Java WeakHashMap containsValue() Method

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Description

The Java WeakHashMap containsValue(Object value) method is used to return true if this map, maps one or more keys to the specified value.

Declaration

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

public boolean containsValue(Object value)

Parameters

value − The value is the input whose presence in this map is to be tested.

Return Value

The method call returns true if this map maps one or more keys to the specified value.

Exception

NA

Checking Presence of a Value in a WeakHashMap of Integer, Integer Pairs Example

The following example shows the usage of Java WeakHashMap containsValue() method to check if a value is present in a Map or not. We've created a Map object of Integer,Integer pairs. Then few entries are added, map is printed and using containsValue() we're checking about two values in the map.

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("Map contains 2 as value: " + newmap.containsValue(2));
      System.out.println("Map contains 4 as value: " + newmap.containsValue(4));
   }
}

Output

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

Initial map elements: {3=3, 2=2, 1=1}
Map contains 2 as value: true
Map contains 4 as value: false

Checking Presence of a Value in a WeakHashMap of Integer, String Pairs Example

The following example shows the usage of Java WeakHashMap containsValue() method to check if a value is present in a Map or not. We've created a Map object of Integer,String pairs. Then few entries are added, map is printed and using containsValue() we're checking about two values in the map.

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("Map contains tutorials as value: " + newmap.containsValue("tutorials"));
      System.out.println("Map contains java as value: " + newmap.containsValue("java"));
   }
}

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}
Map contains tutorials as value: true
Map contains java as value: false

Checking Presence of a Value in a WeakHashMap of Integer, Object Pairs Example

The following example shows the usage of Java WeakHashMap containsValue() method to check if a value is present in a Map or not. We've created a Map object of Integer,Student pair. Then few entries are added, map is printed and using containsValue() we're checking about two values in the map.

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("Map contains Robert as value: " + newmap.containsValue(new Student(2, "Robert")));
      System.out.println("Map contains Jene as value: " + newmap.containsValue(new Student(4, "Jene")));
   }
}
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 + " ]";
   }
   @Override
   public boolean equals(Object obj) {
      if(obj == null) return false;
      Student s = (Student)obj;
      return this.rollNo == s.rollNo && this.name.equalsIgnoreCase(s.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 ]}
Map contains Robert as value: true
Map contains Jene as value: false