NavigableSet subSet() method in Java

Last Updated : 29 Sep, 2018

The headSet() method of NavigableSet interface in Java is used to return a view of the portion of this set whose elements range from fromElement to toElement.

If fromElement and toElement are equal, the returned set is empty unless fromInclusive and toInclusive are both true.
The returned set is backed by this set, so changes in the returned set are reflected in this set, and vice-versa.
The returned set supports all optional set operations that this set supports.

Note: The returned set will throw an IllegalArgumentException on an attempt to insert an element outside its range. Syntax:

NavigableSet<E> subSet( E fromElement,
                       boolean fromInclusive,
                       E toElement,
                       boolean toInclusive);

Where, E is the type of elements maintained by this Set container. Parameters: This function accepts 4 parameters as explained below:

fromElement: This is a mandatory parameter and specifies the low end point of the returned set.
fromInclusive: This is an optional parameter and is of boolean type. If this is set to True, then low end point will be included in the returned view otherwise not.
toElement: his is a mandatory parameter and specifies the high end point of the returned set.
toInclusive: This is optional parameter and is of boolean type. If this is set to True, then low end point will be included in the returned view otherwise not.

Return Value: It returns a view of the portion of this set whose elements range from fromElement to toElement. Below programs illustrate the subSet() method in Java: Program 1: NavigableSet with integer elements.

Java

// A Java program to demonstrate
// subSet() method of NavigableSet

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

public class GFG {
    public static void main(String[] args)
    {
        NavigableSet<Integer> ns = new TreeSet<>();
        ns.add(0);
        ns.add(1);
        ns.add(2);
        ns.add(3);
        ns.add(4);
        ns.add(5);
        ns.add(6);

        System.out.println("Map with key-value between the given argument : "
                                                           + ns.subSet(1, 6));

        System.out.println("Map with key-value between the given argument : "
                                                           + ns.subSet(2, 6));
    }
}

Output:

Map with key-value between the given argument : [1, 2, 3, 4, 5]
Map with key-value between the given argument : [2, 3, 4, 5]

Program 2: NavigableSet with string elements.

Java

// A Java program to demonstrate
// subSet() method of NavigableSet

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

public class GFG {
    public static void main(String[] args)
    {
        NavigableSet<String> ns = new TreeSet<>();
        ns.add("A");
        ns.add("B");
        ns.add("C");
        ns.add("D");
        ns.add("E");
        ns.add("F");
        ns.add("G");

        System.out.println("Map with key-value between the given range : " 
                                                   + ns.subSet("B", "G"));
    }
}

Output:

Map with key-value between the given range : [B, C, D, E, F]

Reference: https://docs.oracle.com/javase/10/docs/api/java/util/NavigableSet.html#subSet(E, E)

NavigableSet in Java

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