanner's current state, by calling thenext()
method repeatedly until thehasNext()
method returns false.The resulting stream is sequential and ordered. All stream elements are non-null.
Scanning starts upon initiation of the terminal stream operation, using the current state of this scanner. Subsequent calls to any methods on this scanner other than
close()
andioException()
may return undefined results or may cause undefined effects on the returned stream. The returned stream's sourceSpliterator
is fail-fast and will, on a best-effort basis, throw aConcurrentModificationException
if any such calls are detected during stream pipeline execution.After stream pipeline execution completes, this scanner is left in an indeterminate state and cannot be reused.
If this scanner contains a resource that must be released, this scanner should be closed, either by calling its
close()
method, or by closing the returned stream. Closing the stream will close the underlying scanner.IllegalStateException
is thrown if the scanner has been closed when this method is called, or if this scanner is closed during stream pipeline execution.This method might block waiting for more input.
- API Note:
- For example, the following code will create a list of
comma-delimited tokens from a string:
List<String> result = new Scanner("abc,def,,ghi") .useDelimiter(",") .tokens() .collect(Collectors.toList());
The resulting list would contain
"abc"
,"def"
, the empty string, and"ghi"
. - Returns:
- a sequential stream of token strings
- Throws:
IllegalStateException
- if this scanner is closed- Since:
- 9
-
findAll
Returns a stream of match results from this scanner. The stream contains the same results in the same order that would be returned by callingfindWithinHorizon(pattern, 0)
and thenmatch()
successively as long asfindWithinHorizon()
finds matches.The resulting stream is sequential and ordered. All stream elements are non-null.
Scanning starts upon initiation of the terminal stream operation, using the current state of this scanner. Subsequent calls to any methods on this scanner other than
close()
andioException()
may return undefined results or may cause undefined effects on the returned stream. The returned stream's sourceSpliterator
is fail-fast and will, on a best-effort basis, throw aConcurrentModificationException
if any such calls are detected during stream pipeline execution.After stream pipeline execution completes, this scanner is left in an indeterminate state and cannot be reused.
If this scanner contains a resource that must be released, this scanner should be closed, either by calling its
close()
method, or by closing the returned stream. Closing the stream will close the underlying scanner.IllegalStateException
is thrown if the scanner has been closed when this method is called, or if this scanner is closed during stream pipeline execution.As with the
findWithinHorizon()
methods, this method might block waiting for additional input, and it might buffer an unbounded amount of input searching for a match.- API Note:
- For example, the following code will read a file and return a list
of all sequences of characters consisting of seven or more Latin capital
letters:
try (Scanner sc = new Scanner(Path.of("input.txt"))) { Pattern pat = Pattern.compile("[A-Z]{7,}"); List<String> capWords = sc.findAll(pat) .map(MatchResult::group) .collect(Collectors.toList()); }
- Parameters:
pattern
- the pattern to be matched- Returns:
- a sequential stream of match results
- Throws:
NullPointerException
- if pattern is nullIllegalStateException
- if this scanner is closed- Since:
- 9
-
findAll
Returns a stream of match results that match the provided pattern string. The effect is equivalent to the following code:scanner.findAll(Pattern.compile(patString))
- Parameters:
patString
- the pattern string- Returns:
- a sequential stream of match results
- Throws:
NullPointerException
- if patString is nullIllegalStateException
- if this scanner is closedPatternSyntaxException
- if the regular expression's syntax is invalid- Since:
- 9
- See Also:
-