JAVA EE: Java : Collection Framework : TreeMap (tailMap)

Wednesday 4 February 2015

Java : Collection Framework : TreeMap (tailMap)

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TreeMapExample.java

import java.util.Set;
import java.util.SortedMap;
import java.util.TreeMap;

/*
 * Example of tailMap(K fromKey) method.
 */
public class TreeMapExample
{
    public static void main( String[] args )
    {

        TreeMap<Integer, String> treeMap = new TreeMap<Integer, String>();

        treeMap.put(10, "Cat");
        treeMap.put(50, "Dog");
        treeMap.put(30, "Apple");
        treeMap.put(40, "Ball");
        treeMap.put(20, "Eagle");

        System.out.println("treeMap : " + treeMap + "\n");

        /*
         * Returns a view of the portion of this map whose keys are greater than
         * or equal to fromKey. The returned map is backed by this map, so
         * changes in the returned map are reflected in this map, and
         * vice-versa. The returned map supports all optional map operations
         * that this map supports.
         * 
         * Equivalent to tailMap(fromKey, true).
         */
        SortedMap<Integer, String> sortedMap = treeMap.tailMap(30);

        System.out.println("sortedMap : " + sortedMap + "\n");

        Set<Integer> set = sortedMap.keySet();

        System.out.println("set : " + set + "\n");

        System.out.println("-----------------------");
        System.out.println("Key" + " | " + "value");
        System.out.println("-----------------------");

        for( Integer key : set )
        {
            String value = sortedMap.get(key);
            System.out.println(key + "   |  " + value);
        }

    }
}

Output

treeMap : {10=Cat, 20=Eagle, 30=Apple, 40=Ball, 50=Dog}

sortedMap : {30=Apple, 40=Ball, 50=Dog}

set : [30, 40, 50]

-----------------------
Key | value
-----------------------
30   |  Apple
40   |  Ball
50   |  Dog