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

java_util_collections.htm

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