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Scanner.java
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Scanner.java
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/*
* Copyright (c) 2003, 2018, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*/
package java.util;
import java.io.*;
import java.math.*;
import java.nio.*;
import java.nio.channels.*;
import java.nio.charset.*;
import java.nio.file.Path;
import java.nio.file.Files;
import java.text.*;
import java.text.spi.NumberFormatProvider;
import java.util.function.Consumer;
import java.util.regex.*;
import java.util.stream.Stream;
import java.util.stream.StreamSupport;
import sun.util.locale.provider.LocaleProviderAdapter;
import sun.util.locale.provider.ResourceBundleBasedAdapter;
/**
* A simple text scanner which can parse primitive types and strings using
* regular expressions.
*
* <p>A {@code 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 {@code next} methods.
*
* <p>For example, this code allows a user to read a number from
* {@code System.in}:
* <blockquote><pre>{@code
* Scanner sc = new Scanner(System.in);
* int i = sc.nextInt();
* }</pre></blockquote>
*
* <p>As another example, this code allows {@code long} types to be
* assigned from entries in a file {@code myNumbers}:
* <blockquote><pre>{@code
* Scanner sc = new Scanner(new File("myNumbers"));
* while (sc.hasNextLong()) {
* long aLong = sc.nextLong();
* }
* }</pre></blockquote>
*
* <p>The scanner can also use delimiters other than whitespace. This
* example reads several items in from a string:
* <blockquote><pre>{@code
* 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();
* }</pre></blockquote>
* <p>
* prints the following output:
* <blockquote><pre>{@code
* 1
* 2
* red
* blue
* }</pre></blockquote>
*
* <p>The same output can be generated with this code, which uses a regular
* expression to parse all four tokens at once:
* <blockquote><pre>{@code
* 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();
* }</pre></blockquote>
*
* <p>The <a id="default-delimiter">default whitespace delimiter</a> used
* by a scanner is as recognized by {@link Character#isWhitespace(char)
* Character.isWhitespace()}. The {@link #reset reset()}
* method will reset the value of the scanner's delimiter to the default
* whitespace delimiter regardless of whether it was previously changed.
*
* <p>A scanning operation may block waiting for input.
*
* <p>The {@link #next} and {@link #hasNext} methods and their
* companion methods (such as {@link #nextInt} and
* {@link #hasNextInt}) first skip any input that matches the delimiter
* pattern, and then attempt to return the next token. Both {@code hasNext()}
* and {@code next()} methods may block waiting for further input. Whether a
* {@code hasNext()} method blocks has no connection to whether or not its
* associated {@code next()} method will block. The {@link #tokens} method
* may also block waiting for input.
*
* <p>The {@link #findInLine findInLine()},
* {@link #findWithinHorizon findWithinHorizon()},
* {@link #skip skip()}, and {@link #findAll 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.
*
* <p>When a scanner throws an {@link InputMismatchException}, the scanner
* will not pass the token that caused the exception, so that it may be
* retrieved or skipped via some other method.
*
* <p>Depending upon the type of delimiting pattern, empty tokens may be
* returned. For example, the pattern {@code "\\s+"} will return no empty
* tokens since it matches multiple instances of the delimiter. The delimiting
* pattern {@code "\\s"} could return empty tokens since it only passes one
* space at a time.
*
* <p> A scanner can read text from any object which implements the {@link
* java.lang.Readable} interface. If an invocation of the underlying
* readable's {@link java.lang.Readable#read read()} method throws an {@link
* java.io.IOException} then the scanner assumes that the end of the input
* has been reached. The most recent {@code IOException} thrown by the
* underlying readable can be retrieved via the {@link #ioException} method.
*
* <p>When a {@code Scanner} is closed, it will close its input source
* if the source implements the {@link java.io.Closeable} interface.
*
* <p>A {@code Scanner} is not safe for multithreaded use without
* external synchronization.
