Java IdentityHashMap size() Method

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Description

The Java IdentityHashMap size() method is used to get the number of key-value mappings in this identity hash map.

Declaration

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

 public int size() 

Parameters

NA

Return Value

The method call returns the number of key-value mappings in this map.

Exception

NA

Getting Size of an IdentityHashMap of Integer, Integer Pair Example

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

 package com.tutorialspoint; import java.util.IdentityHashMap; public class IdentityHashMapDemo { public static void main(String args[]) { // create identity map IdentityHashMap<Integer,Integer> newmap = new IdentityHashMap<>(); // populate identity map newmap.put(1, 1); newmap.put(2, 2); newmap.put(3, 3); System.out.println("Initial map elements: " + newmap); System.out.println("Size of the map: " + newmap.size()); } } 

Output

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

 Initial map elements: {2=2, 3=3, 1=1} Size of the map: 3 

Getting Size of an IdentityHashMap of Integer, String Pair Example

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

 package com.tutorialspoint; import java.util.IdentityHashMap; public class IdentityHashMapDemo { public static void main(String args[]) { // create identity map IdentityHashMap<Integer,String> newmap = new IdentityHashMap<>(); // populate identity map newmap.put(1, "tutorials"); newmap.put(2, "point"); newmap.put(3, "is best"); System.out.println("Initial map elements: " + newmap); System.out.println("Size of the map: " + newmap.size()); } } 

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} Size of the map: 3 

Getting Size of an IdentityHashMap of Integer, Object Pair Example

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

 package com.tutorialspoint; import java.util.IdentityHashMap; public class IdentityHashMapDemo { public static void main(String args[]) { // create identity map IdentityHashMap<Integer,Student> newmap = new IdentityHashMap<>(); // populate identity 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("Size of the map: " + newmap.size()); } } 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: {1=[ 1, Julie ], 3=[ 3, Adam ], 2=[ 2, Robert ]} Size of the map: 3