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Character.java
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Character.java
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/*
* Copyright (c) 2002, 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.lang;
import jdk.internal.HotSpotIntrinsicCandidate;
import java.util.Arrays;
import java.util.HashMap;
import java.util.Locale;
import java.util.Map;
/**
* The {@code Character} class wraps a value of the primitive
* type {@code char} in an object. An object of type
* {@code Character} contains a single field whose type is
* {@code char}.
* <p>
* In addition, this class provides several methods for determining
* a character's category (lowercase letter, digit, etc.) and for converting
* characters from uppercase to lowercase and vice versa.
* <p>
* Character information is based on the Unicode Standard, version 10.0.0.
* <p>
* The methods and data of class {@code Character} are defined by
* the information in the <i>UnicodeData</i> file that is part of the
* Unicode Character Database maintained by the Unicode
* Consortium. This file specifies various properties including name
* and general category for every defined Unicode code point or
* character range.
* <p>
* The file and its description are available from the Unicode Consortium at:
* <ul>
* <li><a href="http://www.unicode.org">http://www.unicode.org</a>
* </ul>
*
* <h3><a id="unicode">Unicode Character Representations</a></h3>
*
* <p>The {@code char} data type (and therefore the value that a
* {@code Character} object encapsulates) are based on the
* original Unicode specification, which defined characters as
* fixed-width 16-bit entities. The Unicode Standard has since been
* changed to allow for characters whose representation requires more
* than 16 bits. The range of legal <em>code point</em>s is now
* U+0000 to U+10FFFF, known as <em>Unicode scalar value</em>.
* (Refer to the <a
* href="http://www.unicode.org/reports/tr27/#notation"><i>
* definition</i></a> of the U+<i>n</i> notation in the Unicode
* Standard.)
*
* <p><a id="BMP">The set of characters from U+0000 to U+FFFF</a> is
* sometimes referred to as the <em>Basic Multilingual Plane (BMP)</em>.
* <a id="supplementary">Characters</a> whose code points are greater
* than U+FFFF are called <em>supplementary character</em>s. The Java
* platform uses the UTF-16 representation in {@code char} arrays and
* in the {@code String} and {@code StringBuffer} classes. In
* this representation, supplementary characters are represented as a pair
* of {@code char} values, the first from the <em>high-surrogates</em>
* range, (\uD800-\uDBFF), the second from the
* <em>low-surrogates</em> range (\uDC00-\uDFFF).
*
* <p>A {@code char} value, therefore, represents Basic
* Multilingual Plane (BMP) code points, including the surrogate
* code points, or code units of the UTF-16 encoding. An
* {@code int} value represents all Unicode code points,
* including supplementary code points. The lower (least significant)
* 21 bits of {@code int} are used to represent Unicode code
* points and the upper (most significant) 11 bits must be zero.
* Unless otherwise specified, the behavior with respect to
* supplementary characters and surrogate {@code char} values is
* as follows:
*
* <ul>
* <li>The methods that only accept a {@code char} value cannot support
* supplementary characters. They treat {@code char} values from the
* surrogate ranges as undefined characters. For example,
* {@code Character.isLetter('\u005CuD840')} returns {@code false}, even though
* this specific value if followed by any low-surrogate value in a string
* would represent a letter.
*
* <li>The methods that accept an {@code int} value support all
* Unicode characters, including supplementary characters. For
* example, {@code Character.isLetter(0x2F81A)} returns
* {@code true} because the code point value represents a letter
* (a CJK ideograph).
* </ul>
*
* <p>In the Java SE API documentation, <em>Unicode code point</em> is
* used for character values in the range between U+0000 and U+10FFFF,
* and <em>Unicode code unit</em> is used for 16-bit
* {@code char} values that are code units of the <em>UTF-16</em>
* encoding. For more information on Unicode terminology, refer to the
* <a href="http://www.unicode.org/glossary/">Unicode Glossary</a>.
*
* @author Lee Boynton
* @author Guy Steele
* @author Akira Tanaka
* @author Martin Buchholz
* @author Ulf Zibis
* @since 1.0
*/
/*
* char的包装类
*
* 一个有用的链接：https://www.oracle.com/technetwork/articles/java/supplementary-142654.html
*
* Character的局限性是：对于四字节的符号（其实也不是一个char）无法包装（但可以根据其码点值解码为字符串）。
*/
public final class Character implements java.io.Serializable, Comparable<Character> {
/*▼ Unicode符号分类代号 ████████████████████████████████████████████████████████████████████████████████┓ */
/**
* General category "Lu" in the Unicode specification.
