Iterate/ loop TreeMap collection of String Objects before & after java8 (example)

1. What is TreeMap collection in java?

1. Given a TreeMap  collection containing key value pairs.
   • TreeeMap is Red-Black tree based NavigableMap implementation.
2. The map is sorted according to the natural ordering of its keys, or by a Comparator provided at map creation time
3. Guaranteed time complexity log(n)  for the containsKey, get, put and remove operations.
4. Iterate or loop through the TreeMap using following methods.
   1. Iterate TreeMap collection of TreeMap<Integer,String> using entrySet iterator
   2. Iterate TreeMap collection of TreeMap<Integer,String> using forEach (java8)
5. Once we accomplished the iteration process, the keys will be printed in sorted order.

2. Loop /iterate TreeMap collection of String objects in before & after java8

package org.learn.collection.map.tmap;

import java.util.Map;
import java.util.Map.Entry;
import java.util.TreeMap;

public class DemoTreeMap {

	public static void main(String[] args) {
		Map<Integer, String> mapVehicleNoAndOwner = new TreeMap<>();

		mapVehicleNoAndOwner.put(9000, "Federer");
		mapVehicleNoAndOwner.put(4000, "Bradman");
		mapVehicleNoAndOwner.put(7000, "Jordan");
		mapVehicleNoAndOwner.put(2000, "Woods");
		mapVehicleNoAndOwner.put(5000, "Ali");
		
		System.out.println("Method 1 - Iterate TreeMap: ");
		demoIterateTreeMap(mapVehicleNoAndOwner);
		
		System.out.println("\nMethod 2 - Iterate TreeMap using java 8: ");
		demoIterateTreeMapJava8(mapVehicleNoAndOwner);
	}

	private static void demoIterateTreeMap(Map<Integer, String> mapVehicleNoAndOwner ) {
		for (Entry<Integer, String> entry : mapVehicleNoAndOwner .entrySet()) {
			Integer vehicleNumber = entry.getKey();
			String owner = entry.getValue();
			System.out.println("Key:" + vehicleNumber + ", Value:" + owner);
		}
	}

	private static void demoIterateTreeMapJava8(Map<Integer, String> mapVehicleNoAndOwner) {
		mapVehicleNoAndOwner.forEach((key, value) -> {
			System.out.println("Key:" + key + ", Value:" + value);
		});
	}
}

3. Loop /iterate TreeMap collection of String objects in before & after java8

Method 1 - Iterate TreeMap: 
Key:2000, Value:Woods
Key:4000, Value:Bradman
Key:5000, Value:Ali
Key:7000, Value:Jordan
Key:9000, Value:Federer

Method 2 - Iterate TreeMap using java 8: 
Key:2000, Value:Woods
Key:4000, Value:Bradman
Key:5000, Value:Ali
Key:7000, Value:Jordan
Key:9000, Value:Federer