Scanner

AI-generated Key Takeaways

• The Scanner class in Java parses text input from various sources like files, input streams, and strings, breaking it into tokens for processing.

• It provides methods to read different data types (e.g., nextInt(), nextDouble(), next()) and handles potential exceptions during parsing.

• Developers can customize delimiters and locales for flexible input handling, utilizing regular expressions for pattern matching.

• The class offers functionalities to check for tokens (hasNext...()), read them (next...()), find patterns, and control the overall scanner behavior.

• Although versatile and feature-rich, Scanner is not thread-safe and throws exceptions for invalid inputs or operations.

public final class Scanner extends Object
implements Iterator<String> Closeable

A simple text scanner which can parse primitive types and strings using regular expressions.

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 System.in:

Scanner sc = new Scanner(System.in);
     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 primitive-type 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 findInLine(String), findWithinHorizon(String, int), and skip(String) 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 Readable.read(CharBuffer) 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(Locale) 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.

Public Constructor Summary

	Scanner(Readable source) Constructs a new Scanner that produces values scanned from the specified source.
	Scanner(InputStream source) Constructs a new Scanner that produces values scanned from the specified input stream.
	Scanner(InputStream source, String charsetName) Constructs a new Scanner that produces values scanned from the specified input stream.
	Scanner(File source) Constructs a new Scanner that produces values scanned from the specified file.
	Scanner(File source, String charsetName) Constructs a new Scanner that produces values scanned from the specified file.
	Scanner(String source) Constructs a new Scanner that produces values scanned from the specified string.
	Scanner(ReadableByteChannel source) Constructs a new Scanner that produces values scanned from the specified channel.
	Scanner(ReadableByteChannel source, String charsetName) Constructs a new Scanner that produces values scanned from the specified channel.

Public Method Summary

void	close() Closes this scanner.
Pattern	delimiter() Returns the Pattern this Scanner is currently using to match delimiters.
String	findInLine(String pattern) Attempts to find the next occurrence of a pattern constructed from the specified string, ignoring delimiters.
String	findInLine(Pattern pattern) Attempts to find the next occurrence of the specified pattern ignoring delimiters.
String	findWithinHorizon(Pattern pattern, int horizon) Attempts to find the next occurrence of the specified pattern.
String	findWithinHorizon(String pattern, int horizon) Attempts to find the next occurrence of a pattern constructed from the specified string, ignoring delimiters.
boolean	hasNext() Returns true if this scanner has another token in its input.
boolean	hasNext(String pattern) Returns true if the next token matches the pattern constructed from the specified string.
boolean	hasNext(Pattern pattern) Returns true if the next complete token matches the specified pattern.
boolean	hasNextBigDecimal() Returns true if the next token in this scanner's input can be interpreted as a BigDecimal using the nextBigDecimal() method.
boolean	hasNextBigInteger(int radix) Returns true if the next token in this scanner's input can be interpreted as a BigInteger in the specified radix using the nextBigInteger() method.
boolean	hasNextBigInteger() Returns true if the next token in this scanner's input can be interpreted as a BigInteger in the default radix using the nextBigInteger() method.
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".
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 the nextByte() 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 the nextByte() method.
boolean	hasNextDouble() Returns true if the next token in this scanner's input can be interpreted as a double value using the nextDouble() method.
boolean	hasNextFloat() Returns true if the next token in this scanner's input can be interpreted as a float value using the nextFloat() method.
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 the nextInt() 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 the nextInt() method.
boolean	hasNextLine() Returns true if there is another line in the input of this scanner.
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 the nextLong() 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 the nextLong() method.
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 the nextShort() 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 the nextShort() method.
IOException	ioException() Returns the IOException last thrown by this Scanner's underlying Readable.
Locale	locale() Returns this scanner's locale.
MatchResult	match() Returns the match result of the last scanning operation performed by this scanner.
String	next(Pattern pattern) Returns the next token if it matches the specified pattern.
String	next() Finds and returns the next complete token from this scanner.
String	next(String pattern) Returns the next token if it matches the pattern constructed from the specified string.
BigDecimal	nextBigDecimal() Scans the next token of the input as a BigDecimal.
BigInteger	nextBigInteger() Scans the next token of the input as a BigInteger.
BigInteger	nextBigInteger(int radix) Scans the next token of the input as a BigInteger.
boolean	nextBoolean() Scans the next token of the input into a boolean value and returns that value.
byte	nextByte(int radix) Scans the next token of the input as a byte.
byte	nextByte() Scans the next token of the input as a byte.
double	nextDouble() Scans the next token of the input as a double.
float	nextFloat() Scans the next token of the input as a float.
int	nextInt() Scans the next token of the input as an int.
int	nextInt(int radix) Scans the next token of the input as an int.
String	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 a long.
long	nextLong(int radix) Scans the next token of the input as a long.
short	nextShort(int radix) Scans the next token of the input as a short.
short	nextShort() Scans the next token of the input as a short.
int	radix() Returns this scanner's default radix.
void	remove() The remove operation is not supported by this implementation of Iterator.
Scanner	reset() Resets this scanner.
Scanner	skip(String pattern) Skips input that matches a pattern constructed from the specified string.
Scanner	skip(Pattern pattern) Skips input that matches the specified pattern, ignoring delimiters.
String	toString() Returns the string representation of this Scanner.
Scanner	useDelimiter(Pattern pattern) Sets this scanner's delimiting pattern to the specified pattern.
Scanner	useDelimiter(String pattern) Sets this scanner's delimiting pattern to a pattern constructed from the specified String.
Scanner	useLocale(Locale locale) Sets this scanner's locale to the specified locale.
Scanner	useRadix(int radix) Sets this scanner's default radix to the specified radix.

