Java TreeSet - lower() Method

The java.util.TreeSet.lower() method returns the greatest element in this set strictly less than the given element, or null if there is no such element.

Syntax

public E lower(E e)

Here, E is the type of element maintained by the container.

Parameters

Return Value

Returns the greatest element less than e, or null if there is no such element.

Exception

• Throws ClassCastException, if the specified element cannot be compared with the elements currently in the set.
• Throws NullPointerException, if the specified element is null and this set uses natural ordering, or its comparator does not permit null elements.

Example:

In the example below, the java.util.TreeSet.lower() method returns the greatest element in the given set strictly less than the specified value.

import java.util.*;

public class MyClass {
  public static void main(String[] args) {
    //creating a treeset
    TreeSet<Integer> MySet = new TreeSet<Integer>();

    //populating the set
    MySet.add(10);
    MySet.add(20);
    MySet.add(30);
    MySet.add(40);

    //printing the set
    System.out.println("MySet contains: " + MySet); 

    //printing the greatest element less than 25
    System.out.println("Greatest Element less than 25: " + MySet.lower(25));

    //printing the greatest element less than 5
    System.out.println("Greatest Element less than 5: " + MySet.lower(5));  
  }
}

The output of the above code will be:

MySet contains: [10, 20, 30, 40]
Greatest Element less than 25: 20
Greatest Element less than 5: null