Alphabet


1   package ro.infoiasi.donald.compiler.lexer;
2   
3   import ro.infoiasi.donald.compiler.lexer.exceptions.*;
4   import java.util.*;
5   
6   /** An ordered set of symbols (characters) */
7   public class Alphabet implements Cloneable   {
8       /** An array with all the characters currently in the alphabet */
9       private ArrayList arr;
10      /** A map containing symbol(Char)-index(Integer) pairs used for
11      quickly obtaining the symbol index corresponding to a symbol */
12      private HashMap map;
13  
14      /** Constructs an empty alphabet */
15      public Alphabet() {
16          map = new HashMap();
17          arr = new ArrayList();
18      }
19  
20      /** Constructs an alphabet containing all the distinct symbols
21      in the specified string (in that particular order) */
22      public Alphabet(String   s) {
23          this();
24          for (int i = 0; i<s.length(); i++) {
25              addSymbol(s.charAt(i));
26          }
27      }
28  
29      /** Constructs an alphabet by copying an existing one  */
30      public Alphabet(Alphabet alpha) {
31          arr = (ArrayList)alpha.arr.clone();
32          map = (HashMap)alpha.map.clone();
33      }
34  
35      /** Creates and returns a clone of this object */
36      public Object   clone() {
37          return new Alphabet(this);
38      }
39  
40      /** Indicates whether some other object is "equal to" this one. */
41      public boolean equals(Object   obj) {
42          Alphabet alpha = (Alphabet)obj;
43          if (size() != alpha.size()) {
44              return false;
45          }
46          for (int i = 0; i<size(); i++) {
47              if (getSymbol(i).charValue() != getSymbol(i).charValue()) {
48                  return false;
49              }
50          }
51          return true;
52      }
53  
54      /** Returns the number of symbols in this alphabet */
55      public int size() {
56          return arr.size();
57      }
58  
59      /** Removes all symbols from this alphabet */
60      public void clear() {
61          arr.clear();
62          map.clear();
63      }
64  
65      /** Adds the specified character to this alpabet.
66      Once added symbols can only be removed with clear(). */
67      public void addSymbol(char ch) {
68          if (!containsSymbol(ch)) {
69              Character   cObj = new Character  (ch);
70              arr.add(cObj);
71              map.put(cObj, new Integer  (map.size()));
72          }
73      }
74  
75      /** Returns the symbol in the alphabet at the given index */
76      public Character   getSymbol(int index) {
77          return (Character  ) arr.get(index);
78      }
79  
80      /** Returns true if this alphabet contains the specified character. */
81      public boolean containsSymbol(char ch) {
82          return map.containsKey(new Character  (ch));
83      }
84  
85      /** Returns the index in the alphabet for the specified character. */
86      public int idxSymbol(char ch) {
87          Integer   i = (Integer  )map.get(new Character  (ch));
88          return i.intValue();
89      }
90  
91      /** Returns a string containg all the symbols of the alphabet
92      in the same order as they were added */
93      public String   toString() {
94          StringBuffer   sb = new StringBuffer  (size());
95          for (int i=0; i<size(); i++) {
96              sb.append((Character  )arr.get(i));
97          }
98          return new String  (sb);
99      }
100 
101     /** Prints the contents of the alphabet. [Debuging purpose] */
102     public void print() {
103         System.out.println("Size: " + size());
104         System.out.print("Array: ");
105         System.out.println(arr);
106         System.out.print("Map: ");
107         System.out.println(map.entrySet());
108     }
109 }
110
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