Get Head Map from TreeMap in Java

Java 8Object Oriented ProgrammingProgramming

Use the headMap() method in Java to get ahead map. It returns a view of the portion of this map whose keys are less than or equal to.

Let’s say you need to get the portion of the map above the set map (and not inclusive of it). For that, use the headMap() method like this −

m.headMap(4)

If you want the value 4 to be included as well, then set it as true −

m.headMap(4, true)

The following is an example to get Head Map from Java TreeMap −

Example

 Live Demo

import java.util.*;
public class Demo {
   public static void main(String args[]) {
      TreeMap<Integer,String> m = new TreeMap<Integer,String>();
      m.put(1,"PHP");
      m.put(2,"jQuery");
      m.put(3,"JavaScript");
      m.put(4,"Ruby");
      m.put(5,"Java");
      m.put(6,"AngularJS");
      m.put(7,"ExpressJS");
      System.out.println("TreeMap Elements...\n"+m);
      System.out.println("\nHead Map has = "+m.headMap(4));
   }
}

Output

TreeMap Elements...
{1=PHP, 2=jQuery, 3=JavaScript, 4=Ruby, 5=Java, 6=AngularJS, 7=ExpressJS}
Head Map has = {1=PHP, 2=jQuery, 3=JavaScript}
raja
Published on 30-Jan-2019 07:50:17
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