*
* @since 1.1
*/
public static final byte UPPERCASE_LETTER = 1; // Lu - Letter, uppercase
/**
* General category "Ll" in the Unicode specification.
*
* @since 1.1
*/
public static final byte LOWERCASE_LETTER = 2; // Ll - Letter, lowercase
/**
* General category "Lt" in the Unicode specification.
*
* @since 1.1
*/
public static final byte TITLECASE_LETTER = 3; // Lt - Letter, titlecase
/**
* General category "Lm" in the Unicode specification.
*
* @since 1.1
*/
public static final byte MODIFIER_LETTER = 4; // Lm - Letter, modifier
/**
* General category "Lo" in the Unicode specification.
*
* @since 1.1
*/
public static final byte OTHER_LETTER = 5; // Lo - Letter, other
/**
* General category "Mn" in the Unicode specification.
*
* @since 1.1
*/
public static final byte NON_SPACING_MARK = 6; // Mn - Mark, nonspacing
/**
* General category "Me" in the Unicode specification.
*
* @since 1.1
*/
public static final byte ENCLOSING_MARK = 7; // Me - Mark, enclosing
/**
* General category "Mc" in the Unicode specification.
*
* @since 1.1
*/
public static final byte COMBINING_SPACING_MARK = 8; // Mc - Mark, spacing combining
/**
* General category "Nd" in the Unicode specification.
*
* @since 1.1
*/
public static final byte DECIMAL_DIGIT_NUMBER = 9; // Nd - Number, decimal digit
/**
* General category "Nl" in the Unicode specification.
*
* @since 1.1
*/
public static final byte LETTER_NUMBER = 10; // Nl - Number, letter
/**
* General category "No" in the Unicode specification.
*
* @since 1.1
*/
public static final byte OTHER_NUMBER = 11; // No - Number, other
/**
* General category "Pd" in the Unicode specification.
*
* @since 1.1
*/
public static final byte DASH_PUNCTUATION = 20; // Pd - Punctuation, dash
/**
* General category "Ps" in the Unicode specification.
*
* @since 1.1
*/
public static final byte START_PUNCTUATION = 21; // Ps - Punctuation, open
/**
* General category "Pe" in the Unicode specification.
*
* @since 1.1
*/
public static final byte END_PUNCTUATION = 22; // Pe - Punctuation, close
/**
* General category "Pc" in the Unicode specification.
*
* @since 1.1
*/
public static final byte CONNECTOR_PUNCTUATION = 23; // Pc - Punctuation, connector
/**
* General category "Po" in the Unicode specification.
*
* @since 1.1
*/
public static final byte OTHER_PUNCTUATION = 24; // Po - Punctuation, other
/**
* General category "Pi" in the Unicode specification.
*
* @since 1.4
*/
public static final byte INITIAL_QUOTE_PUNCTUATION = 29; // Pi - Punctuation, initial quote
/**
* General category "Pf" in the Unicode specification.
*
* @since 1.4
*/
public static final byte FINAL_QUOTE_PUNCTUATION = 30; // Pf - Punctuation, final quote
/**
* General category "Sm" in the Unicode specification.
*
* @since 1.1
*/
public static final byte MATH_SYMBOL = 25; // Sm - Symbol, math
/**
* General category "Sc" in the Unicode specification.
*
* @since 1.1
*/
public static final byte CURRENCY_SYMBOL = 26; // Sc - Symbol, currency
/**
* General category "Sk" in the Unicode specification.
*
* @since 1.1
*/
public static final byte MODIFIER_SYMBOL = 27; // Sk - Symbol, modifier
/**
* General category "So" in the Unicode specification.
*
* @since 1.1
*/
public static final byte OTHER_SYMBOL = 28; // So - Symbol, other
/**
* General category "Zs" in the Unicode specification.
*
* @since 1.1
*/
public static final byte SPACE_SEPARATOR = 12; // Zs - Separator, space
/**
* General category "Zl" in the Unicode specification.
