Friday, 30 January 2015

Java : Collection Framework : TreeMap (Key and value)

TreeMapExample.java
```import java.util.Set;
import java.util.TreeMap;

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

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

treeMap.put(1, "Cat");
treeMap.put(2, "Dog");
treeMap.put(4, "Apple");
treeMap.put(3, "Ball");

System.out.println("treeMap : " + treeMap + "\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
*/
Set<Integer> set = treeMap.keySet();

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

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

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

}

}
}
```
Output
```treeMap : {1=Cat, 2=Dog, 3=Ball, 4=Apple}

set : [1, 2, 3, 4]

-----------------------
Key | value
-----------------------
1   |  Cat
2   |  Dog
3   |  Ball
4   |  Apple
```

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