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TreeMap in java


TreeMap:

TreeMap extends AbstractMap class and implements the NavigableMap  interface. It contains the elements in key-value pair form. It maintains ascending order for its elements. It not allowed duplicate key.

Note: A TreeMap can have only one null key but can have multiple null values.

TreeMap example:

TreeMapTest.java

import java.util.Iterator;
import java.util.Map;
import java.util.Set;
import java.util.TreeMap;
 
/**
 * This class is used to show the TreeMap functionality.
 * @author codesjava
 */
public class TreeMapTest {
	public static void main(String args[]){
		//Create TreeMap object.
		Map treeMap = new TreeMap();
 
		//Add objects to the TreeMap.
		treeMap.put(4, "Roxy");
		treeMap.put(2, "Sunil");
		treeMap.put(5, "Sandy");
		treeMap.put(1, "Munish");
		treeMap.put(3, "Pardeep");
 
		//Print the TreeMap object.
		System.out.println("TreeMap elements:");
		System.out.println(treeMap);
 
		//Get iterator
		Set set=treeMap.entrySet();  
		Iterator iterator=set.iterator();  
 
		//Print the TreeMap elements using iterator.
		System.out.println("TreeMap elements using iterator:");
		while(iterator.hasNext()){
		   Map.Entry mapEntry=(Map.Entry)iterator.next();  
		   System.out.println("Key: " + mapEntry.getKey() + ", " +
		   		"Value: " + mapEntry.getValue());  
		}  
	}
}

Output:

TreeMap elements:
{1=Munish, 2=Sunil, 3=Pardeep, 4=Roxy, 5=Sandy}
TreeMap elements using iterator:
Key: 1, Value: Munish
Key: 2, Value: Sunil
Key: 3, Value: Pardeep
Key: 4, Value: Roxy
Key: 5, Value: Sandy

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