*
* @since 1.1
*/
public static final byte LINE_SEPARATOR = 13; // Zl - Separator, line
/**
* General category "Zp" in the Unicode specification.
*
* @since 1.1
*/
public static final byte PARAGRAPH_SEPARATOR = 14; // Zp - Separator, paragraph
/**
* General category "Cn" in the Unicode specification.
*
* @since 1.1
*/
public static final byte UNASSIGNED = 0; // Cn - Other, not assigned
/**
* General category "Cc" in the Unicode specification.
*
* @since 1.1
*/
public static final byte CONTROL = 15; // Cc - Other, control
/**
* General category "Cf" in the Unicode specification.
*
* @since 1.1
*/
public static final byte FORMAT = 16; // Cf - Other, format
/**
* General category "Co" in the Unicode specification.
*
* @since 1.1
*/
public static final byte PRIVATE_USE = 18; // Co - Other, private use
/**
* General category "Cs" in the Unicode specification.
*
* @since 1.1
*/
public static final byte SURROGATE = 19; // Cs - Other, surrogate
/*▲ Unicode符号分类代号 ████████████████████████████████████████████████████████████████████████████████┛ */
/*▼ Unicode双向字符类型 ████████████████████████████████████████████████████████████████████████████████┓ */
/**
* Undefined bidirectional character type. Undefined {@code char}
* values have undefined directionality in the Unicode specification.
*
* @since 1.4
*/
public static final byte DIRECTIONALITY_UNDEFINED = -1; // 未定义
/**
* Strong bidirectional character type "L" in the Unicode specification.
*
* @since 1.4
*/
public static final byte DIRECTIONALITY_LEFT_TO_RIGHT = 0; // Left-to-Right
/**
* Strong bidirectional character type "R" in the Unicode specification.
*
* @since 1.4
*/
public static final byte DIRECTIONALITY_RIGHT_TO_LEFT = 1; // Right-to-Left
/**
* Strong bidirectional character type "AL" in the Unicode specification.
*
* @since 1.4
*/
public static final byte DIRECTIONALITY_RIGHT_TO_LEFT_ARABIC = 2; // Arabic Letter
/**
* Weak bidirectional character type "EN" in the Unicode specification.
*
* @since 1.4
*/
public static final byte DIRECTIONALITY_EUROPEAN_NUMBER = 3; // European Number
/**
* Weak bidirectional character type "ES" in the Unicode specification.
*
* @since 1.4
*/
public static final byte DIRECTIONALITY_EUROPEAN_NUMBER_SEPARATOR = 4; // European Separator
/**
* Weak bidirectional character type "ET" in the Unicode specification.
*
* @since 1.4
*/
public static final byte DIRECTIONALITY_EUROPEAN_NUMBER_TERMINATOR = 5; // European Number Terminator
/**
* Weak bidirectional character type "AN" in the Unicode specification.
*
* @since 1.4
*/
public static final byte DIRECTIONALITY_ARABIC_NUMBER = 6; // Arabic Number
/**
* Weak bidirectional character type "CS" in the Unicode specification.
*
* @since 1.4
*/
public static final byte DIRECTIONALITY_COMMON_NUMBER_SEPARATOR = 7; // Common Number Separator
/**
* Weak bidirectional character type "NSM" in the Unicode specification.
*
* @since 1.4
*/
public static final byte DIRECTIONALITY_NONSPACING_MARK = 8; // Nonspacing Mark
/**
* Weak bidirectional character type "BN" in the Unicode specification.
*
* @since 1.4
*/
public static final byte DIRECTIONALITY_BOUNDARY_NEUTRAL = 9; // Boundary Neutral
/**
* Neutral bidirectional character type "B" in the Unicode specification.
*
* @since 1.4
*/
public static final byte DIRECTIONALITY_PARAGRAPH_SEPARATOR = 10; // Paragraph Separator
/**
* Neutral bidirectional character type "S" in the Unicode specification.
*
* @since 1.4
*/
public static final byte DIRECTIONALITY_SEGMENT_SEPARATOR = 11; // Segment Separator
/**
* Neutral bidirectional character type "WS" in the Unicode specification.
*
* @since 1.4
*/
public static final byte DIRECTIONALITY_WHITESPACE = 12; // Whitespace
/**
* Neutral bidirectional character type "ON" in the Unicode specification.