Inherited Method Summary

From class java.lang.Object

Object	clone() Creates and returns a copy of this Object.
boolean	equals(Object obj) Compares this instance with the specified object and indicates if they are equal.
void	finalize() Invoked when the garbage collector has detected that this instance is no longer reachable.
final Class<?>	getClass() Returns the unique instance of Class that represents this object's class.
int	hashCode() Returns an integer hash code for this object.
final void	notify() Causes a thread which is waiting on this object's monitor (by means of calling one of the wait() methods) to be woken up.
final void	notifyAll() Causes all threads which are waiting on this object's monitor (by means of calling one of the wait() methods) to be woken up.
String	toString() Returns a string containing a concise, human-readable description of this object.
final void	wait(long timeout, int nanos) Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object or until the specified timeout expires.
final void	wait(long timeout) Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object or until the specified timeout expires.
final void	wait() Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object.

From interface java.util.Iterator

void	forEachRemaining(Consumer<? super E> action) Performs the given action for each remaining element until all elements have been processed or the action throws an exception.
abstract boolean	hasNext() Returns true if the iteration has more elements.
abstract String	next() Returns the next element in the iteration.
void	remove() Removes from the underlying collection the last element returned by this iterator (optional operation).

From interface java.io.Closeable

abstract void

close() Closes this stream and releases any system resources associated with it.

From interface java.lang.AutoCloseable

abstract void

close() Closes this resource, relinquishing any underlying resources.

Public Constructors

public Scanner (Readable source)

Constructs a new Scanner that produces values scanned from the specified source.

Parameters

source	A character source implementing the Readable interface

public Scanner (InputStream source)

Constructs a new Scanner that produces values scanned from the specified input stream. Bytes from the stream are converted into characters using the underlying platform's {@linkplain java.nio.charset.Charset#defaultCharset() default charset}.

Parameters

source	An input stream to be scanned

public Scanner (InputStream source, String charsetName)

Constructs a new Scanner 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 scanned
charsetName	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

public Scanner (File source)

Constructs a new Scanner that produces values scanned from the specified file. Bytes from the file are converted into characters using the underlying platform's {@linkplain java.nio.charset.Charset#defaultCharset() default charset}.

Parameters

source	A file to be scanned

Throws

FileNotFoundException	if source is not found

public Scanner (File source, String charsetName)

Constructs a new Scanner 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 scanned
charsetName	The encoding type used to convert bytes from the file into characters to be scanned

Throws

FileNotFoundException	if source is not found
IllegalArgumentException	if the specified encoding is not found

public Scanner (String source)

Constructs a new Scanner that produces values scanned from the specified string.

Parameters

source	A string to scan

public Scanner (ReadableByteChannel source)

Constructs a new Scanner that produces values scanned from the specified channel. Bytes from the source are converted into characters using the underlying platform's {@linkplain java.nio.charset.Charset#defaultCharset() default charset}.

Parameters

source	A channel to scan

public Scanner (ReadableByteChannel source, String charsetName)

Constructs a new Scanner 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 scan
charsetName	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

Public Methods

public void close ()

Closes this scanner.

If this scanner has not yet been closed then if its underlying {@linkplain java.lang.Readable readable} also implements the Closeable interface then the readable's close 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.

public Pattern delimiter ()

Returns the Pattern this Scanner is currently using to match delimiters.

Returns

• this scanner's delimiting pattern.

public String findInLine (String pattern)

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 invocation findInLine(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

public String findInLine (Pattern pattern)

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, then null 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

public String findWithinHorizon (Pattern pattern, int horizon)

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 (see Matcher.useTransparentBounds(boolean) and Matcher.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 for
horizon	the search horizon

Returns

• the text that matched the specified pattern

Throws

IllegalStateException	if this scanner is closed
IllegalArgumentException	if horizon is negative

public String findWithinHorizon (String pattern, int horizon)

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 invocation findWithinHorizon(Pattern.compile(pattern, horizon)).

