HASHING - Introduction to Java Programming: Comprehensive Version - page 1003

9 map.put( "Smith" , 65 );
10
11 System.out.println( "Entries in map: " + map);
12
13 System.out.println( "The age for Lewis is " +
14 map.get( "Lewis" ));
15
16 System.out.println( "Is Smith in the map? " +
17 map.containsKey( "Smith" ));
18 System.out.println( "Is age 33 in the map? " +
19 map.containsValue( 33 ));
20
21 map.remove( "Smith" );
22 System.out.println( "Entries in map: " + map);
23
24 map.clear();
25 System.out.println( "Entries in map: " + map);
26 }
27 }

display entries

get value

is key in map?

is value in map?

remove entry

Entries in map: [[Anderson, 31][Smith, 65][Lewis, 29][Cook, 29]]
The age for Lewis is 29
Is Smith in the map? true
Is age 33 in the map? false
Entries in map: [[Anderson, 31][Lewis, 29][Cook, 29]]
Entries in map: []

The program creates a map using MyHashMap (line 4) and adds five entries into the map
(lines 5-9). Line 5 adds key Smith with value 30 and line 9 adds Smith with value 65 . The
latter value replaces the former value. The map actually has only four entries. The program
displays the entries in the map (line 11), gets a value for a key (line 14), checks whether the
map contains the key (line 17) and a value (line 19), removes an entry with the key Smith
(line 21), and redisplays the entries in the map (line 22). Finally, the program clears the map
(line 24) and displays an empty map (line 25).

27.20

✓ ✓

What is 1 << 30 in line 8 in Listing 27.2? What are the integers resulted from 1 << 1 ,
1 << 2 , and 1 << 3 ?

Check

Point

27.21

What are the integers resulted from 32 >> 1 , 32 >> 2 , 32 >> 3 , and 32 >> 4 ?

27.22

In Listing 27.2, will the program work if LinkedList is replaced by ArrayList ?
In Listing 27.2, how do you replace the code in lines 55-59 using one line of code?

27.23

Describe how the put(key, value) method is implemented in the MyHashMap
class.

27.24

In Listing 27.5, the supplementalHash method is declared static, can the hash
method be declared static?

27.25

Show the output of the following code.

MyMap<String, String> map = new MyHashMap<>();
map.put( "Texas" , "Dallas" );
map.put( "Oklahoma" , "Norman" );
map.put( "Texas" , "Austin" );
map.put( "Oklahoma" , "Tulsa" );

System.out.println(map.get( "Texas" ));
System.out.println(map.size());