*
* @since 1.4
*/
public static final byte DIRECTIONALITY_OTHER_NEUTRALS = 13; // Other Neutrals
/**
* Strong bidirectional character type "LRE" in the Unicode specification.
*
* @since 1.4
*/
public static final byte DIRECTIONALITY_LEFT_TO_RIGHT_EMBEDDING = 14; // Left-to-Right Embedding
/**
* Strong bidirectional character type "LRO" in the Unicode specification.
*
* @since 1.4
*/
public static final byte DIRECTIONALITY_LEFT_TO_RIGHT_OVERRIDE = 15; // Left-to-Right Override
/**
* Strong bidirectional character type "RLE" in the Unicode specification.
*
* @since 1.4
*/
public static final byte DIRECTIONALITY_RIGHT_TO_LEFT_EMBEDDING = 16; // Right-to-Left Embedding
/**
* Strong bidirectional character type "RLO" in the Unicode specification.
*
* @since 1.4
*/
public static final byte DIRECTIONALITY_RIGHT_TO_LEFT_OVERRIDE = 17; // Right-to-Left Override
/**
* Weak bidirectional character type "PDF" in the Unicode specification.
*
* @since 1.4
*/
public static final byte DIRECTIONALITY_POP_DIRECTIONAL_FORMAT = 18; // Pop Directional Format
/**
* Weak bidirectional character type "LRI" in the Unicode specification.
*
* @since 9
*/
public static final byte DIRECTIONALITY_LEFT_TO_RIGHT_ISOLATE = 19; // Left-to-Right Isolate
/**
* Weak bidirectional character type "RLI" in the Unicode specification.
*
* @since 9
*/
public static final byte DIRECTIONALITY_RIGHT_TO_LEFT_ISOLATE = 20; // Right-to-Left Isolate
/**
* Weak bidirectional character type "FSI" in the Unicode specification.
*
* @since 9
*/
public static final byte DIRECTIONALITY_FIRST_STRONG_ISOLATE = 21; // First Strong Isolate
/**
* Weak bidirectional character type "PDI" in the Unicode specification.
*
* @since 9
*/
public static final byte DIRECTIONALITY_POP_DIRECTIONAL_ISOLATE = 22; // Pop Directional Isolate
/*▲ Unicode双向字符类型 ████████████████████████████████████████████████████████████████████████████████┛ */
/**
* The minimum radix available for conversion to and from strings.
* The constant value of this field is the smallest value permitted for the radix argument in radix-conversion methods such as the {@code digit} method,
* the {@code forDigit} method, and the {@code toString} method of class {@code Integer}.
*
* @see Character#digit(char, int)
* @see Character#forDigit(int, int)
* @see Integer#toString(int, int)
* @see Integer#valueOf(String)
*/
// 进制转换约束下限，最小2进制
public static final int MIN_RADIX = 2;
/**
* The maximum radix available for conversion to and from strings.
* The constant value of this field is the largest value permitted
* for the radix argument in radix-conversion methods such as the
* {@code digit} method, the {@code forDigit} method, and the
* {@code toString} method of class {@code Integer}.
*
* @see Character#digit(char, int)
* @see Character#forDigit(int, int)
* @see Integer#toString(int, int)
* @see Integer#valueOf(String)
*/
// 进制转换约束上限，最大36进制，因为10个数字+26个字母的限制
public static final int MAX_RADIX = 36;
/**
* The constant value of this field is the smallest value of type {@code char}, {@code '\u005Cu0000'}.
*
* @since 1.0.2
*/
// char的最小值，Unicode基本平面区码点最小值
public static final char MIN_VALUE = '\u0000';
/**
* The constant value of this field is the largest value of type {@code char}, {@code '\u005CuFFFF'}.
*
* @since 1.0.2
*/
// char的最大值，Unicode基本平面区码点最大值
public static final char MAX_VALUE = '\uFFFF';
/**
* The {@code Class} instance representing the primitive type {@code char}.
*
* @since 1.1
*/
// 基本类型char的包装类实例
@SuppressWarnings("unchecked")
public static final Class<Character> TYPE = (Class<Character>) Class.getPrimitiveClass("char");
/**
* The minimum value of a <a href="http://www.unicode.org/glossary/#code_point"> Unicode code point</a>, constant {@code U+0000}.
