Program: How to get all keys from TreeMap?

Below example shows how to get all keys from the given TreeMap. By using keySet() method, you can get all key entries as a Set object.

package com.java2novice.treemap;

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

public class MyTreeMapKeys {

	public static void main(String a[]){
		TreeMap<String, String> hm = new TreeMap<String, String>();
		//add key-value pair to TreeMap
		hm.put("first", "FIRST INSERTED");
		hm.put("second", "SECOND INSERTED");
		hm.put("third","THIRD INSERTED");
		System.out.println(hm);
		Set<String> keys = hm.keySet();
		for(String key: keys){
			System.out.println(key);
		}
	}
}

{first=FIRST INSERTED, second=SECOND INSERTED, third=THIRD INSERTED}
first
second
third