java.util.Collections.unmodifiableMap() Method

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Description

The unmodifiableMap() method is used to return an unmodifiable view of the specified map.

Declaration

Following is the declaration for java.util.Collections.unmodifiableMap() method.

public static <K,V> Map<K,V> unmodifiableMap(Map<? extends K,? extends V> m)

Parameters

m − This is the map for which an unmodifiable view is to be returned.

Return Value

• The method call returns an unmodifiable view of the specified map.

Exception

NA

Example

The following example shows the usage of java.util.Collections.unmodifiableMap()

package com.tutorialspoint;

import java.util.*;

public class CollectionsDemo {
   public static void main(String[] s) {
   
      //object hash table 
      Hashtable<String,String> table = new Hashtable<String,String>();

      // populate the table
      table.put("key1", "value1");
      table.put("key2", "value2");
      table.put("key3", "value3");

      System.out.println("Initial collection: "+table);

      // create unmodifiable map
      Map m = Collections.unmodifiableMap(table);

      // try to modify the collection
      m.put("key3", "value3");
   }
}

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

Initial collection: {key3=value3, key2=value2, key1=value1}
Exception in thread "main" java.lang.UnsupportedOperationException