*
* @since 1.5
*/
public static final int MIN_CODE_POINT = 0x000000; // Unicode码点最小值
/**
* The maximum value of a <a href="http://www.unicode.org/glossary/#code_point"> Unicode code point</a>, constant {@code U+10FFFF}.
*
* @since 1.5
*/
public static final int MAX_CODE_POINT = 0x10FFFF; // Unicode码点最大值
/**
* The minimum value of a <a href="http://www.unicode.org/glossary/#supplementary_code_point"> Unicode supplementary code point</a>, constant {@code U+10000}.
*
* @since 1.5
*/
public static final int MIN_SUPPLEMENTARY_CODE_POINT = 0x010000; // Unicode非基本平面区码点最小值
/**
* The minimum value of a <a href="http://www.unicode.org/glossary/#high_surrogate_code_unit"> Unicode high-surrogate code unit</a> in the UTF-16 encoding, constant {@code '\u005CuD800'}.
* A high-surrogate is also known as a <i>leading-surrogate</i>.
*
* @since 1.5
*/
public static final char MIN_HIGH_SURROGATE = '\uD800'; // 高代理区[U+D800~U+DBFF]的左边界
/**
* The maximum value of a <a href="http://www.unicode.org/glossary/#high_surrogate_code_unit"> Unicode high-surrogate code unit</a> in the UTF-16 encoding, constant {@code '\u005CuDBFF'}.
* A high-surrogate is also known as a <i>leading-surrogate</i>.
*
* @since 1.5
*/
public static final char MAX_HIGH_SURROGATE = '\uDBFF'; // 高代理区[U+D800~U+DBFF]的右边界
/**
* The minimum value of a <a href="http://www.unicode.org/glossary/#low_surrogate_code_unit"> Unicode low-surrogate code unit</a> in the UTF-16 encoding, constant {@code '\u005CuDC00'}.
* A low-surrogate is also known as a <i>trailing-surrogate</i>.
*
* @since 1.5
*/
public static final char MIN_LOW_SURROGATE = '\uDC00'; // 低代理区[U+DC00~U+DFFF]的左边界
/**
* The maximum value of a <a href="http://www.unicode.org/glossary/#low_surrogate_code_unit"> Unicode low-surrogate code unit</a> in the UTF-16 encoding, constant {@code '\u005CuDFFF'}.
* A low-surrogate is also known as a <i>trailing-surrogate</i>.
*
* @since 1.5
*/
public static final char MAX_LOW_SURROGATE = '\uDFFF'; // 低代理区[U+DC00~U+DFFF]的右边界
/**
* The minimum value of a Unicode surrogate code unit in the UTF-16 encoding, constant {@code '\u005CuD800'}.
*
* @since 1.5
*/
public static final char MIN_SURROGATE = MIN_HIGH_SURROGATE; // Unicode高代理区下限
/**
* The maximum value of a Unicode surrogate code unit in the UTF-16 encoding, constant {@code '\u005CuDFFF'}.
*
* @since 1.5
*/
public static final char MAX_SURROGATE = MAX_LOW_SURROGATE; // Unicode低代理区上限
/**
* The number of bits used to represent a {@code char} value in unsigned binary form, constant {@code 16}.
*
* @since 1.5
*/
public static final int SIZE = 16; // （无符号）char所占的位数
/**
* The number of bytes used to represent a {@code char} value in unsigned binary form.
*
* @since 1.8
*/
public static final int BYTES = SIZE / Byte.SIZE; // （无符号）char所占的字节数
/**
* Error flag. Use int (code point) to avoid confusion with U+FFFF.
*/
static final int ERROR = 0xFFFFFFFF; // 错误标记
/**
* use serialVersionUID from JDK 1.0.2 for interoperability
*/
private static final long serialVersionUID = 3786198910865385080L;
/**
* The value of the {@code Character}.
*
* @serial
*/
private final char value; // Character包装的值
/**
* Constructs a newly allocated {@code Character} object that represents the specified {@code char} value.
*
* @param value the value to be represented by the {@code Character} object.
*
* @deprecated It is rarely appropriate to use this constructor.
* The static factory {@link #valueOf(char)} is generally a better choice, as it is likely to yield significantly better space and time performance.
