Java Exercises: Merge all overlapping Intervals from a given a collection of intervals

Java Basic: Exercise-140 with Solution

Write a Java program to merge all overlapping Intervals from a given a collection of intervals.

Sample Solution:

Java Code:

#// Source: https://bit.ly/2PjMfds
import java.util.*;

public class Solution
    public static void main (String[] args) throws java.lang.Exception
        ArrayList<Interval> x = new ArrayList<>();

        x.add(new Interval(1, 3));
        x.add(new Interval(2, 6));
        x.add(new Interval(8, 10));
        x.add(new Interval(15, 18));
        x.add(new Interval(17, 20));

        x = merge(x);

        for(Interval i : x)
            System.out.println(i.getStart() + " " + i.getEnd());

    public static ArrayList<Interval> merge(ArrayList<Interval> intervals) {

        if(intervals.size() == 0 || intervals.size() == 1)
            return intervals;

        Collections.sort(intervals, new IntervalComparator());

        Interval first = intervals.get(0);
        int start = first.getStart();
        int end = first.getEnd();

        ArrayList<Interval> result = new ArrayList<Interval>();

        for (int i = 1; i < intervals.size(); i++) {
            Interval current = intervals.get(i);
            if (current.getStart() <= end) {
                end = Math.max(current.getEnd(), end);
            } else {
                result.add(new Interval(start, end));
                start = current.getStart();
                end = current.getEnd();

        result.add(new Interval(start, end));
        return result;

class Interval 
    private int start;
    private int end;

    Interval() {
        start = 0;
        end = 0;

    Interval(int s, int e) 
        start = s;
        end = e;

    public int getStart() {
        return start;

    public int getEnd() {
        return end;

class IntervalComparator implements Comparator<Interval>
    public int compare(Interval i1, Interval i2)
        return i1.getStart() - i2.getStart();

Sample Output:

1 6
8 10
15 20


Flowchart: Java exercises: Merge all overlapping Intervals from a given a collection of intervals.

Java Code Editor:

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Java: Tips of the Day


Counts the occurrences of a value in an array.

Use Arrays.stream().filter().count() to count total number of values that equals the specified value.

public static long countOccurrences(int[] numbers, int value) {
    return Arrays.stream(numbers)
            .filter(number -> number == value)

Ref: https://bit.ly/3kCAgLb