JAVA EE: Java : Collection Framework : LinkedHashMap (Key and Value)

Tuesday 27 January 2015

Java : Collection Framework : LinkedHashMap (Key and Value)

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LinkedHashMapExample.java

import java.util.LinkedHashMap;
import java.util.Set;

/*
 * Example of keySet() method.
 */
public class LinkedHashMapExample
{
    public static void main( String[] args )
    {

        LinkedHashMap<Integer, String> linkedHashMap = new LinkedHashMap<Integer, String>();

        linkedHashMap.put(1, "Apple");
        linkedHashMap.put(3, "Cat");
        linkedHashMap.put(2, "Ball");

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

        /*
         * Returns a Set view of the keys contained in this map. The set is
         * backed by the map, so changes to the map are reflected in the set,
         * and vice-versa.
         * 
         * If the map is modified while an iteration over the set is in progress
         * (except through the iterator's own remove operation), the results of
         * the iteration are undefined. The set supports element removal, which
         * removes the corresponding mapping from the map, via the
         * Iterator.remove, Set.remove, removeAll, retainAll, and clear
         * operations. It does not support the add or addAll operations.
         */
        Set<Integer> set = linkedHashMap.keySet();

        System.out.println("set : "+set + "\n");    
        
        System.out.println("-----------------------");
        System.out.println("Key" +" | " + "value");
        System.out.println("-----------------------");

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

Output

LinkedHashMap : {1=Apple, 3=Cat, 2=Ball}

set : [1, 3, 2]

-----------------------
Key | value
-----------------------
1   |  Apple
3   |  Cat
2   |  Ball