JDK14/Java14源码在线阅读

/*
 * Copyright (c) 2010, 2015, 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
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package jdk.nashorn.internal.parser;

import static jdk.nashorn.internal.parser.TokenKind.BINARY;
import static jdk.nashorn.internal.parser.TokenKind.BRACKET;
import static jdk.nashorn.internal.parser.TokenKind.FUTURE;
import static jdk.nashorn.internal.parser.TokenKind.FUTURESTRICT;
import static jdk.nashorn.internal.parser.TokenKind.IR;
import static jdk.nashorn.internal.parser.TokenKind.KEYWORD;
import static jdk.nashorn.internal.parser.TokenKind.LITERAL;
import static jdk.nashorn.internal.parser.TokenKind.SPECIAL;
import static jdk.nashorn.internal.parser.TokenKind.UNARY;

import java.util.Locale;

/**
 * Description of all the JavaScript tokens.
 */
@SuppressWarnings("javadoc")
public enum TokenType {
    ERROR                (SPECIAL,  null),
    EOF                  (SPECIAL,  null),
    EOL                  (SPECIAL,  null),
    COMMENT              (SPECIAL,  null),
    // comments of the form //@ foo=bar or //# foo=bar
    // These comments are treated as special instructions
    // to the lexer, parser or codegenerator.
    DIRECTIVE_COMMENT    (SPECIAL,  null),

    NOT            (UNARY,   "!",    14, false),
    NE             (BINARY,  "!=",    9, true),
    NE_STRICT      (BINARY,  "!==",   9, true),
    MOD            (BINARY,  "%",    13, true),
    ASSIGN_MOD     (BINARY,  "%=",    2, false),
    BIT_AND        (BINARY,  "&",     8, true),
    AND            (BINARY,  "&&",    5, true),
    ASSIGN_BIT_AND (BINARY,  "&=",    2, false),
    LPAREN         (BRACKET, "(",    16, true),
    RPAREN         (BRACKET, ")",     0, true),
    MUL            (BINARY,  "*",    13, true),
    ASSIGN_MUL     (BINARY,  "*=",    2, false),
    POS            (UNARY,   "+",    14, false),
    ADD            (BINARY,  "+",    12, true),
    INCPREFIX      (UNARY,   "++",   15, true),
    ASSIGN_ADD     (BINARY,  "+=",    2, false),
    COMMARIGHT     (BINARY,  ",",     1, true),
    NEG            (UNARY,   "-",    14, false),
    SUB            (BINARY,  "-",    12, true),
    DECPREFIX      (UNARY,   "--",   15, true),
    ASSIGN_SUB     (BINARY,  "-=",    2, false),
    PERIOD         (BRACKET, ".",    17, true),
    DIV            (BINARY,  "/",    13, true),
    ASSIGN_DIV     (BINARY,  "/=",    2, false),
    COLON          (BINARY,  ":"),
    SEMICOLON      (BINARY,  ";"),
    LT             (BINARY,  "<",    10, true),
    SHL            (BINARY,  "<<",   11, true),
    ASSIGN_SHL     (BINARY,  "<<=",   2, false),
    LE             (BINARY,  "<=",   10, true),
    ASSIGN         (BINARY,  "=",     2, false),
    EQ             (BINARY,  "==",    9, true),
    EQ_STRICT      (BINARY,  "===",   9, true),
    ARROW          (BINARY,  "=>",    2, true),
    GT             (BINARY,  ">",    10, true),
    GE             (BINARY,  ">=",   10, true),
    SAR            (BINARY,  ">>",   11, true),
    ASSIGN_SAR     (BINARY,  ">>=",   2, false),
    SHR            (BINARY,  ">>>",  11, true),
    ASSIGN_SHR     (BINARY,  ">>>=",  2, false),
    TERNARY        (BINARY,  "?",     3, false),
    LBRACKET       (BRACKET, "[",    17, true),
    RBRACKET       (BRACKET, "]",     0, true),
    BIT_XOR        (BINARY,  "^",     7, true),
    ASSIGN_BIT_XOR (BINARY,  "^=",    2, false),
    LBRACE         (BRACKET,  "{"),
    BIT_OR         (BINARY,  "|",     6, true),
    ASSIGN_BIT_OR  (BINARY,  "|=",    2, false),
    OR             (BINARY,  "||",    4, true),
    RBRACE         (BRACKET, "}"),
    BIT_NOT        (UNARY,   "~",     14, false),
    ELLIPSIS       (UNARY,   "..."),

    // ECMA 7.6.1.1 Keywords, 7.6.1.2 Future Reserved Words.
    // All other Java keywords are commented out.

