Java WeakHashMap isEmpty() Method

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Description

The Java WeakHashMap isEmpty() method is used to return true if this map contains no key-value mappings

Declaration

Following is the declaration for java.util.WeakHashMap.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 Emptyness of a WeakHashMap of Integer, Integer Pairs Example

The following example shows the usage of Java WeakHashMap 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.WeakHashMap;

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

      // 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());
   }
}

Output

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

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

Checking Emptyness of a WeakHashMap of Integer, Strings Pairs Example

The following example shows the usage of Java WeakHashMap 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.WeakHashMap;

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

      // 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());
   }
}

Output

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

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

Checking emptyness of a WeakHashMap of Integer, Object Pairs Example

The following example shows the usage of Java WeakHashMap 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.WeakHashMap;

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

      // 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 + " ]";
   }
}

Output

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

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