*
* <p>Unless otherwise mentioned, passing a {@code null} parameter into
* any method of a {@code Scanner} will cause a
* {@code NullPointerException} to be thrown.
*
* <p>A scanner will default to interpreting numbers as decimal unless a
* different radix has been set by using the {@link #useRadix} method. The
* {@link #reset} method will reset the value of the scanner's radix to
* {@code 10} regardless of whether it was previously changed.
*
* <h3> <a id="localized-numbers">Localized numbers</a> </h3>
*
* <p> 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
* <a id="initial-locale">initial locale </a>is the value returned by the {@link
* java.util.Locale#getDefault(Locale.Category)
* Locale.getDefault(Locale.Category.FORMAT)} method; it may be changed via the {@link
* #useLocale useLocale()} method. The {@link #reset} method will reset the value of the
* scanner's locale to the initial locale regardless of whether it was
* previously changed.
*
* <p>The localized formats are defined in terms of the following parameters,
* which for a particular locale are taken from that locale's {@link
* java.text.DecimalFormat DecimalFormat} object, {@code df}, and its and
* {@link java.text.DecimalFormatSymbols DecimalFormatSymbols} object,
* {@code dfs}.
*
* <blockquote><dl>
* <dt><i>LocalGroupSeparator </i>
* <dd>The character used to separate thousands groups,
* <i>i.e.,</i> {@code dfs.}{@link
* java.text.DecimalFormatSymbols#getGroupingSeparator
* getGroupingSeparator()}
* <dt><i>LocalDecimalSeparator </i>
* <dd>The character used for the decimal point,
* <i>i.e.,</i> {@code dfs.}{@link
* java.text.DecimalFormatSymbols#getDecimalSeparator
* getDecimalSeparator()}
* <dt><i>LocalPositivePrefix </i>
* <dd>The string that appears before a positive number (may
* be empty), <i>i.e.,</i> {@code df.}{@link
* java.text.DecimalFormat#getPositivePrefix
* getPositivePrefix()}
* <dt><i>LocalPositiveSuffix </i>
* <dd>The string that appears after a positive number (may be
* empty), <i>i.e.,</i> {@code df.}{@link
* java.text.DecimalFormat#getPositiveSuffix
* getPositiveSuffix()}
* <dt><i>LocalNegativePrefix </i>
* <dd>The string that appears before a negative number (may
* be empty), <i>i.e.,</i> {@code df.}{@link
* java.text.DecimalFormat#getNegativePrefix
* getNegativePrefix()}
* <dt><i>LocalNegativeSuffix </i>
* <dd>The string that appears after a negative number (may be
* empty), <i>i.e.,</i> {@code df.}{@link
* java.text.DecimalFormat#getNegativeSuffix
* getNegativeSuffix()}
* <dt><i>LocalNaN </i>
* <dd>The string that represents not-a-number for
* floating-point values,
* <i>i.e.,</i> {@code dfs.}{@link
* java.text.DecimalFormatSymbols#getNaN
* getNaN()}
* <dt><i>LocalInfinity </i>
* <dd>The string that represents infinity for floating-point
* values, <i>i.e.,</i> {@code dfs.}{@link
* java.text.DecimalFormatSymbols#getInfinity
* getInfinity()}
* </dl></blockquote>
*
* <h4> <a id="number-syntax">Number syntax</a> </h4>
*
* <p> 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).
*
* <dl>
* <dt><i>NonAsciiDigit</i>:
* <dd>A non-ASCII character c for which
* {@link java.lang.Character#isDigit Character.isDigit}{@code (c)}
* returns true
*
* <dt><i>Non0Digit</i>:
* <dd>{@code [1-}<i>Rmax</i>{@code ] | }<i>NonASCIIDigit</i>
*
* <dt><i>Digit</i>:
* <dd>{@code [0-}<i>Rmax</i>{@code ] | }<i>NonASCIIDigit</i>
*
* <dt><i>GroupedNumeral</i>:
* <dd><code>( </code><i>Non0Digit</i>
* <i>Digit</i>{@code ?