*/
// 过时，用valueOf替代。但如果不想使用[0, 127]范围内的字符缓存对象，则可以调用此方法。
@Deprecated(since = "9")
public Character(char value) {
this.value = value;
}
/*▼ 装箱/拆箱 ████████████████████████████████████████████████████████████████████████████████┓ */
/**
* Returns a {@code Character} instance representing the specified {@code char} value.
* If a new {@code Character} instance is not required, this method should generally be used in preference to the constructor {@link #Character(char)},
* as this method is likely to yield significantly better space and time performance by caching frequently requested values.
*
* This method will always cache values in the range {@code '\u005Cu0000'} to {@code '\u005Cu007F'}, inclusive, and may cache other values outside of this range.
*
* @param c a char value.
*
* @return a {@code Character} instance representing {@code c}.
*
* @since 1.5
*/
// 装箱，返回char的包装类实例。如果char范围在[0, 127]内，则使用缓存
@HotSpotIntrinsicCandidate
public static Character valueOf(char c) {
if(c <= 127) { // must cache
return CharacterCache.cache[(int) c];
}
return new Character(c);
}
/**
* Returns the value of this {@code Character} object.
*
* @return the primitive {@code char} value represented by
* this object.
*/
// 拆箱，将Character对象转为char值
@HotSpotIntrinsicCandidate
public char charValue() {
return value;
}
/*▲ 装箱/拆箱 ████████████████████████████████████████████████████████████████████████████████┛ */
/*▼ 判断字符属性 ████████████████████████████████████████████████████████████████████████████████┓ */
/**
* Determines if the specified character (Unicode code point) is an alphabet.
* <p>
* A character is considered to be alphabetic if its general category type,
* provided by {@link Character#getType(int) getType(codePoint)}, is any of
* the following:
* <ul>
* <li> {@code UPPERCASE_LETTER}
* <li> {@code LOWERCASE_LETTER}
* <li> {@code TITLECASE_LETTER}
* <li> {@code MODIFIER_LETTER}
* <li> {@code OTHER_LETTER}
* <li> {@code LETTER_NUMBER}
* </ul>
* or it has contributory property Other_Alphabetic as defined by the
* Unicode Standard.
*
* @param codePoint the character (Unicode code point) to be tested.
*
* @return {@code true} if the character is a Unicode alphabet
* character, {@code false} otherwise.
*
* @since 1.7
*/
// true：该字符是字母[Alphabetic]字符
public static boolean isAlphabetic(int codePoint) {
return (((((1 << Character.UPPERCASE_LETTER)
| (1 << Character.LOWERCASE_LETTER)
| (1 << Character.TITLECASE_LETTER)
| (1 << Character.MODIFIER_LETTER)
| (1 << Character.OTHER_LETTER)
| (1 << Character.LETTER_NUMBER)) >> getType(codePoint)) & 1) != 0)
|| CharacterData.of(codePoint).isOtherAlphabetic(codePoint);
}
/**
* Determines if the specified character (Unicode code point) is a CJKV (Chinese, Japanese, Korean and Vietnamese) ideograph, as defined by the Unicode Standard.
*
* @param codePoint the character (Unicode code point) to be tested.
*
* @return {@code true} if the character is a Unicode ideograph
* character, {@code false} otherwise.
*
* @since 1.7
*/
// true：该字符是表意字符
public static boolean isIdeographic(int codePoint) {
return CharacterData.of(codePoint).isIdeographic(codePoint);
}
/**
* Determines if the specified character is
* permissible as the first character in a Java identifier.
* <p>
* A character may start a Java identifier if and only if
* one of the following conditions is true:
* <ul>
* <li> {@link #isLetter(char) isLetter(ch)} returns {@code true}
* <li> {@link #getType(char) getType(ch)} returns {@code LETTER_NUMBER}
* <li> {@code ch} is a currency symbol (such as {@code '$'})
* <li> {@code ch} is a connecting punctuation character (such as {@code '_'}).
* </ul>
*
* <p><b>Note:</b> This method cannot handle <a
* href="#supplementary"> supplementary characters</a>. To support
* all Unicode characters, including supplementary characters, use
* the {@link #isJavaIdentifierStart(int)} method.
*
* @param ch the character to be tested.
*
* @return {@code true} if the character may start a Java identifier;
* {@code false} otherwise.
