Java WeakHashMap put() Method

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Description

The Java WeakHashMap put(Object key,Object value) method is used to associate the specified value with the specified key in this map. If the map previously contained a mapping for this key, the old value is replaced by the new value.

Declaration

Following is the declaration for java.util.WeakHashMap.put() method.

public Object put(Object key,Object value)

Parameters

• key − This is the key with which the specified value is to be associated.

• value − This is the value to be associated with the specified key.

Return Value

The method call returns the previous value associated with the specified key, or null if there was no mapping for the key.

Exception

NA

Adding a Key-Value Pair to a WeakHashMap of Integer, Integer Pairs Example

The following example shows the usage of Java WeakHashMap put() method to put few values in a Map. We've created a Map object of Integer,Integer pairs. Then few entries are added using put() method and then map is printed.

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("Map elements: " + newmap);
   }
}

Output

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

Map elements: {3=3, 2=2, 1=1}

Adding a Key-Value Pair to a WeakHashMap of Integer, Strings Pairs Example

The following example shows the usage of Java WeakHashMap put() method to put few values in a Map. We've created a Map object of Integer,String pairs. Then few entries are added using put() method and then map is printed.

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("Map elements: " + newmap);
   }
}

Output

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

Map elements: {3=is best, 2=point, 1=tutorials}

Adding a Key-Value Pair to a WeakHashMap of Integer, Object Pairs Example

The following example shows the usage of Java WeakHashMap put() method to put few values in a Map. We've created a Map object of Integer,Student pairs. Then few entries are added using put() method and then map is printed.

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("Map elements: " + newmap);
   }
}
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.

Map elements: {3=[ 3, Adam ], 2=[ 2, Robert ], 1=[ 1, Julie ]}