* }<i>Digit</i>{@code ?}
* <dd> <code>( </code><i>LocalGroupSeparator</i>
* <i>Digit</i>
* <i>Digit</i>
* <i>Digit</i>{@code )+ )}
*
* <dt><i>Numeral</i>:
* <dd>{@code ( ( }<i>Digit</i>{@code + )
* | }<i>GroupedNumeral</i>{@code )}
*
* <dt><a id="Integer-regex"><i>Integer</i>:</a>
* <dd>{@code ( [-+]? ( }<i>Numeral</i>{@code
* ) )}
* <dd>{@code | }<i>LocalPositivePrefix</i> <i>Numeral</i>
* <i>LocalPositiveSuffix</i>
* <dd>{@code | }<i>LocalNegativePrefix</i> <i>Numeral</i>
* <i>LocalNegativeSuffix</i>
*
* <dt><i>DecimalNumeral</i>:
* <dd><i>Numeral</i>
* <dd>{@code | }<i>Numeral</i>
* <i>LocalDecimalSeparator</i>
* <i>Digit</i>{@code *}
* <dd>{@code | }<i>LocalDecimalSeparator</i>
* <i>Digit</i>{@code +}
*
* <dt><i>Exponent</i>:
* <dd>{@code ( [eE] [+-]? }<i>Digit</i>{@code + )}
*
* <dt><a id="Decimal-regex"><i>Decimal</i>:</a>
* <dd>{@code ( [-+]? }<i>DecimalNumeral</i>
* <i>Exponent</i>{@code ? )}
* <dd>{@code | }<i>LocalPositivePrefix</i>
* <i>DecimalNumeral</i>
* <i>LocalPositiveSuffix</i>
* <i>Exponent</i>{@code ?}
* <dd>{@code | }<i>LocalNegativePrefix</i>
* <i>DecimalNumeral</i>
* <i>LocalNegativeSuffix</i>
* <i>Exponent</i>{@code ?}
*
* <dt><i>HexFloat</i>:
* <dd>{@code [-+]? 0[xX][0-9a-fA-F]*\.[0-9a-fA-F]+
* ([pP][-+]?[0-9]+)?}
*
* <dt><i>NonNumber</i>:
* <dd>{@code NaN
* | }<i>LocalNan</i>{@code
* | Infinity
* | }<i>LocalInfinity</i>
*
* <dt><i>SignedNonNumber</i>:
* <dd>{@code ( [-+]? }<i>NonNumber</i>{@code )}
* <dd>{@code | }<i>LocalPositivePrefix</i>
* <i>NonNumber</i>
* <i>LocalPositiveSuffix</i>
* <dd>{@code | }<i>LocalNegativePrefix</i>
* <i>NonNumber</i>
* <i>LocalNegativeSuffix</i>
*
* <dt><a id="Float-regex"><i>Float</i></a>:
* <dd><i>Decimal</i>
* {@code | }<i>HexFloat</i>
* {@code | }<i>SignedNonNumber</i>
*
* </dl>
* <p>Whitespace is not significant in the above regular expressions.
*
* @since 1.5
*/
// 扫描器，允许从指定的输入源读取数据
public final class Scanner implements Iterator<String>, Closeable {
/** Internal buffer used to hold input */
private CharBuffer buf;
/** Size of internal character buffer */
private static final int BUFFER_SIZE = 1024;
/** The index into the buffer currently held by the Scanner */
private int position;
/** Internal matcher used for finding delimiters */
private Matcher matcher;
/** Pattern used to delimit tokens */
private Pattern delimPattern;
/** Pattern found in last hasNext operation */
private Pattern hasNextPattern;
/** Position after last hasNext operation */
private int hasNextPosition;
/** Result after last hasNext operation */
private String hasNextResult;
/** The input source */
private Readable source;
/** Boolean is true if source is done */
private boolean sourceClosed = false;
/** Boolean indicating more input is required */
private boolean needInput = false;
/** Boolean indicating if a delim has been skipped this operation */
private boolean skipped = false;
/** A store of a position that the scanner may fall back to */
private int savedScannerPosition = -1;
/** A cache of the last primitive type scanned */
private Object typeCache = null;
/** Boolean indicating if a match result is available */
private boolean matchValid = false;
/** Boolean indicating if this scanner has been closed */
private boolean closed = false;
/** The current radix used by this scanner */
private int radix = 10;
/** The default radix for this scanner */
private int defaultRadix = 10;
/** The locale used by this scanner */
private Locale locale = null;
/** A cache of the last few recently used Patterns */
private PatternLRUCache patternCache = new PatternLRUCache(7);
/** A holder of the last IOException encountered */
private IOException lastException;
/**
* Number of times this scanner's state has been modified.
