Java IdentityHashMap containsKey() method

The containsKey(Object key) method of the Java IdentityHashMap class is used to check whether the calling IdentityHashMap contains the specified key.

Syntax

Parameters

Key - The possible key which is to be checked in the IdentityHashMap.

Return

True, if the specified key is a key in the calling IdentityHashMap.

Example 1

import java.util.IdentityHashMap;

public class IdentityHashMapContainsKeyExample1 {
    public static void main(String[] args) {
   //Creating an object of IdentityHashMap class
   IdentityHashMap <String,Integer> map = new IdentityHashMap <String,Integer>(6);
   
   //Putting key-value pairs inside map
   map.put("Java", 1);
   map.put("is", 2);
   map.put("the", 3);
   map.put("best", 4);
   map.put("programming", 5);
   map.put("language", 6);
   
   //Creating an Object
   String str1 = "Java";
   String str2 = "Object";
   String str3 = "Programming";
   String str4 = "programming";
   
   //Checking if the specified key is present in the calling IdentityHashMap
   System.out.println(map.containsKey(str1));
   System.out.println(map.containsKey(str2));
   System.out.println(map.containsKey(str3));
   System.out.println(map.containsKey(str4));
}
}

Output:

true
false
false
true

Example 2

import java.util.IdentityHashMap;

class Student{
    private int roll;
    private String name;
    private int standard;
    
    public Student(int roll,String name,int standard){
        this.roll = roll;
        this.name = name;
        this.standard = standard;
    }
    
    public String disp(){
        return roll+" "+name+" "+standard;
    }
}

public class IdentityHashMapContainsKeyExample2 {
    public static void main(String[] args) {
        
        //Creating Objects of Student class
        Student stud1 = new Student(1 ,"Ram ",10);
        Student stud2 = new Student(2 ,"Shyam ",10);
        Student stud3 = new Student(3 ,"Aman ",12);
        Student stud4 = new Student(4 ,"Harsh ",12);
        
        //Creating an instance of IdentityHashMap
        IdentityHashMap<Integer,Student> map = new IdentityHashMap<Integer,Student>(5);
        
        //Inserting the Student class objects into IdentityHashMap
        map.put(1,stud1);
        map.put(2,stud2);
        map.put(3,stud3);
        map.put(4,stud4);
        
        System.out.println(map.containsKey(0));
        System.out.println(map.containsKey(1));
        System.out.println(map.containsKey(3));
        System.out.println(map.containsKey(5));
}
}

Output: