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Java IdentityHashMap isEmpty() Method

The isEmpty() method is used to test if this identity hash map contains no key-value mappings.

Following is the declaration for java.util.IdentityHashMap.isEmpty() method.

public boolean isEmpty()

NA

The method call returns 'true' if this identity hash map contains no key-value mappings.

NA

The following example shows the usage of Java IdentityHashMap isEmpty() method to check a Map if it is empty or not. We've created a Map object of Integer,Integer pairs. Then few entries are added, map is printed. Then map is checked using isEmpty() method. Using clear() method, map is cleared and printed again and checked again using isEmpty() method.

package com.tutorialspoint;

import java.util.IdentityHashMap;

public class IdentityHashMapDemo {
   public static void main(String args[]) {
      
      // create identity map
      IdentityHashMap<Integer,Integer> newmap = new IdentityHashMap<>();

      // populate identity map
      newmap.put(1, 1);
      newmap.put(2, 2);
      newmap.put(3, 3); 

      System.out.println("Initial map elements: " + newmap);
      System.out.println("Is map Empty: " + newmap.isEmpty());

      // clear hash map
      newmap.clear();

      System.out.println("Map elements after clear: " + newmap);
      System.out.println("Is map Empty: " + newmap.isEmpty());
   }    
}

Let us compile and run the above program, this will produce the following result.

Initial map elements: {2=2, 3=3, 1=1}
Is map Empty: false
Map elements after clear: {}
Is map Empty: true

The following example shows the usage of Java IdentityHashMap isEmpty() method to check a Map if it is empty or not. We've created a Map object of Integer,String pairs. Then few entries are added, map is printed. Then map is checked using isEmpty() method. Using clear() method, map is cleared and printed again and checked again using isEmpty() method.

package com.tutorialspoint;

import java.util.IdentityHashMap;

public class IdentityHashMapDemo {
   public static void main(String args[]) {
      
      // create identity map
      IdentityHashMap<Integer,String> newmap = new IdentityHashMap<>();

      // populate identity map
      newmap.put(1, "tutorials");
      newmap.put(2, "point");
      newmap.put(3, "is best"); 

      System.out.println("Initial map elements: " + newmap);
      System.out.println("Is map Empty: " + newmap.isEmpty());
      // clear hash map
      newmap.clear();

      System.out.println("Map elements after clear: " + newmap);
      System.out.println("Is map Empty: " + newmap.isEmpty());
   }    
}

Let us compile and run the above program, this will produce the following result.

Initial map elements: {2=point, 3=is best, 1=tutorials}
Is map Empty: false
Map elements after clear: {}
Is map Empty: true

The following example shows the usage of Java IdentityHashMap isEmpty() method to check a Map if it is empty or not. We've created a Map object of Integer,Student pairs. Then few entries are added, map is printed. Then map is checked using isEmpty() method. Using clear() method, map is cleared and printed again and checked again using isEmpty() method.

package com.tutorialspoint;

import java.util.IdentityHashMap;

public class IdentityHashMapDemo {
   public static void main(String args[]) {
      
      // create identity map
      IdentityHashMap<Integer,Student> newmap = new IdentityHashMap<>();

      // populate identity map
      newmap.put(1, new Student(1, "Julie"));
      newmap.put(2, new Student(2, "Robert"));
      newmap.put(3, new Student(3, "Adam"));

      System.out.println("Initial map elements: " + newmap);
      System.out.println("Is map Empty: " + newmap.isEmpty());

      // clear hash map
      newmap.clear();

      System.out.println("Map elements after clear: " + newmap);
      System.out.println("Is map Empty: " + newmap.isEmpty());
   }    
}
class Student {
   int rollNo;
   String name;

   Student(int rollNo, String name){
      this.rollNo = rollNo;
      this.name = name;
   }

   @Override
   public String toString() {
      return "[ " + this.rollNo + ", " + this.name + " ]";
   }
}

Let us compile and run the above program, this will produce the following result.

Initial map elements: {1=[ 1, Julie ], 3=[ 3, Adam ], 2=[ 2, Robert ]}
Is map Empty: false
Map elements after clear: {}
Is map Empty: true

java_util_identityhashmap.htm

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