* Generally incremented on most public APIs and checked within spliterator implementations.
*/
int modCount;
/** A pattern for java whitespace */
private static Pattern WHITESPACE_PATTERN = Pattern.compile("\\p{javaWhitespace}+"); // Character.isWhitespace()
/** A pattern for any token */
private static Pattern FIND_ANY_PATTERN = Pattern.compile("(?s).*");
/** A pattern for non-ASCII digits */
private static Pattern NON_ASCII_DIGIT = Pattern.compile("[\\p{javaDigit}&&[^0-9]]");
// Fields and methods to support scanning primitive types
/**
* Locale dependent values used to scan numbers
*/
private String groupSeparator = "\\,";
private String decimalSeparator = "\\.";
private String nanString = "NaN";
private String infinityString = "Infinity";
private String positivePrefix = "";
private String negativePrefix = "\\-";
private String positiveSuffix = "";
private String negativeSuffix = "";
/**
* Fields and an accessor method to match booleans
*/
private static volatile Pattern boolPattern;
private static final String BOOLEAN_PATTERN = "true|false";
private static Pattern boolPattern() {
Pattern bp = boolPattern;
if(bp == null) {
boolPattern = bp = Pattern.compile(BOOLEAN_PATTERN, Pattern.CASE_INSENSITIVE);
}
return bp;
}
/**
* Fields and methods to match bytes, shorts, ints, and longs
*/
private Pattern integerPattern;
private String digits = "0123456789abcdefghijklmnopqrstuvwxyz";
private String non0Digit = "[\\p{javaDigit}&&[^0]]";
private int SIMPLE_GROUP_INDEX = 5;
private String buildIntegerPatternString() {
String radixDigits = digits.substring(0, radix);
// \\p{javaDigit} is not guaranteed to be appropriate
// here but what can we do? The final authority will be
// whatever parse method is invoked, so ultimately the
// Scanner will do the right thing
String digit = "((?i)[" + radixDigits + "]|\\p{javaDigit})";
String groupedNumeral = "(" + non0Digit + digit + "?" + digit + "?(" + groupSeparator + digit + digit + digit + ")+)";
// digit++ is the possessive form which is necessary for reducing
// backtracking that would otherwise cause unacceptable performance
String numeral = "(("+ digit+"++)|"+groupedNumeral+")";
String javaStyleInteger = "([-+]?(" + numeral + "))";
String negativeInteger = negativePrefix + numeral + negativeSuffix;
String positiveInteger = positivePrefix + numeral + positiveSuffix;
return "(" + javaStyleInteger + ")|(" + positiveInteger + ")|(" + negativeInteger + ")";
}
private Pattern integerPattern() {
if (integerPattern == null) {
integerPattern = patternCache.forName(buildIntegerPatternString());
}
return integerPattern;
}
/**
* Fields and an accessor method to match line separators
*/
private static volatile Pattern separatorPattern;
private static volatile Pattern linePattern;
private static final String LINE_SEPARATOR_PATTERN = "\r\n|[\n\r\u2028\u2029\u0085]";
private static final String LINE_PATTERN = ".*(" + LINE_SEPARATOR_PATTERN + ")|.+$";
private static Pattern separatorPattern() {
Pattern sp = separatorPattern;
if(sp == null) {
separatorPattern = sp = Pattern.compile(LINE_SEPARATOR_PATTERN);
}
return sp;
}
private static Pattern linePattern() {
Pattern lp = linePattern;
if(lp == null) {
