Collection singleton
In this chapter you will learn:
Create singleton Collection
static<T> Set<T> singleton(T o)Returns an immutable set containing only the specified object.static<T> List<T> singletonList(T o)Returns an immutable list containing only the specified object.static<K,V> Map<K,V>singletonMap(K key, V value) Returns an immutable map, mapping only the specified key to the specified value.
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;
/* j av a2 s. co m*/
public class MainClass {
public static void main(String args[]) {
String init[] = { "One", "Two", "Three", "One", "Two", "Three" };
List list1 = new ArrayList(Arrays.asList(init));
List list2 = new ArrayList(Arrays.asList(init));
list1.remove("One");
System.out.println(list1);
list2.removeAll(Collections.singleton("One"));
System.out.println(list2);
}
}
The output:
Singleton from array
import java.util.Collections;
//from j av a2 s . c om
public class Main {
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"));
}
}
The output:
Next chapter...
What you will learn in the next chapter: