1 /*
   2  * Copyright (c) 2015, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.  Oracle designates this
   8  * particular file as subject to the "Classpath" exception as provided
   9  * by Oracle in the LICENSE file that accompanied this code.
  10  *
  11  * This code is distributed in the hope that it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14  * version 2 for more details (a copy is included in the LICENSE file that
  15  * accompanied this code).
  16  *
  17  * You should have received a copy of the GNU General Public License version
  18  * 2 along with this work; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  */
  25 
  26 package jdk.nashorn.internal.runtime;
  27 
  28 import java.io.Serializable;
  29 import jdk.nashorn.internal.objects.NativeSymbol;
  30 
  31 /**
  32  * This class represents a unique, non-String Object property key as defined in ECMAScript 6.
  33  */
  34 public final class Symbol implements Serializable {
  35 
  36     private final String name;
  37 
  38     private static final long serialVersionUID = -2988436597549486913L;
  39 
  40     /**
  41      * Symbol constructor
  42      * @param name symbol name
  43      */
  44     public Symbol(final String name) {
  45         this.name = name;
  46     }
  47 
  48     @Override
  49     public String toString() {
  50         return "Symbol(" + name + ")";
  51     }
  52 
  53     /**
  54      * Return the symbol's name
  55      * @return the name
  56      */
  57     public final String getName() {
  58         return name;
  59     }
  60 
  61     private Object writeReplace() {
  62         // If this symbol is a globally registered one, replace it with a
  63         // GlobalSymbol in serialized stream.
  64         return NativeSymbol.keyFor(null, this) == name ? new GlobalSymbol(name) : this;
  65     }
  66 
  67     /**
  68      * Represents a globally registered (with NativeSymbol._for) symbol in the
  69      * serialized stream. Upon deserialization, it resolves to the globally
  70      * registered symbol.
  71      */
  72     private static class GlobalSymbol implements Serializable {
  73         private static final long serialVersionUID = 1L;
  74 
  75         private final String name;
  76 
  77         GlobalSymbol(final String name) {
  78             this.name = name;
  79         }
  80 
  81         private Object readResolve() {
  82             return NativeSymbol._for(null, name);
  83         }
  84     }
  85 }