linePattern = lp = Pattern.compile(LINE_PATTERN);
}
return lp;
}
/**
* Fields and methods to match floats and doubles
*/
private Pattern floatPattern;
private Pattern decimalPattern;
private void buildFloatAndDecimalPattern() {
// \\p{javaDigit} may not be perfect, see above
String digit = "([0-9]|(\\p{javaDigit}))";
String exponent = "([eE][+-]?" + digit + "+)?";
String groupedNumeral = "(" + non0Digit + digit + "?" + digit + "?(" + groupSeparator + digit + digit + digit + ")+)";
// Once again digit++ is used for performance, as above
String numeral = "((" + digit + "++)|" + groupedNumeral + ")";
String decimalNumeral = "(" + numeral + "|" + numeral + decimalSeparator + digit + "*+|" + decimalSeparator + digit + "++)";
String nonNumber = "(NaN|" + nanString + "|Infinity|" + infinityString + ")";
String positiveFloat = "(" + positivePrefix + decimalNumeral + positiveSuffix + exponent + ")";
String negativeFloat = "(" + negativePrefix + decimalNumeral + negativeSuffix + exponent + ")";
String decimal = "(([-+]?" + decimalNumeral + exponent + ")|" + positiveFloat + "|" + negativeFloat + ")";
String hexFloat = "[-+]?0[xX][0-9a-fA-F]*\\.[0-9a-fA-F]+([pP][-+]?[0-9]+)?";
String positiveNonNumber = "(" + positivePrefix + nonNumber + positiveSuffix + ")";
String negativeNonNumber = "(" + negativePrefix + nonNumber + negativeSuffix + ")";
String signedNonNumber = "(([-+]?" + nonNumber + ")|" + positiveNonNumber + "|" + negativeNonNumber + ")";
floatPattern = Pattern.compile(decimal + "|" + hexFloat + "|" + signedNonNumber);
decimalPattern = Pattern.compile(decimal);
}
private Pattern floatPattern() {
if(floatPattern == null) {
buildFloatAndDecimalPattern();
}
return floatPattern;
}
private Pattern decimalPattern() {
if(decimalPattern == null) {
buildFloatAndDecimalPattern();
}
return decimalPattern;
}
/*▼ 构造器 ████████████████████████████████████████████████████████████████████████████████┓ */
/*
* 扫描器的输入源是多样化的，包括：InputStream、File、Path、ReadableByteChannel、String、Readable。
* 解码字节流时可以指定预设的字符编码，也可以使用JVM默认的字符编码。
*/
/**
* Constructs a new {@code 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}.
*
* @param source An input stream to be scanned
*/
public Scanner(InputStream source) {
this(new InputStreamReader(source), WHITESPACE_PATTERN);
}
/**
* Constructs a new {@code Scanner} that produces values scanned
* from the specified input stream. Bytes from the stream are converted
* into characters using the specified charset.
*
* @param source An input stream to be scanned
* @param 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(InputStream source, String charsetName) {
this(source, toCharset(charsetName));
}
/**
* Constructs a new {@code Scanner} that produces values scanned
* from the specified input stream. Bytes from the stream are converted
* into characters using the specified charset.
*
* @param source an input stream to be scanned
* @param charset the charset used to convert bytes from the file
* into characters to be scanned
*
* @since 10
*/
public Scanner(InputStream source, Charset charset) {
this(makeReadable(Objects.requireNonNull(source, "source"), charset), WHITESPACE_PATTERN);
}
/**
* Constructs a new {@code 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}.
