Java Tutorial/Collections/Prebuilt Collections

Empty Collections

The Collections class provides three constants to represent empty collections

   <source lang="java">

public static final List EMPTY_LIST public static final Map EMPTY_MAP public static final Set EMPTY_SET</source>

Singleton Collections

   <source lang="java">

import java.util.Collections; public class MainClass{

 public static void main(String[] a){
    System.out.println(Collections.singletonList("a")); 
    System.out.println(Collections.singleton("a"));
    System.out.println(Collections.singletonMap("a","b"));
 
 }

}</source>

[a]
[a]
{a=b}