# Java: 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. A triangle is 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: **

**Java Code Editor:**

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## Java: Tips of the Day

**DropElements**

Removes elements in an array until the passed function returns true. Returns the remaining elements in the array.

Loop through the array, using Arrays.copyOfRange() to drop the first element of the array until the returned value from the function is true. Returns the remaining elements.

public static int[] dropElements(int[] elements, IntPredicate condition) { while (elements.length > 0 && !condition.test(elements[0])) { elements = Arrays.copyOfRange(elements, 1, elements.length); } return elements; }

Ref: https://bit.ly/37YWqzD

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