*
* @param source A file to be scanned
*
* @throws FileNotFoundException if source is not found
*/
public Scanner(File source) throws FileNotFoundException {
this(new FileInputStream(source).getChannel());
}
/**
* Constructs a new {@code Scanner} that produces values scanned
* from the specified file. Bytes from the file are converted into
* characters using the specified charset.
*
* @param source A file to be scanned
* @param charsetName The encoding type used to convert bytes from the file
* into characters to be scanned
*
* @throws FileNotFoundException if source is not found
* @throws IllegalArgumentException if the specified encoding is
* not found
*/
public Scanner(File source, String charsetName) throws FileNotFoundException {
this(Objects.requireNonNull(source), toDecoder(charsetName));
}
/**
* Constructs a new {@code Scanner} that produces values scanned
* from the specified file. Bytes from the file are converted into
* characters using the specified charset.
*
* @param source A file to be scanned
* @param charset 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
*/
public Scanner(File source, Charset charset) throws IOException {
this(Objects.requireNonNull(source), charset.newDecoder());
}
/**
* Constructs a new {@code 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}.
*
* @param source the path to the file to be scanned
*
* @throws IOException if an I/O error occurs opening source
* @since 1.7
*/
public Scanner(Path source) throws IOException {
this(Files.newInputStream(source));
}
/**
* Constructs a new {@code Scanner} that produces values scanned
* from the specified file. Bytes from the file are converted into
* characters using the specified charset.
*
* @param source the path to the file to be scanned
* @param charsetName The encoding type used to convert bytes from the file
* into characters to be scanned
*
* @throws IOException if an I/O error occurs opening source
* @throws IllegalArgumentException if the specified encoding is not found
* @since 1.7
*/
public Scanner(Path source, String charsetName) throws IOException {
this(Objects.requireNonNull(source), toCharset(charsetName));
}
/**
* Constructs a new {@code Scanner} that produces values scanned
* from the specified file. Bytes from the file are converted into
* characters using the specified charset.
*
* @param source the path to the file to be scanned
* @param charset 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
*/
public Scanner(Path source, Charset charset) throws IOException {
this(makeReadable(source, charset));
}
/**
* Constructs a new {@code 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}.
*
* @param source A channel to scan
*/
public Scanner(ReadableByteChannel source) {
this(makeReadable(Objects.requireNonNull(source, "source")), WHITESPACE_PATTERN);
}
/**
* Constructs a new {@code Scanner} that produces values scanned
* from the specified channel. Bytes from the source are converted into
* characters using the specified charset.
*
* @param source A channel to scan
* @param 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 Scanner(ReadableByteChannel source, String charsetName) {
this(makeReadable(Objects.requireNonNull(source, "source"), toDecoder(charsetName)), WHITESPACE_PATTERN);
}
/**
* Constructs a new {@code Scanner} that produces values scanned
* from the specified channel. Bytes from the source are converted into
* characters using the specified charset.
*
* @param source a channel to scan
* @param charset the encoding type used to convert bytes from the
* channel into characters to be scanned
*
* @since 10
*/
public Scanner(ReadableByteChannel source, Charset charset) {
this(makeReadable(Objects.requireNonNull(source, "source"), charset), WHITESPACE_PATTERN);
}
/**
* Constructs a new {@code Scanner} that produces values scanned
* from the specified string.
*
* @param source A string to scan
*/
public Scanner(String source) {
this(new StringReader(source), WHITESPACE_PATTERN);
}
/**
* Constructs a new {@code Scanner} that produces values scanned
* from the specified source.
*
* @param source A character source implementing the {@link Readable} interface
*/
public Scanner(Readable source) {
this(Objects.requireNonNull(source, "source"), WHITESPACE_PATTERN);
}
/**
* Constructs a {@code Scanner} that returns values scanned
* from the specified source delimited by the specified pattern.
