Java IdentityHashMap hashCode() Method

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Description

The Java IdentityHashMap hashCode() method is used to get the hash code value for this map.

Declaration

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

public int hashCode()

Parameters

NA

Return Value

The method call returns the hash code value for this map.

Exception

NA

Getting HashCode of IdentityHashMap of Integer, Integer Pair Example

The following example shows the usage of Java IdentityHashMap hashCode() method to get a hashcode of a Map. We've created a Map object of Integer,Integer pairs. Then few entries are added, map is printed. Using hashCode() method, hashcode is retrieved and printed.

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("hashcode: " + newmap.hashCode());
   }    
}

Output

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

Initial map elements: {2=2, 3=3, 1=1}
hashcode: 0

Getting HashCode of IdentityHashMap of Integer, String Pair Example

The following example shows the usage of Java IdentityHashMap hashCode() method to get a hashcode of a Map. We've created a Map object of Integer,String pairs. Then few entries are added, map is printed. Using hashCode() method, hashcode is retrieved and printed.

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("hashcode: " + newmap.hashCode());
   }    
}

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}
hashcode: -1728962655

Getting HashCode of IdentityHashMap of Integer, Object Pair Example

The following example shows the usage of Java IdentityHashMap hashCode() method to get a hashcode of a Map. We've created a Map object of Integer,Student pairs. Then few entries are added, map is printed. Using hashCode() method, hashcode is retrieved and printed.

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("hashcode: " + newmap.hashCode());
   }    
}
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 int hashCode() {
      return rollNo + name.hashCode();
   }
}

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 ]}
hashcode: -740293765