Scanner
This class is a text scanner or tokenizer. It can read input from any Readable object, and convenience constructors can read text from a specified string, file, byte stream, or byte channel. The constructors for files, byte streams, and byte channels optionally allow you to specify the name of the charset to use for byte-to-character conversions. After creating a Scanner , you can configure it. useDelimiter( ) specifies a regular expression (as a java.util.regex.Pattern or a String ) that represents the token delimiter. The default delimiter is any run of whitespace. useLocale( ) specifies the Locale to use for scanning numbers : this may affect things like the character expected for decimal points and the thousands separator. useRadix( ) specifies the radix, or base, in which numbers should be parsed. Any value between 2 and 36 is allowed. These configuration methods may be called at any time and are not required to be called before scanning begins. Scanner implements the Iterable<String> interface, and you can use the hasNext( ) and next ( ) methods of this interface to break the input into a series of String tokens separated by whitespace or by the delimiter specified with useDelimiter( ) . In addition to these Iterable methods, however, Scanner defines a number of next X and hasNext X methods for various numeric types X . nextLine( ) returns the next line of input. Two variants of the next( ) method accept a regular expression as an argument and return the next chunk of text matching a specified regular expression. The corresponding hasNext( ) methods accept a regular expression and return TRue if the input matches it. The skip( ) method ignores delimiters and skips text matching the specified regular expression. findInLine( ) looks ahead for text matching the specified regular expression in the current line. If a match is found, the Scanner advances past that text and returns it. Otherwise, the Scanner returns null without advancing. findWithinHorizon( ) is similar but looks for a match within the specified number of characters (a horizon of 0 specifies an unlimited number). The next( ) methods and its next X variants throw a NoSuchElementException if there is no more input text. They throw an InputMismatchException (a subclass of NoSuchElementException ) if the next token cannot be parsed as the specified type or does not match the specified pattern. The Readable object that the Scanner reads text from may throw a java.io.IOException , but, for ease of use, the Scanner never propagates this exception. If an IOException occurs, the Scanner assumes that no more input is available from the Readable . Call ioException( ) to obtain the most recent IOException , if any, thrown by the Readable . The close( ) method checks whether the Readable object implements the Closeable interface and, if so, calls the close( ) method on that object. Once close( ) has been called, any attempt to read tokens from the Scanner results in an IllegalStateException . See also StringTokenizer and java.io.StreamTokenizer . Figure 16-53. java.util.Scanner public final class Scanner implements Iterator<String> { // Public Constructors public Scanner (Readable source ); public Scanner (java.nio.channels.ReadableByteChannel source ); public Scanner (java.io.InputStream source ); public Scanner (java.io.File source ) throws java.io.FileNotFoundException; public Scanner (String source ); public Scanner (java.nio.channels.ReadableByteChannel source , String charsetName ); public Scanner (java.io.InputStream source , String charsetName ); public Scanner (java.io.File source , String charsetName ) throws java.io.FileNotFoundException; // Public Instance Methods public void close ( ); public java.util.regex.Pattern delimiter ( ); public String findInLine (String pattern ); public String findInLine (java.util.regex.Pattern pattern ); public String findWithinHorizon (java.util.regex.Pattern pattern , int horizon ); public String findWithinHorizon (String pattern , int horizon ); public boolean hasNext (java.util.regex.Pattern pattern ); public boolean hasNext (String pattern ); public boolean hasNextBigDecimal ( ); public boolean hasNextBigInteger ( ); public boolean hasNextBigInteger (int radix ); public boolean hasNextBoolean ( ); public boolean hasNextByte ( ); public boolean hasNextByte (int radix ); public boolean hasNextDouble ( ); public boolean hasNextFloat ( ); public boolean hasNextInt ( ); public boolean hasNextInt (int radix ); public boolean hasNextLine ( ); public boolean hasNextLong ( ); public boolean hasNextLong (int radix ); public boolean hasNextShort ( ); public boolean hasNextShort (int radix ); public java.io.IOException ioException ( ); public Locale locale ( ); public java.util.regex.MatchResult match ( ); public String next (String pattern ); public String next (java.util.regex.Pattern pattern ); public java.math.BigDecimal nextBigDecimal ( ); public java.math.BigInteger nextBigInteger ( ); public java.math.BigInteger nextBigInteger (int radix ); public boolean nextBoolean ( ); public byte nextByte ( ); public byte nextByte (int radix ); public double nextDouble ( ); public float nextFloat ( ); public int nextInt ( ); public int nextInt (int radix ); public String nextLine ( ); public long nextLong ( ); public long nextLong (int radix ); public short nextShort ( ); public short nextShort (int radix ); public int radix ( ); public Scanner skip (java.util.regex.Pattern pattern ); public Scanner skip (String pattern ); public Scanner useDelimiter (java.util.regex.Pattern pattern ); public Scanner useDelimiter (String pattern ); public Scanner useLocale (Locale locale ); public Scanner useRadix (int radix ); // Methods Implementing Iterator public boolean hasNext ( ); public String next ( ); public void remove ( ); // Public Methods Overriding Object public String toString ( ); }  |
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