Java - Collection Framework Navigable Set

Introduction

A navigable set is a specialized type sorted set.

It provides four methods, lower(), floor(), higher(), and ceiling(), that are used to search for an element based on search criteria.

TreeSet class implements the NavigableSet interface.

The following code uses navigable sets.

It uses integers as the elements of the NavigableSet.

Demo

import java.util.NavigableSet;
import java.util.TreeSet;

public class Main {
  public static void main(String[] args) {
    // Create a navigable set and add some integers
    NavigableSet<Integer> ns = new TreeSet<>();
    ns.add(1);/*from  w w  w  . j  a va2  s  .c  o m*/
    ns.add(2);
    ns.add(3);
    ns.add(4);
    ns.add(5);

    // Get a reverse view of the navigable set
    NavigableSet reverseNs = ns.descendingSet();

    // Print the normal and reverse views
    System.out.println("Normal View of the Set: " + ns);
    System.out.println("Reverse view of the set: " + reverseNs);

    // Get and print a subset of the navigable set
    System.out.println("\nGetting subset of the set");

    NavigableSet threeOrMore = ns.tailSet(3, true);
    System.out.println("3 or more: " + threeOrMore);

    // Search the navigable set
    System.out.println();
    System.out.println("Searching through the set");

    System.out.println("lower(3): " + ns.lower(3));
    System.out.println("floor(3): " + ns.floor(3));
    System.out.println("higher(3): " + ns.higher(3));
    System.out.println("ceiling(3): " + ns.ceiling(3));

    // Poll the navigable set
    System.out.println();
    System.out.println("Polling elements from the set");

    // Poll elements one by one and look at the set
    System.out.println("pollFirst(): " + ns.pollFirst());
    System.out.println("Navigable Set: " + ns);

    System.out.println("pollLast(): " + ns.pollLast());
    System.out.println("Navigable Set: " + ns);

    System.out.println("pollFirst(): " + ns.pollFirst());
    System.out.println("Navigable Set: " + ns);

    System.out.println("pollFirst(): " + ns.pollFirst());
    System.out.println("Navigable Set: " + ns);

    System.out.println("pollFirst(): " + ns.pollFirst());
    System.out.println("Navigable Set: " + ns);

    // Since the set is empty, polling will return null
    System.out.println("pollFirst(): " + ns.pollFirst());
    System.out.println("pollLast(): " + ns.pollLast());
  }
}

Result