java.util.Collections.singleton() Method


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Description

The singleton(T) method is used to return an immutable set containing only the specified object.

Declaration

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

public static <T> Set<T> singleton(T o)

Parameters

  • o -- This is the sole object to be stored in the returned set.

Return Value

The method call returns an immutable set containing only the specified object.

Exception

  • NA

Example

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

package com.tutorialspoint;

import java.util.*;

public class CollectionsDemo {
   public static void main(String args[]) {
   // create an array of string objs
   String init[] = { "One", "Two", "Three", "One", "Two", "Three" };
      
   // create two lists
   List list1 = new ArrayList(Arrays.asList(init));
   List list2 = new ArrayList(Arrays.asList(init));
      
   // remove from list1
   list1.remove("One");
   System.out.println("List1 value: "+list1);
      
   // remove from list2 using singleton
   list2.removeAll(Collections.singleton("One"));		   
   System.out.println("The SingletonList is :"+list2);
   }
}

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

List1 value: [Two, Three, One, Two, Three]
The SingletonList is :[Two, Three, Two, Three]

java_util_collections.htm

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