Binary search trees - Data Structures and Problem Solving Using Java - page 752

1 /**
2 * Returns the value in the map associated with the key.
3 * @param key the key to search for.
4 * @return the value that matches the key or null
5 * if the key is not found. Since null values are allowed,
6 * checking if the return value is null may not
7 * be a safe way to ascertain if the key is present in the map.
8 */
9 public ValueType get( KeyType key )
10 {
11 Map.Entry<KeyType,ValueType> match = theSet.getMatch( makePair( key ) );
12
13 if( match == null )
14 return null;
15 else
16 return match.getValue( );
17 }
18
19 /**
20 * Adds the key value pair to the map, overriding the
21 * original value if the key was already present.
22 * @param key the key to insert.
23 * @param value the value to insert.
24 * @return the old value associated with the key, or
25 * null if the key was not present prior to this call.
26 */
27 public ValueType put( KeyType key, ValueType value )
28 {
29 Map.Entry<KeyType,ValueType> match = theSet.getMatch( makePair( key ) );
30
31 if( match != null )
32 return match.setValue( value );
33
34 theSet.add( makePair( key, value ) );
35 return null;
36 }
37
38 /**
39 * Remove the key and its value from the map.
40 * @param key the key to remove.
41 * @return the previous value associated with the key,
42 * or null if the key was not present prior to this call.
43 */
44 public ValueType remove( KeyType key )
45 {
46 ValueType oldValue = get( key );
47 if( oldValue != null )
48 theSet.remove( makePair( key ) );
49
50 return oldValue;
51 }
figure 19.79
Implementations of basic MapImpl methods