Java HashMap isEmpty() Method

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Description

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

Declaration

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

public boolean isEmpty()

Parameters

NA

Return Value

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

Exception

NA

Checking Map of Integer, Integer Pair to be empty Example

The following example shows the usage of Java HashMap isEmpty() method to check a Map if it is empty or not. We've created a Map object of Integer,Integer pair. 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.HashMap;

public class HashMapDemo {
   public static void main(String args[]) {
      
      // create hash map
      HashMap<Integer,Integer> newmap = new HashMap<>();

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

Checking Map of Integer, String Pair to be empty Example

The following example shows the usage of Java HashMap isEmpty() method to check a Map if it is empty or not. We've created a Map object of Integer,String pair. 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.HashMap;

public class HashMapDemo {
   public static void main(String args[]) {
      
      // create hash map
      HashMap<Integer,String> newmap = new HashMap<>();

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

Checking Map of Integer, Student Pair to be empty Example

The following example shows the usage of Java HashMap isEmpty() method to check a Map if it is empty or not. We've created a Map object of Integer,Student pair. 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.HashMap;

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

      // populate hash 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 ], 2=[ 2, Robert ], 3=[ 3, Adam ]}
Is map Empty: false
Map elements after clear: {}
Is map Empty: true