*
* @see Character#isJavaIdentifierPart(char)
* @see Character#isLetter(char)
* @see Character#isUnicodeIdentifierStart(char)
* @see javax.lang.model.SourceVersion#isIdentifier(CharSequence)
* @since 1.1
*/
// true：该字符可位于Java标识符起始位置
public static boolean isJavaIdentifierStart(char ch) {
return isJavaIdentifierStart((int) ch);
}
/**
* Determines if the character (Unicode code point) is
* permissible as the first character in a Java identifier.
* <p>
* A character may start a Java identifier if and only if
* one of the following conditions is true:
* <ul>
* <li> {@link #isLetter(int) isLetter(codePoint)}
* returns {@code true}
* <li> {@link #getType(int) getType(codePoint)}
* returns {@code LETTER_NUMBER}
* <li> the referenced character is a currency symbol (such as {@code '$'})
* <li> the referenced character is a connecting punctuation character
* (such as {@code '_'}).
* </ul>
*
* @param codePoint the character (Unicode code point) to be tested.
*
* @return {@code true} if the character may start a Java identifier;
* {@code false} otherwise.
*
* @see Character#isJavaIdentifierPart(int)
* @see Character#isLetter(int)
* @see Character#isUnicodeIdentifierStart(int)
* @see javax.lang.model.SourceVersion#isIdentifier(CharSequence)
* @since 1.5
*/
// true：该字符可位于Java标识符起始位置
public static boolean isJavaIdentifierStart(int codePoint) {
return CharacterData.of(codePoint).isJavaIdentifierStart(codePoint);
}
/**
* Determines if the specified character may be part of a Java
* identifier as other than the first character.
* <p>
* A character may be part of a Java identifier if any of the following
* are true:
* <ul>
* <li> it is a letter
* <li> it is a currency symbol (such as {@code '$'})
* <li> it is a connecting punctuation character (such as {@code '_'})
* <li> it is a digit
* <li> it is a numeric letter (such as a Roman numeral character)
* <li> it is a combining mark
* <li> it is a non-spacing mark
* <li> {@code isIdentifierIgnorable} returns
* {@code true} for the character
* </ul>
*
* <p><b>Note:</b> This method cannot handle <a
* href="#supplementary"> supplementary characters</a>. To support
* all Unicode characters, including supplementary characters, use
* the {@link #isJavaIdentifierPart(int)} method.
*
* @param ch the character to be tested.
*
* @return {@code true} if the character may be part of a
* Java identifier; {@code false} otherwise.
*
* @see Character#isIdentifierIgnorable(char)
* @see Character#isJavaIdentifierStart(char)
* @see Character#isLetterOrDigit(char)
* @see Character#isUnicodeIdentifierPart(char)
* @see javax.lang.model.SourceVersion#isIdentifier(CharSequence)
* @since 1.1
*/
// true：该字符可位于Java标识符的非起始部分
public static boolean isJavaIdentifierPart(char ch) {
return isJavaIdentifierPart((int) ch);
}
/**
* Determines if the character (Unicode code point) may be part of a Java
* identifier as other than the first character.
* <p>
* A character may be part of a Java identifier if any of the following
* are true:
* <ul>
* <li> it is a letter
* <li> it is a currency symbol (such as {@code '$'})
* <li> it is a connecting punctuation character (such as {@code '_'})
* <li> it is a digit
* <li> it is a numeric letter (such as a Roman numeral character)
* <li> it is a combining mark
* <li> it is a non-spacing mark
* <li> {@link #isIdentifierIgnorable(int)
* isIdentifierIgnorable(codePoint)} returns {@code true} for
* the character
* </ul>
*
* @param codePoint the character (Unicode code point) to be tested.
*
* @return {@code true} if the character may be part of a
* Java identifier; {@code false} otherwise.
*
* @see Character#isIdentifierIgnorable(int)
* @see Character#isJavaIdentifierStart(int)
* @see Character#isLetterOrDigit(int)
* @see Character#isUnicodeIdentifierPart(int)
* @see javax.lang.model.SourceVersion#isIdentifier(CharSequence)
* @since 1.5
*/
// true：该字符可位于Java标识符的非起始部分
public static boolean isJavaIdentifierPart(int codePoint) {
return CharacterData.of(codePoint).isJavaIdentifierPart(codePoint);
}
/**
* Determines if the specified character is permissible as the
* first character in a Unicode identifier.
