Java TreeSet lower() Method

---

---

Description

The Java TreeSet lower(E e) method is used to return the greatest element in this set strictly less than the given element, or null if there is no such element.

Declaration

Following is the declaration for java.util.TreeSet.lower() method.

public E lower(E e)

Parameters

e − This is the value to match.

Return Value

The method call returns the greatest element less than e, or null if there is no such element.

Exception

• ClassCastException − This exception is thrown if the specified element cannot be compared with the elements currently in the set.

• NullPointerException − This exception is thrown if the specified element is null and this set uses natural ordering, or its comparator does not permit null elements.

Getting Greatest Elememt Less than Given Element of a TreeSet of Integer Example

The following example shows the usage of Java TreeSet lower() method to get the greatest element in this set strictly less than the given element in the treeset. We've created a TreeSet object of Integer. Then few entries are added using add() method and related value is printed using lower() method.

package com.tutorialspoint;

import java.util.TreeSet;

public class TreeSetDemo {
   public static void main(String[] args) {

      // creating a TreeSet 
      TreeSet<Integer> treeset = new TreeSet<>();

      // adding in the tree set
      treeset.add(12);
      treeset.add(11);
      treeset.add(16);
      treeset.add(15);

      // getting the lower value for 13
      System.out.println("Lower value of 13: "+treeset.lower(13));   
   }       
}

Output

Let us compile and run the above program, this will produce the following result.

Lower value of 13: 15 

Getting Greatest Elememt Less than Given Element of a TreeSet of String Example

The following example shows the usage of Java TreeSet lower() method to get the greatest element in this set strictly less than the given element in the treeset. We've created a TreeSet object of String. Then few entries are added using add() method and related value is printed using lower() method.

package com.tutorialspoint;

import java.util.TreeSet;

public class TreeSetDemo {
   public static void main(String[] args) {

      // creating a TreeSet 
      TreeSet<String> treeset = new TreeSet<>();

      // adding in the tree set
      treeset.add("F");
      treeset.add("B");
      treeset.add("E");
      treeset.add("G");

      // getting the lower value for C
      System.out.println("Lower value of C: "+treeset.lower("C"));   
   }       
}

Output

Let us compile and run the above program, this will produce the following result.

Lower value of C: B

Getting Greatest Elememt Less than Given Element of a TreeSet of Object Example

The following example shows the usage of Java TreeSet lower() method to get the greatest element in this set strictly less than the given element in the treeset. We've created a TreeSet object of Students. Then few entries are added using add() method and related value is printed using lower() method.

package com.tutorialspoint;

import java.util.TreeSet;

public class TreeSetDemo {
   public static void main(String[] args) {

      // creating a TreeSet 
      TreeSet<Student> treeset = new TreeSet<>();

      // adding in the tree set
      treeset.add(new Student(1, "Robert"));
      treeset.add(new Student(3, "Adam"));
	  treeset.add(new Student(2, "Julie"));
      treeset.add(new Student(4, "Julia"));

      // getting the lower value for Adam
      System.out.println("Lower value of Adam: "+treeset.lower(new Student(3, "Adam")));   
   }       
}
class Student implements Comparable<Student> {
   int rollNo;
   String name;

   Student(int rollNo, String name){
      this.rollNo = rollNo;
      this.name = name;
   }

   @Override
   public String toString() {
      return "[ " + this.rollNo + ", " + this.name + " ]";
   }
   
   @Override
   public boolean equals(Object obj) {
      Student s = (Student)obj;
      return this.rollNo == s.rollNo && this.name.equalsIgnoreCase(s.name);
   }

   @Override
   public int compareTo(Student student) {
      return this.rollNo - student.rollNo;
   }
}

Output

Let us compile and run the above program, this will produce the following result.

Lower value of Adam: [ 2, Julie ]