*
* @param source A character source implementing the Readable interface
* @param pattern A delimiting pattern
*/
private Scanner(Readable source, Pattern pattern) {
assert source != null : "source should not be null";
assert pattern != null : "pattern should not be null";
this.source = source;
delimPattern = pattern;
buf = CharBuffer.allocate(BUFFER_SIZE);
buf.limit(0);
matcher = delimPattern.matcher(buf);
matcher.useTransparentBounds(true); // 使用透明边界
matcher.useAnchoringBounds(false); // 不使用锚点边界
useLocale(Locale.getDefault(Locale.Category.FORMAT));
}
private Scanner(File source, CharsetDecoder dec) throws FileNotFoundException {
this(makeReadable(new FileInputStream(source).getChannel(), dec));
}
/*▲ 构造器 ████████████████████████████████████████████████████████████████████████████████┛ */
/*▼ hasNext ████████████████████████████████████████████████████████████████████████████████┓ */
/**
* 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.
*
* @return true if and only if this scanner's next token is a valid
* boolean value
*
* @throws IllegalStateException if this scanner is closed
*/
// 判断下一个元素是否为boolean值
public boolean hasNextBoolean() {
return hasNext(boolPattern());
}
/**
* Returns true if the next token in this scanner's input can be
* interpreted as a byte value in the default radix using the
* {@link #nextByte} method. The scanner does not advance past any input.
*
* @return true if and only if this scanner's next token is a valid
* byte value
*
* @throws IllegalStateException if this scanner is closed
*/
// 判断下一个元素是否为byte值(10进制)
public boolean hasNextByte() {
return hasNextByte(defaultRadix);
}
/**
* Returns true if the next token in this scanner's input can be
* interpreted as a short value in the default radix using the
* {@link #nextShort} method. The scanner does not advance past any input.
*
* @return 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
*/
// 判断下一个元素是否为short值(10进制)
public boolean hasNextShort() {
return hasNextShort(defaultRadix);
}
/**
* Returns true if the next token in this scanner's input can be
* interpreted as an int value in the default radix using the
* {@link #nextInt} method. The scanner does not advance past any input.
*
* @return true if and only if this scanner's next token is a valid
* int value
*
* @throws IllegalStateException if this scanner is closed
*/
// 判断下一个元素是否为int值(10进制)
public boolean hasNextInt() {
return hasNextInt(defaultRadix);
}
/**
* Returns true if the next token in this scanner's input can be
* interpreted as a long value in the default radix using the
* {@link #nextLong} method. The scanner does not advance past any input.
*
* @return true if and only if this scanner's next token is a valid
* long value
*
* @throws IllegalStateException if this scanner is closed
*/
// 判断下一个元素是否为long值(10进制)
public boolean hasNextLong() {
return hasNextLong(defaultRadix);
}
/**
* Returns true if the next token in this scanner's input can be
* interpreted as a float value using the {@link #nextFloat}
* method. The scanner does not advance past any input.
*
* @return true if and only if this scanner's next token is a valid
* float value
*
* @throws IllegalStateException if this scanner is closed
*/
// 判断下一个元素是否为float值
public boolean hasNextFloat() {
setRadix(10);
boolean result = hasNext(floatPattern());
if(result) { // Cache it
try {
String s = processFloatToken(hasNextResult);
typeCache = Float.valueOf(Float.parseFloat(s));
} catch(NumberFormatException nfe) {
result = false;
}
}
return result;
}
/**
* Returns true if the next token in this scanner's input can be
* interpreted as a double value using the {@link #nextDouble}
* method. The scanner does not advance past any input.
*
* @return true if and only if this scanner's next token is a valid
* double value
*
* @throws IllegalStateException if this scanner is closed
*/
// 判断下一个元素是否为double值
public boolean hasNextDouble() {
setRadix(10);
boolean result = hasNext(floatPattern());
if(result) { // Cache it
try {
String s = processFloatToken(hasNextResult);
typeCache = Double.valueOf(Double.parseDouble(s));
} catch(NumberFormatException nfe) {
result = false;
}
}
return result;
}
/**
* Returns true if the next token in this scanner's input can be
* interpreted as a {@code BigInteger} in the default radix using the
* {@link #nextBigInteger} method. The scanner does not advance past any
* input.