* <p>
* A character may start a Unicode identifier if and only if
* one of the following conditions is true:
* <ul>
* <li> {@link #isLetter(char) isLetter(ch)} returns {@code true}
* <li> {@link #getType(char) getType(ch)} returns
* {@code LETTER_NUMBER}.
* </ul>
*
* <p><b>Note:</b> This method cannot handle <a
* href="#supplementary"> supplementary characters</a>. To support
* all Unicode characters, including supplementary characters, use
* the {@link #isUnicodeIdentifierStart(int)} method.
*
* @param ch the character to be tested.
*
* @return {@code true} if the character may start a Unicode
* identifier; {@code false} otherwise.
*
* @see Character#isJavaIdentifierStart(char)
* @see Character#isLetter(char)
* @see Character#isUnicodeIdentifierPart(char)
* @since 1.1
*/
// true：该字符可位于Unicode标识符的起始部分
public static boolean isUnicodeIdentifierStart(char ch) {
return isUnicodeIdentifierStart((int) ch);
}
/**
* Determines if the specified character (Unicode code point) is permissible as the
* first character in a Unicode identifier.
* <p>
* A character may start a Unicode identifier if and only if
* one of the following conditions is true:
* <ul>
* <li> {@link #isLetter(int) isLetter(codePoint)}
* returns {@code true}
* <li> {@link #getType(int) getType(codePoint)}
* returns {@code LETTER_NUMBER}.
* </ul>
*
* @param codePoint the character (Unicode code point) to be tested.
*
* @return {@code true} if the character may start a Unicode
* identifier; {@code false} otherwise.
*
* @see Character#isJavaIdentifierStart(int)
* @see Character#isLetter(int)
* @see Character#isUnicodeIdentifierPart(int)
* @since 1.5
*/
// true：该字符可位于Unicode标识符的起始部分
public static boolean isUnicodeIdentifierStart(int codePoint) {
return CharacterData.of(codePoint).isUnicodeIdentifierStart(codePoint);
}
/**
* Determines if the specified character may be part of a Unicode
* identifier as other than the first character.
* <p>
* A character may be part of a Unicode identifier if and only if
* one of the following statements is true:
* <ul>
* <li> it is a letter
* <li> it is a connecting punctuation character (such as {@code '_'})
* <li> it is a digit
* <li> it is a numeric letter (such as a Roman numeral character)
* <li> it is a combining mark
* <li> it is a non-spacing mark
* <li> {@code isIdentifierIgnorable} returns
* {@code true} for this character.
* </ul>
*
* <p><b>Note:</b> This method cannot handle <a
* href="#supplementary"> supplementary characters</a>. To support
* all Unicode characters, including supplementary characters, use
* the {@link #isUnicodeIdentifierPart(int)} method.
*
* @param ch the character to be tested.
*
* @return {@code true} if the character may be part of a
* Unicode identifier; {@code false} otherwise.
*
* @see Character#isIdentifierIgnorable(char)
* @see Character#isJavaIdentifierPart(char)
* @see Character#isLetterOrDigit(char)
* @see Character#isUnicodeIdentifierStart(char)
* @since 1.1
*/
// true：该字符可位于Unicode标识符的非起始部分
public static boolean isUnicodeIdentifierPart(char ch) {
return isUnicodeIdentifierPart((int) ch);
}
/**
* Determines if the specified character (Unicode code point) may be part of a Unicode
* identifier as other than the first character.
* <p>
* A character may be part of a Unicode identifier if and only if
* one of the following statements is true:
* <ul>
* <li> it is a letter
* <li> it is a connecting punctuation character (such as {@code '_'})
* <li> it is a digit
* <li> it is a numeric letter (such as a Roman numeral character)
* <li> it is a combining mark
* <li> it is a non-spacing mark
* <li> {@code isIdentifierIgnorable} returns
* {@code true} for this character.
* </ul>
*
* @param codePoint the character (Unicode code point) to be tested.
*
* @return {@code true} if the character may be part of a
* Unicode identifier; {@code false} otherwise.
*
* @see Character#isIdentifierIgnorable(int)
* @see Character#isJavaIdentifierPart(int)
* @see Character#isLetterOrDigit(int)
* @see Character#isUnicodeIdentifierStart(int)
* @since 1.5