//  ABSTRACT       (FUTURE,   "abstract"),
//  BOOLEAN        (FUTURE,   "boolean"),
    BREAK          (KEYWORD,  "break"),
//  BYTE           (FUTURE,   "byte"),
    CASE           (KEYWORD,  "case"),
    CATCH          (KEYWORD,  "catch"),
//  CHAR           (FUTURE,   "char"),
    CLASS          (FUTURE,   "class"),
    CONST          (KEYWORD,  "const"),
    CONTINUE       (KEYWORD,  "continue"),
    DEBUGGER       (KEYWORD,  "debugger"),
    DEFAULT        (KEYWORD,  "default"),
    DELETE         (UNARY,    "delete",     14, false),
    DO             (KEYWORD,  "do"),
//  DOUBLE         (FUTURE,   "double"),
//  EACH           (KEYWORD,  "each"),  // Contextual.
    ELSE           (KEYWORD,  "else"),
    ENUM           (FUTURE,   "enum"),
    EXPORT         (FUTURE,   "export"),
    EXTENDS        (FUTURE,   "extends"),
    FALSE          (LITERAL,  "false"),
//  FINAL          (FUTURE,   "final"),
    FINALLY        (KEYWORD,  "finally"),
//  FLOAT          (FUTURE,   "float"),
    FOR            (KEYWORD,  "for"),
    FUNCTION       (KEYWORD,  "function"),
//  GET            (KEYWORD,  "get"), // Contextual.
//  GOTO           (FUTURE,   "goto"),
    IF             (KEYWORD,   "if"),
    IMPLEMENTS     (FUTURESTRICT,   "implements"),
    IMPORT         (FUTURE,   "import"),
    IN             (BINARY,   "in",         10, true),
    INSTANCEOF     (BINARY,   "instanceof", 10, true),
//  INT            (FUTURE,   "int"),
    INTERFACE      (FUTURESTRICT,   "interface"),
    LET            (FUTURESTRICT,   "let"),
//  LONG           (FUTURE,   "long"),
//  NATIVE         (FUTURE,   "native"),
    NEW            (UNARY,    "new",        17, false),
    NULL           (LITERAL,  "null"),
    PACKAGE        (FUTURESTRICT,   "package"),
    PRIVATE        (FUTURESTRICT,   "private"),
    PROTECTED      (FUTURESTRICT,   "protected"),
    PUBLIC         (FUTURESTRICT,   "public"),
    RETURN         (KEYWORD,  "return"),
//  SET            (KEYWORD,  "set"), // Contextual.
//  SHORT          (FUTURE,   "short"),
    STATIC         (FUTURESTRICT,   "static"),
    SUPER          (FUTURE,   "super"),
    SWITCH         (KEYWORD,  "switch"),
//  SYNCHRONIZED   (FUTURE,   "synchronized"),
    THIS           (KEYWORD,  "this"),
    THROW          (KEYWORD,  "throw"),
//  THROWS         (FUTURE,   "throws"),
//  TRANSIENT      (FUTURE,   "transient"),
    TRUE           (LITERAL,  "true"),
    TRY            (KEYWORD,  "try"),
    TYPEOF         (UNARY,    "typeof",     14, false),
    VAR            (KEYWORD,  "var"),
    VOID           (UNARY,    "void",       14, false),
//  VOLATILE       (FUTURE,   "volatile"),
    WHILE          (KEYWORD,  "while"),
    WITH           (KEYWORD,  "with"),
    YIELD          (FUTURESTRICT,  "yield"),

    DECIMAL        (LITERAL,  null),
    HEXADECIMAL    (LITERAL,  null),
    OCTAL_LEGACY   (LITERAL,  null),
    OCTAL          (LITERAL,  null),
    BINARY_NUMBER  (LITERAL,  null),
    FLOATING       (LITERAL,  null),
    STRING         (LITERAL,  null),
    ESCSTRING      (LITERAL,  null),
    EXECSTRING     (LITERAL,  null),
    IDENT          (LITERAL,  null),
    REGEX          (LITERAL,  null),
    XML            (LITERAL,  null),
    OBJECT         (LITERAL,  null),
    ARRAY          (LITERAL,  null),
    TEMPLATE       (LITERAL,  null),
    TEMPLATE_HEAD  (LITERAL,  null),
    TEMPLATE_MIDDLE(LITERAL,  null),
    TEMPLATE_TAIL  (LITERAL,  null),

    DECPOSTFIX     (IR,       null),
    INCPOSTFIX     (IR,       null),
    SPREAD_ARGUMENT(IR,       null),
    SPREAD_ARRAY   (IR,       null),
    YIELD_STAR     (IR,       null);

    /** Next token kind in token lookup table. */
    private TokenType next;

    /** Classification of token. */
    private final TokenKind kind;

    /** Printable name of token. */
    private final String name;

    /** Operator precedence. */
    private final int precedence;

    /** Left associativity */
    private final boolean isLeftAssociative;

    /** Cache values to avoid cloning. */
    private static final TokenType[] values;

    TokenType(final TokenKind kind, final String name) {
        next              = null;
        this.kind         = kind;
        this.name         = name;
        precedence        = 0;
        isLeftAssociative = false;
    }

    TokenType(final TokenKind kind, final String name, final int precedence, final boolean isLeftAssociative) {
        next                   = null;
        this.kind              = kind;
        this.name              = name;
        this.precedence        = precedence;
        this.isLeftAssociative = isLeftAssociative;
    }

    /**
     * Determines if the token has greater precedence than other.
     *
     * @param other  Compare token.
     * @param isLeft Is to the left of the other.
     *
     * @return {@code true} if greater precedence.
     */
    public boolean needsParens(final TokenType other, final boolean isLeft) {
        return other.precedence != 0 &&
               (precedence > other.precedence ||
               precedence == other.precedence && isLeftAssociative && !isLeft);
    }

    /**
     * Determines if the type is a valid operator.
     *
     * @param noIn {@code true} if IN operator should be ignored.
     *
     * @return {@code true} if valid operator.
     */

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