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.
// 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)); }} |
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.
// 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")); }} |
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)
