Java Collections unmodifiableMap() Method

The unmodifiableMap() method of Java Collections class is used to get an unmodifiable view of the specified map.

Syntax

Following is the declaration of unmodifiableMap() method:

Parameter

Parameter	Description	Required/Optional
m	It is the map for which an unmodifiable view is to be returned.	Required

Returns

The unmodifiableMap() method returns an unmodifiable view of the specified map.

Exceptions

Example 1

import java.util.*;
public class CollectionsUnmodifiableMapExample1 {
    public static void main(String[] args) {
    	  //Create object of hash map and Add values in the map
        HashMap<String,String> map = new HashMap<String,String>();
        map.put("key1", "Java");
        map.put("key2", "Android");
        map.put("key3", "JavaScript");
        System.out.println("Initial collection: "+map);
        //Create unmodifiable map
        Map<String,String> map2 = Collections.unmodifiableMap(map);
        System.out.println("Unmodifiable Map: " + map2);       
        map.put("key4", "JavaTpoint");
        System.out.println("Unmodifiable Map after adding: " + map2);
        }
}

Test it Now

Output:

Initial collection: {key1=Java, key2=Android, key3=JavaScript}
Unmodifiable Map: {key1=Java, key2=Android, key3=JavaScript}
Unmodifiable Map after adding: {key1=Java, key2=Android, key3=JavaScript, key4=JavaTpoint}

Example 2

import java.util.*;
public class CollectionsUnmodifiableMapExample2 {
    public static void main(String[] args) {
    	  Map<Integer, String> map = new HashMap<>();
        map.put(1, "one");
        map.put(2, "two");
        System.out.println("Initial Unmodifiable Map: "+map);
        Map<Integer, String> map2 = Collections.unmodifiableMap(map);
        map2.put(3, "three");
        }
}

Test it Now

Output:

Initial Unmodifiable Map: {1=one, 2=two}
Exception in thread "main" java.lang.UnsupportedOperationException
	at java.base/java.util.Collections$UnmodifiableMap.put(Collections.java:1453)
	at myPackage.CollectionsUnmodifiableMapExample2.main(CollectionsUnmodifiableMapExample2.java:10)

Example 3

import java.util.*;
public class CollectionsUnmodifiableMapExample3 {
	public static void main(String[] args) {
		Map<Integer, Integer> map = new HashMap<>();
		map.put(1, 1001);
		map.put(2, 1002);
		map.put(3, 1003);
		map.put(4, 1004);
		map.put(5, 1005);
		System.out.println("Unmodifiable map: " + map);		
		Map<Integer, Integer> map2 = Collections.unmodifiableMap(map);	
	      map.remove(4, 1004);	    	     
    	      System.out.print("Unmodifiable map after remove(4, 1004): "+map2);
	      }
}

Test it Now

Output:

Unmodifiable map: {1=1001, 2=1002, 3=1003, 4=1004, 5=1005}
Unmodifiable map after remove(4, 1004): {1=1001, 2=1002, 3=1003, 5=1005}

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Java Collections unmodifiableMap() Method

Syntax

Parameter

Returns

Exceptions

Example 1

Example 2

Example 3

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