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Java Collections unmodifiableMap() Method with Example

Collections Class unmodifiableMap() method: Here, we are going to learn about the unmodifiableMap() method of Collections Class with its syntax and example.
Submitted by Preeti Jain, on February 08, 2020

Collections Class unmodifiableMap() method

• unmodifiableMap() method is available in java.util package.
• unmodifiableMap() method is used to get a non-modifiable view of the given Map (map).
• unmodifiableMap() method is a static method, it is accessible with the class name and if we try to access the method with the class object then also we will not get any error.
• unmodifiableMap() method does not throw an exception at the time of returning unmodifiable view of the given map.

Syntax:

    public static Map unmodifiableMap(Map map);

Parameter(s):

• Map map – represents the map object for which a non-modifiable view is to be retrieved.

Return value:

The return type of this method is Map, it returns an unmodifiable view of the given map.

Example:

// Java program to demonstrate the example 
// of Map unmodifiableMap() method of collections

import java.util.*;

public class UnmodifiableMapOfCollections {
    public static void main(String args[]) {
        // Instantiates a linked hashmap object
        Map < Integer, String > lhm = new LinkedHashMap < Integer, String > ();
        
        // By using put() method is to add
        //objects in a linked hashmap 
        lhm.put(10, "C");
        lhm.put(20, "C++");
        lhm.put(30, "JAVA");
        lhm.put(40, "PHP");
        lhm.put(50, "SFDC");

        // Display Linked HashMap
        System.out.println("linked hashmap: " + lhm);

        // By using unmodifiableMap() method is to
        // represent the linked hashmap in unmodifiable view
        Map m = Collections.unmodifiableMap(lhm);

        //We will get an exception when we
        //try to add an object in an unmodifiable map

        /* mm.put(60,"COBOL");*/
    }
}

Output

linked hashmap: {10=C, 20=C++, 30=JAVA, 40=PHP, 50=SFDC}