The Collection Program Singleton used to return an immutable list containing only the specified object using SingletonList(T o) method

BACK

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

Example Program

import java.util.*;

public class List111 {
	public static void displayList(List<String> l) {
		Iterator<String> i = l.iterator();
		while (i.hasNext())
			System.out.print("\t" + i.next());
		System.out.println();
	}

	public static void main(String[] args) {
		String init[] = { "One", "Two", "Three", "One", "Two", "Three" };
		List<String> list = new ArrayList<String>(Arrays.asList(init));
		System.out.println("Size of 'List' :" + list.size());
		System.out.println("Before Singleton List apply");
		System.out.println("Contents of the list 'list':");
		displayList(list);
		System.out.println();
		list = Collections.singletonList("four");
		System.out.println("After Sigleton List applied ");
		System.out.println("Contents of the list 'list':");
		displayList(list);
		System.out.println("Size of 'List': " + list.size());
	}
}

Output:

Size of ‘List’ :6

Before Singleton List apply

Contents of the list ‘list':

One Two Three  One Two Three

After Sigleton List applied

Contents of the list ‘list':

four

Size of ‘List': 1

Explanation:

public static <T> List<T> singletonList(T o)

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

Parameters:

o – the sole object to be stored in the returned set.

Returns:

An immutable set containing only the specified object. The returned list is serializable.

Since:

1.3