Java : Collection Framework : Collections(newSetFromMap)

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CollectionsExample.java

import java.util.Collections;
import java.util.Map;
import java.util.Set;
import java.util.WeakHashMap;

/*
 Method 

 public static <E> Set<E> newSetFromMap(Map<E,Boolean> map)

 Parameters:

 map - the backing map

 Returns:

 the set backed by the map

 */

public class CollectionsExample
{

    public static void main(String[] args)
    {

        Map<String, Boolean> map = new WeakHashMap<String, Boolean>();
        
        System.out.println("Map is: " + map);

        /*
         * Returns a set backed by the specified map. The resulting set displays
         * the same ordering, concurrency, and performance characteristics as
         * the backing map. In essence, this factory method provides a Set
         * implementation corresponding to any Map implementation. There is no
         * need to use this method on a Map implementation that already has a
         * corresponding Set implementation (such as HashMap or TreeMap).
         */
        Set<String> set = Collections.newSetFromMap(map);

        System.out.println("set is: " + set);
        
        set.add("Java");
        set.add("C");
        set.add(".Net");

        System.out.println("Set is: " + set);
        System.out.println("Map is: " + map);

    }
}

Output

Map is: {}
set is: []
Set is: [Java, C, .Net]
Map is: {Java=true, C=true, .Net=true}

To Download CollectionsDemo-newSetFromMap Project Click the below link
https://sites.google.com/site/javaee4321/java-collections/CollectionsDemo-newSetFromMap.zip?attredirects=0&d=1

See also:

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