w3resource

Java Exercises: Check if a point (x, y) is in a triangle or not

Java Basic: Exercise-219 with Solution

Write a Java program to check if a point (x, y) is in a triangle or not. There is a triangle formed by three points.

Input:
x1,y1,x2,y2,x3,y3,xp,yp separated by a single space.

Sample Solution:

Java Code:

import java.util.*;
public class Main { 
    private double outer_product(double x, double y, double x1, double y1, double x2, double y2){
        x1 = x1 - x;
        y1 = y1 - y;
        x2 = x2 - x;
        y2 = y2 - y;
        double s = x1 * y2 - y1 * x2;
        return s;
    } 
    public void point(){
        Scanner sc = new Scanner(System.in);
            double [] x = new double[3];
            double [] y = new double[3];
			System.out.println("Input (x1, y1)");            
                x[0] = sc.nextDouble();
                y[0] = sc.nextDouble();
			System.out.println("Input (x2, y2)");            
                x[1] = sc.nextDouble();
                y[1] = sc.nextDouble();
			System.out.println("Input (x3, y3)");            
                x[2] = sc.nextDouble();
                y[2] = sc.nextDouble();
			System.out.println("Input (xp, yp)");            
                           
            double xp = sc.nextDouble();
            double yp = sc.nextDouble();
            boolean [] ans = new boolean[3];
            for(int i=0; i < 3; i++){
                ans[i] = outer_product(xp, yp, x[i], y[i], x[(i+1)%3], y[(i+1)%3]) > 0.0;
            }
            if(ans[0] == ans[1] && ans[1] == ans[2]){
                
            }
            else{
                System.out.println("The point is outside the triangle.");
            }
      }
    public static void main(String[] args) {
        Main obj = new Main();
        obj.point();
    }
}

Sample Output: 

Input (x1, y1)
2
6
Input (x2, y2)
3
5
Input (x3, y3)
4
6
Input (xp, yp)
5
6
The point is outside the triangle.

Flowchart:

Flowchart: Java exercises: Check if a point (x, y) is in a triangle or not.

Java Code Editor:

Contribute your code and comments through Disqus.

Previous: Write a Java program to print the number of prime numbers which are less than or equal to a given integer.
Next: Write a Java program to compute and print sum of two given integers (more than or equal to zero). If given integers or the sum have more than 80 digits, print "overflow".

What is the difficulty level of this exercise?



Java: Tips of the Day

Parsing dates:

import java.io.*;
import java.util.*;
import java.text.*;

String s = "2001/09/23 14:39";

SimpleDateFormat formatter = new SimpleDateFormat ("yyyy/MM/dd H:mm");
Date d = formatter.parse(s, new ParsePosition(0));