Java IdentityHashMap clear() method

The clear() method of the Java IdentityHashMap class is used to remove all the key-value pairs from the calling IdentityHashMap. The IdentityHashMap will become empty after calling this method.

Syntax

Example 1

import java.util.IdentityHashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;

public class IdentityHashMapClearExample1 {
    public static void main(String[] args) {
   //Creating an object of IdentityHashMap class
   IdentityHashMap <String,Integer> map = new IdentityHashMap <String,Integer>(5);
   
   //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);
   
   //Get a set of all entries
   Set set = map.entrySet();
   
   //Declare an iterator
   Iterator itr = set.iterator();
   
   //Displaying all the entries
   while(itr.hasNext())
   {
       Map.Entry m = (Map.Entry)itr.next();
       System.out.print(m.getKey()+"->");
       System.out.println(m.getValue());
   }
   
   //Clearing the Map
   map.clear();
   
   //Checking if the Map is empty
   System.out.println(map.isEmpty());
}
}

Test it Now

Output:

is->2
best->4
Java->1
the->3
language->6
programming->5
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 IdentityHashMapClearExample2 {
    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);
        
        //Checking if IdentityHashMap is not empty
        System.out.println(map.isEmpty());
        
        //Clearing the IdentityHashMap
        map.clear();
        
        //Now checking if the map is empty
        System.out.println(map.isEmpty());    
}
}

Test it Now

Output:

false
true

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