Parameters

pattern	a string specifying the pattern to search for
horizon	the search horizon

Returns

• the text that matched the specified pattern

Throws

IllegalStateException	if this scanner is closed
IllegalArgumentException	if horizon is negative

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.

Returns

• true if and only if this scanner has another token

Throws

IllegalStateException	if this scanner is closed

See Also

• Iterator

public boolean hasNext (String pattern)

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 invocation hasNext(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

public boolean hasNext (Pattern pattern)

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

public boolean hasNextBigDecimal ()

Returns true if the next token in this scanner's input can be interpreted as a BigDecimal using the nextBigDecimal() 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

public boolean hasNextBigInteger (int radix)

Returns true if the next token in this scanner's input can be interpreted as a BigInteger in the specified radix using the nextBigInteger() method. The scanner does not advance past any input.

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 closed

public boolean hasNextBigInteger ()

Returns true if the next token in this scanner's input can be interpreted as a BigInteger in the default radix using the nextBigInteger() 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

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

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 the nextByte() 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

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 the nextByte() method. The scanner does not advance past any input.

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 closed

public boolean hasNextDouble ()

Returns true if the next token in this scanner's input can be interpreted as a double value using the nextDouble() 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

public boolean hasNextFloat ()

Returns true if the next token in this scanner's input can be interpreted as a float value using the nextFloat() 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

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 the nextInt() 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

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 the nextInt() method. The scanner does not advance past any input.

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 closed

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 and only if this scanner has another line of input

Throws

IllegalStateException	if this scanner is closed

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 the nextLong() 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

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 the nextLong() method. The scanner does not advance past any input.

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 closed

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 the nextShort() 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

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 the nextShort() method. The scanner does not advance past any input.

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 closed

public IOException ioException ()

Returns the IOException last thrown by this Scanner's underlying Readable. This method returns null if no such exception exists.

Returns

• the last exception thrown by this scanner's readable

public Locale 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

public MatchResult match ()

Returns the match result of the last scanning operation performed by this scanner. This method throws IllegalStateException if no match has been performed, or if the last match was not successful.

The various nextmethods of Scanner make a match result available if they complete without throwing an exception. For instance, after an invocation of the nextInt() method that returned an int, this method returns a MatchResult for the search of the Integer regular expression defined above. Similarly the findInLine(String), findWithinHorizon(String, int), and skip(String) 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

public String next (Pattern pattern)

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 of hasNext(Pattern) returned true. 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 available
IllegalStateException	if this scanner is closed

public String 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 of hasNext() returned true.

Returns

• the next token

Throws

NoSuchElementException	if no more tokens are available
IllegalStateException	if this scanner is closed

See Also

• Iterator

public String next (String pattern)

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 invocation next(Pattern.compile(pattern)).

Parameters

pattern	a string specifying the pattern to scan

Returns

• the next token

Throws

NoSuchElementException	if no such tokens are available
IllegalStateException	if this scanner is closed

public BigDecimal nextBigDecimal ()

Scans the next token of the input as a BigDecimal.

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 the Character.digit, and passing the resulting string to the BigDecimal(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 range
NoSuchElementException	if the input is exhausted
IllegalStateException	if this scanner is closed

public BigInteger nextBigInteger ()

Scans the next token of the input as a BigInteger.

An invocation of this method of the form nextBigInteger() behaves in exactly the same way as the invocation nextBigInteger(radix), where radix 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 range
NoSuchElementException	if the input is exhausted
IllegalStateException	if this scanner is closed

public BigInteger nextBigInteger (int radix)

Scans the next token of the input as a BigInteger.

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 the Character.digit, and passing the resulting string to the BigInteger(String, int) constructor with the specified radix.

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 range
NoSuchElementException	if the input is exhausted
IllegalStateException	if this scanner is closed

public boolean nextBoolean ()

Scans the next token of the input into a boolean value and returns that value. This method will throw InputMismatchException 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 boolean
NoSuchElementException	if input is exhausted
IllegalStateException	if this scanner is closed

public byte nextByte (int radix)

Scans the next token of the input as a byte. This method will throw InputMismatchException 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 via Character.digit, prepending a negative sign (-) if the locale specific negative prefixes and suffixes were present, and passing the resulting string to Byte.parseByte with the specified radix.

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 range
NoSuchElementException	if input is exhausted
IllegalStateException	if this scanner is closed

public byte nextByte ()

Scans the next token of the input as a byte.

