HashMap.containsKey() method is used to check a key exits or not in hashmap. HashMap.containsKey() Method returns true if this map contains a mapping for the given key. More formally, returns true if and only if this map contains a mapping for a key k such that (key==null ? k==null : key.equals(k)).
(There can be at most one such mapping.)
Syntax :
public boolean containsKey(Object key) {
}Parameters – key key whose presence in this map is to be tested
Return Value – true if this map contains a mapping for the given key
Exception – Its throws following exception
ClassCastException – if the key is of an inappropriate type for this map (optional)
NullPointerException – if the specified key is null and this map does not permit null keys (optional)
import java.util.HashMap;
import java.util.Map;
public class HashMapSearchKey {
public static void main(String[] args) {
Map<Integer,String> hm = new HashMap<Integer,String>();
/*
* Associates the specified value with the specified key in
this map (optional operation). If the map previously
contained a mapping for the key, the old value is
replaced by the specified value
*/
hm.put(1,"ankush");
hm.put(2, "amit");
hm.put(3,"shivam");
hm.put(4,"ankit");
hm.put(5, "yogesh");
/*
* Returns true if this map contains a
* mapping for the specified key
*/
System.out.println("key 1 ="+hm.containsKey(1));
System.out.println("key 20 ="+hm.containsKey(20));
System.out.println("key 9 ="+hm.containsKey(9));
System.out.println("key 5 ="+ hm.containsKey(5));
}
}Output:
key 1 =true
key 20 =false
key 9 =false
key 5 =true