*
* @return true if and only if this scanner's next token is a valid
* {@code BigInteger}
*
* @throws IllegalStateException if this scanner is closed
*/
// 判断下一个元素是否为BigInteger值(10进制)
public boolean hasNextBigInteger() {
return hasNextBigInteger(defaultRadix);
}
/**
* Returns true if the next token in this scanner's input can be
* interpreted as a {@code BigDecimal} using the
* {@link #nextBigDecimal} method. The scanner does not advance past any
* input.
*
* @return true if and only if this scanner's next token is a valid
* {@code BigDecimal}
*
* @throws IllegalStateException if this scanner is closed
*/
// 判断下一个元素是否为BigDecimal值
public boolean hasNextBigDecimal() {
setRadix(10);
boolean result = hasNext(decimalPattern());
if(result) { // Cache it
try {
String s = processFloatToken(hasNextResult);
typeCache = new BigDecimal(s);
} catch(NumberFormatException nfe) {
result = false;
}
}
return result;
}
/**
* Returns true if the next token in this scanner's input can be
* interpreted as a byte value in the specified radix using the
* {@link #nextByte} method. The scanner does not advance past any input.
*
* <p>If the radix is less than {@link Character#MIN_RADIX Character.MIN_RADIX}
* or greater than {@link Character#MAX_RADIX Character.MAX_RADIX}, then an
* {@code IllegalArgumentException} is thrown.
*
* @param radix the radix used to interpret the token as a byte value
*
* @return true if and only if this scanner's next token is a valid
* byte value
*
* @throws IllegalStateException if this scanner is closed
* @throws IllegalArgumentException if the radix is out of range
*/
// 判断下一个元素是否为byte值，进制由参数radix指定
public boolean hasNextByte(int radix) {
setRadix(radix);
boolean result = hasNext(integerPattern());
if(result) { // Cache it
try {
String s = (matcher.group(SIMPLE_GROUP_INDEX) == null) ? processIntegerToken(hasNextResult) : hasNextResult;
typeCache = Byte.parseByte(s, radix);
} catch(NumberFormatException nfe) {
result = false;
}
}
return result;
}
/**
* Returns true if the next token in this scanner's input can be
* interpreted as a short value in the specified radix using the
* {@link #nextShort} method. The scanner does not advance past any input.
*
* <p>If the radix is less than {@link Character#MIN_RADIX Character.MIN_RADIX}
* or greater than {@link Character#MAX_RADIX Character.MAX_RADIX}, then an
* {@code IllegalArgumentException} is thrown.
*
* @param radix the radix used to interpret the token as a short value
*
* @return 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
* @throws IllegalArgumentException if the radix is out of range
*/
// 判断下一个元素是否为short值，进制由参数radix指定
public boolean hasNextShort(int radix) {
setRadix(radix);
boolean result = hasNext(integerPattern());
if(result) { // Cache it
try {
String s = (matcher.group(SIMPLE_GROUP_INDEX) == null) ? processIntegerToken(hasNextResult) : hasNextResult;
typeCache = Short.parseShort(s, radix);
} catch(NumberFormatException nfe) {
result = false;
}
}
return result;
}
/**
* Returns true if the next token in this scanner's input can be
* interpreted as an int value in the specified radix using the
* {@link #nextInt} method. The scanner does not advance past any input.
*
* <p>If the radix is less than {@link Character#MIN_RADIX Character.MIN_RADIX}
* or greater than {@link Character#MAX_RADIX Character.MAX_RADIX}, then an
* {@code IllegalArgumentException} is thrown.
*
* @param radix the radix used to interpret the token as an int value
*
* @return true if and only if this scanner's next token is a valid
* int value
*
* @throws IllegalStateException if this scanner is closed
* @throws IllegalArgumentException if the radix is out of range
*/