An invocation of this method of the form nextByte() behaves in exactly the same way as the invocation nextByte(radix), where radix 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 range
NoSuchElementException	if input is exhausted
IllegalStateException	if this scanner is closed

public double nextDouble ()

Scans the next token of the input as a double. This method will throw InputMismatchException 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 via Character.digit, prepending a negative sign (-) if the locale specific negative prefixes and suffixes were present, and passing the resulting string to Double.parseDouble. If the token matches the localized NaN or infinity strings, then either "Nan" or "Infinity" is passed to Double.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 range
NoSuchElementException	if the input is exhausted
IllegalStateException	if this scanner is closed

public float nextFloat ()

Scans the next token of the input as a float. This method will throw InputMismatchException 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 via Character.digit, prepending a negative sign (-) if the locale specific negative prefixes and suffixes were present, and passing the resulting string to Float.parseFloat. If the token matches the localized NaN or infinity strings, then either "Nan" or "Infinity" is passed to Float.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 range
NoSuchElementException	if input is exhausted
IllegalStateException	if this scanner is closed

public int nextInt ()

Scans the next token of the input as an int.

An invocation of this method of the form nextInt() behaves in exactly the same way as the invocation nextInt(radix), where radix 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 range
NoSuchElementException	if input is exhausted
IllegalStateException	if this scanner is closed

public int nextInt (int radix)

Scans the next token of the input as an int. This method will throw InputMismatchException 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 via Character.digit, prepending a negative sign (-) if the locale specific negative prefixes and suffixes were present, and passing the resulting string to Integer.parseInt with the specified radix.

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 range
NoSuchElementException	if input is exhausted
IllegalStateException	if this scanner is closed

public String 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 found
IllegalStateException	if this scanner is closed

public long nextLong ()

Scans the next token of the input as a long.

An invocation of this method of the form nextLong() behaves in exactly the same way as the invocation nextLong(radix), where radix 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 range
NoSuchElementException	if input is exhausted
IllegalStateException	if this scanner is closed

public long nextLong (int radix)

Scans the next token of the input as a long. This method will throw InputMismatchException 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 via Character.digit, prepending a negative sign (-) if the locale specific negative prefixes and suffixes were present, and passing the resulting string to Long.parseLong with the specified radix.

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 range
NoSuchElementException	if input is exhausted
IllegalStateException	if this scanner is closed

public short nextShort (int radix)

Scans the next token of the input as a short. This method will throw InputMismatchException 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 via Character.digit, prepending a negative sign (-) if the locale specific negative prefixes and suffixes were present, and passing the resulting string to Short.parseShort with the specified radix.

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 range
NoSuchElementException	if input is exhausted
IllegalStateException	if this scanner is closed

public short nextShort ()

Scans the next token of the input as a short.

An invocation of this method of the form nextShort() behaves in exactly the same way as the invocation nextShort(radix), where radix 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 range
NoSuchElementException	if input is exhausted
IllegalStateException	if this scanner is closed

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

public void remove ()

The remove operation is not supported by this implementation of Iterator.

Throws

UnsupportedOperationException	if this method is invoked.

See Also

• Iterator

public Scanner reset ()

Resets this scanner.

Resetting a scanner discards all of its explicit state information which may have been changed by invocations of useDelimiter(String), useLocale(Locale), or useRadix(int).

An invocation of this method of the form scanner.reset() behaves in exactly the same way as the invocation

scanner.useDelimiter("\\p{javaWhitespace}+")
          .useLocale(Locale.getDefault(Locale.Category.FORMAT))
          .useRadix(10);
 

Returns

• this scanner

public Scanner skip (String pattern)

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 invocation skip(Pattern.compile(pattern)).

Parameters

pattern	a string specifying the pattern to skip over

Returns

• this scanner

Throws

IllegalStateException	if this scanner is closed

public Scanner skip (Pattern pattern)

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 found
IllegalStateException	if this scanner is closed

public String toString ()

Returns the string representation of this Scanner. The string representation of a Scanner contains information that may be useful for debugging. The exact format is unspecified.

Returns

• The string representation of this scanner

public Scanner useDelimiter (Pattern pattern)

Sets this scanner's delimiting pattern to the specified pattern.

Parameters

pattern	A delimiting pattern

Returns

• this scanner

public Scanner useDelimiter (String pattern)

Sets this scanner's delimiting pattern to a pattern constructed from the specified String.

An invocation of this method of the form useDelimiter(pattern) behaves in exactly the same way as the invocation useDelimiter(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

public Scanner useLocale (Locale locale)

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

public Scanner useRadix (int radix)

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 than Character.MAX_RADIX, then an IllegalArgumentException is thrown.

Invoking the reset() method will set the scanner's radix to 10.

Parameters

radix	The radix to use when scanning numbers

Returns

• this scanner

Throws

IllegalArgumentException	if radix is out of range