symbol.java

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package Symbol;

public class Symbol {
  private String name;
  private Symbol(String n) { name = n; }
  private static java.util.Dictionary dict = new java.util.Hashtable();

  public String toString() { return name; }

  /**
   * Make return the unique symbol associated with a string.
   * Repeated calls to <tt>symbol("abc")</tt> will return the same Symbol.
   */
  public static Symbol symbol(String n) {
     String u = n.intern();
     Symbol s = (Symbol)dict.get(u);
     if (s==null) {
        s = new Symbol(u);
        dict.put(u,s);
     }
     return s;
  }
}