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}