1.6 Enhancements in Collection framework

13 March 2021 - 4 mins read time
Tags: Core Java Collections

As a part of 1.6 version, the following two enhancements were introduced in Collection framework:

  1. NavigableSet
  2. NavigableMap

It is the child interface of SortedSet and it defines several methods for navigation purposes.

Methods in NavigableSet interface

floor(e); // Returns highest element which is <= e.
lower(e); // Returns highest element which is < e.
ceiling(e); // Returns highest element which is >= e.
higher(e); // Returns highest element which is > e.
pollFirst(); // Removes and returns the first element.
pollLast(); // Removes and returns the last element.
descendingSet(); // Returns NavigableSet in reverse order.

Demo implementation

import java.util.TreeSet;
public class NavigableSetDemo {
    public static void main(String[] args){
        TreeSet<Integer> treeSet = new TreeSet<Integer>();
        treeSet.add(1000);
        treeSet.add(2000);
        treeSet.add(3000);
        treeSet.add(4000);
        treeSet.add(5000);
        System.out.println(treeSet); // [1000, 2000, 3000, 4000, 5000]
        System.out.println(treeSet.floor(3000)); // 3000
        System.out.println(treeSet.lower(3000)); // 2000
        System.out.println(treeSet.ceiling(3000)); // 3000
        System.out.println(treeSet.higher(3000)); // 4000
        System.out.println(treeSet.pollFirst()); // 1000
        System.out.println(treeSet.pollLast()); // 5000
        System.out.println(treeSet.descendingSet()); // [4000, 3000, 2000]
        System.out.println(treeSet); // [2000, 3000, 4000]
    }
}

It is the child interface of SortedMap. It defines several methods for navigation purposes.

Methods in NavigableMap interface

floorKey(e); // Returns highest key which is <= e.
lowerKey(e); // Returns highest key which is < e.
ceilingKey(e); // Returns highest key which is >= e.
higherKey(e); // Returns highest key which is > e.
pollFirstEntry(); // Removes and returns the first entry.
pollLastEntry(); // Removes and returns the last entry.
descendingMap(); // Returns NavigableMap in reverse order.

Demo Implementation

import java.util.TreeMap;
public class NavigationMapDemo {
    public static void main(String[] args){
        TreeMap<String, String> treeMap = new TreeMap<String, String>();
        treeMap.put("A", "Apple");
        treeMap.put("B", "Ball");
        treeMap.put("C", "Cat");
        treeMap.put("D", "Dog");
        treeMap.put("E", "Elephant");
        treeMap.put("F", "Fan");
        System.out.println(treeMap);// {A=Apple, B=Ball, C=Cat, D=Dog, E=Elephant, F=Fan}
        System.out.println(treeMap.floorKey("C")); // C
        System.out.println(treeMap.lowerKey("C")); // B
        System.out.println(treeMap.ceilingKey("C")); // C
        System.out.println(treeMap.higherKey("C")); // D
        System.out.println(treeMap.pollFirstEntry()); // A: Apple
        System.out.println(treeMap.pollLastEntry()); // F: Fan
        System.out.println(treeMap.descendingMap()); // {E=Elephant, D=Dog, C=Cat, B=Ball}
        System.out.println(treeMap); // {B=Ball, C=Cat, D=Dog, E=Elephant}
    }
}