InstanceOfJava

1.Basic Java example program to check particular key exists in hashmap

1. package com.javacheckkeyhashmap;
2.  
3. import java.util.Hashmap;
4. import java.util.Iterator;
5. import java.util.Map;
6. import java.util.Map.Entry;
7.  
8. public class HashmapExample{
9.  
10. public static void main(String[] args) {
11.   
12. //create an Hashmap object
13. HashMap<String, String> hashmap = new HashMap();
14.        
15. //Add key values pairs to hashmap
16.         
17. hashmap.put("1","One");
18. hashmap.put("2","Two");
19. hashmap.put("3","Three");
20. hashmap.put("4","Four");
21. hashmap.put("5","Five");
22. hashmap.put("6","Six");       
23.         
24.  
25.  /*
26.   To check whether a particular key exists in HashMap use
27.    boolean containsKey(Object key) method of HashMap class.
28.   containsKey(Object key) returns true if the HashMap contains mapping for specified key
29.   otherwise false.
30.  */
31.  
32. boolean isExists = hashmap.containsKey("4");
33. System.out.println("4 exists in HashMap ? : " + isExists);
34.     
35.  
36. if(!hashmap.isEmpty()){
37.  
38. Iterator it=hashmap.entrySet().iterator();
39.              
40. while(it.hasNext()){
41. 
    
42. Map.Entry obj=(Entry) it.next();
43. System.out.print(obj.getKey()+" ");
44. System.out.println(obj.getValue());
45.              
46. }           
47. }   
48.  
49. }
50.  
51. }
     

Output:

1. 4 exists in HashMap ? : true
2. 1 One
3. 2 Two
4. 3 Three
5. 4 Four
6. 5 Five
7. 6 Six