Java IdentityHashMap containsValue() Method

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Description

The Java IdentityHashMap containsValue(Object value) method is used to test whether the specified object reference is a value in this identity hash map.

Declaration

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

public boolean containsValue(Object value)

Parameters

value − This is the possible value to be checked.

Return Value

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

Exception

NA

Checking Value to Exist in an IdentityHashMap of Integer, Integer Pair Example

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

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

      // 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: {2=2, 3=3, 1=1}
Map contains 2 as value: true
Map contains 4 as value: false

Checking Value to Exist in an IdentityHashMap of Integer, String Pair Example

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

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

      // 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: {2=point, 3=is best, 1=tutorials}
Map contains tutorials as value: true
Map contains java as value: false

Checking Value to Exist in an IdentityHashMap of Integer, Object Pair Example

The following example shows the usage of Java IdentityHashMap containsValue() method to check if a value is present in a Map or not. We've created a Map object of Integer,Student 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.IdentityHashMap;

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

      // 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: {1=[ 1, Julie ], 3=[ 3, Adam ], 2=[ 2, Robert ]}
Map contains Robert as value: false
Map contains Jene as value: false