Enum


1   package polyglot.util;
2   
3   import java.io.Serializable  ;
4   import java.io.ObjectInputStream  ;
5   import java.io.ObjectOutputStream  ;
6   import java.io.IOException  ;
7   import java.util.*;
8   
9   /** An enumerated type.  Enums are interned and can be compared with ==. */
10  public class Enum implements Serializable  
11  {
12      /** The name of the enum.  Used for debugging and interning. */
13      private String   name;
14  
15      /** The intern cache. */
16      private static Map cache = new HashMap();
17  
18      protected Enum(String   name) {
19      this.name = name;
20  
21          // intern the enum and make sure this one is unique
22          if (intern() != this) {
23              throw new InternalCompilerError("Duplicate enum \"" + name + "\"");
24          }
25      }
26  
27      /** For serialization. */
28      private Enum() { }
29  
30      public int hashCode() {
31          return name.hashCode();
32      }
33  
34      public boolean equals(Object   o) {
35      return this == o;
36      }
37  
38      public String   toString() {
39      return name;
40      }
41  
42      private static class EnumKey {
43      Enum   e;
44  
45      EnumKey(Enum   e) {
46          this.e = e;
47      }
48  
49      public boolean equals(Object   o) {
50          return o instanceof EnumKey
51              && e.name.equals(((EnumKey) o).e.name)
52              && e.getClass() == ((EnumKey) o).e.getClass();
53      }
54  
55      public int hashCode() {
56          return e.getClass().hashCode() ^ e.name.hashCode();
57      }
58  
59          public String   toString() {
60              return e.toString();
61          }
62      }
63  
64      public Enum   intern() {
65          EnumKey k = new EnumKey(this);
66  
67      Enum   e = (Enum  ) cache.get(k);
68  
69      if (e == null) {
70          cache.put(k, this);
71          return this;
72      }
73  
74      return e;
75      }
76  }
77
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