NavigableSet and NavigableMap Interface in Java

NavigableSet and NavigableMap Interface in Java |  Java 1.6 Version Enhancement in Collection Framework | As part of the 1.6 version the following 2 concepts were introduced in the collection framework:-

• NavigableSet(I)
• NavigableMap(I)

NavigableSet Interface in Java

• Collection(I) 1.2v
  • Set(I) 1.2v
    • SortedSet(I) 1.2v
      • NavigableSet(I) 1.6v
        • TreeSet 1.2v

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

NavigableSet defines the following methods:-

• floor(e):- It returns the highest element which is <= e.
• lower(e):- It returns highest element which is < e.
• ceiling(e):- It returns lowest elements is which is >= e.
• higher(e):- It returns lowest element which is > e.
• pollFirst():- It removes and returns the first element.
• pollLast():- It removes and returns the last element.
• descendingSet():- It returns NavigableSet in reverse order.

import java.util.TreeSet;

public class Test {
    public static void main(String[] args) {
        TreeSet<Integer> treeSet = new TreeSet<>();
        treeSet.add(1000);
        treeSet.add(1500);
        treeSet.add(2000);
        treeSet.add(2500);
        treeSet.add(3000);
        treeSet.add(4000);
        System.out.println(treeSet);
        // [1000, 1500, 2000, 2500, 3000, 4000]

        System.out.println(treeSet.ceiling(2000)); // 2000
        System.out.println(treeSet.higher(2000)); // 2500
        System.out.println(treeSet.floor(3000)); // 3000
        System.out.println(treeSet.lower(3000)); // // 2500
        System.out.println(treeSet.pollFirst()); // 1000
        System.out.println(treeSet.pollLast()); // 4000

        System.out.println(treeSet); // [1500, 2000, 2500, 3000]
        System.out.println(treeSet.descendingSet()); // [3000, 2500, 2000, 1500]
    }
}

NavigableMap Interface in Java

• Map(I) 1.2v
  • SortedMap(I) 1.2v
    • NavigableMap(I) 1.6v
      • TreeMap 1.2v

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

NavigableMap defines the following methods:-

• floorKey(e)
• lowerKey(e)
• ceilingKey(e)
• higherKey(e)
• pollFirstEntry()
• pollLastEntry()
• descendingMap()

import java.util.TreeMap;

public class Test {
    public static void main(String[] args) {
        TreeMap<String, String> treeMap = new TreeMap<>();
        treeMap.put("B", "Banana");
        treeMap.put("C", "Cat");
        treeMap.put("A", "Apple");
        treeMap.put("D", "Dog");
        treeMap.put("G", "Good");
        System.out.println(treeMap);
        // {A=Apple, B=Banana, C=Cat, D=Dog, G=Good}

        System.out.println(treeMap.ceilingKey("C")); // C
        System.out.println(treeMap.higherKey("E")); // G
        System.out.println(treeMap.floorKey("E")); // D
        System.out.println(treeMap.lowerKey("E")); // D
        System.out.println(treeMap.pollFirstEntry()); // A=Apple
        System.out.println(treeMap.pollLastEntry()); // G=Good

        System.out.println(treeMap); // {B=Banana, C=Cat, D=Dog}
        System.out.println(treeMap.descendingMap()); // {D=Dog, C=Cat, B=Banana}
    }
}

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