# Java Program to Return -1 if Point is on Left and 1 if Point is on Right

In the previous article, we have discussed about Java Program to Calculate the Length of Hypotenuse

In this article we are going to see how to return -1 if point is on Left and 1 if point is on Right by using Java programming language.

## Java Program to Return -1 if Point is on Left and 1 if Point is on Right

Before Jumping into the program directly let’s see how to  Return -1 if Point is on Left and 1 if Point is on Right.

Suppose there is a line segment SE, Where the starting point is S having coordinates sx, sy ,Ending point  E is having coordinates ex, ey and we draw a point p having coordinates px, py

So if the point P lies in between SE then returns 0

If the point P lies in left side of SE then returns -1

If the point P lies in right side of SE then returns 1

We can check the point using distance formula

SP = √(PX-SX)2 + (PY-SY)2

EP = √(PX-EX)2 + (PY-EY)2

SE = √(SX-EX)2 + (SY-EY)2

Now,

If SP + EP = SE, Then point lies in between SE (returns 0)

If SP + EP != SE, && SP < EP Then point lies in left side of SE  (returns -1)

If SP + EP != SE, && SP > EP Then point lies in right side of SE  (returns 1)

Example:

Sx = 0, sy = 0 , ex = 0 , ey = 5, px = 0, py = (-9)

SP = 9

EP = 14

SE = 5

Since SP < EP, hence point P lies in left side of SE  & returns -1

Let’s see different ways to return -1 if point is on Left and 1 if point is on Right.

### Method-1: Java Program to Return -1 if Point is on Left and 1 if Point is on Right By Using Static Input Value

Approach:

• Declare an double variable say ‘sx’ and assign the value to it, which holds the x coordinate of point S
• Declare an double variable say ‘sy’ and assign the value to it, which holds the y coordinate of point S
• Declare an double variable say ‘px’ and assign the value to it, which holds the x coordinate of point P
• Declare an double variable say ‘py’ and assign the value to it, which holds the y coordinate of point P
• Declare an double variable say ‘ex’ and assign the value to it, which holds the x coordinate of point E
• Declare an double variable say ‘ey’ and assign the value to it, which holds the y coordinate of point E
• Find the distance of SP, EP, SE using the distance formula
• SP = √(PX-SX)2 + (PY-SY)2
• EP = √(PX-EX)2 + (PY-EY)2
• SE = √(SX-EX)2 + (SY-EY)2
• Print the result.

Program:

public class Main
{
public static int check(float sx,float sy,float ex,float ey,float px,float py)
{

double sp = Math.sqrt(Math.pow(px-sx,2)+Math.pow(py-sy,2));
double ep = Math.sqrt(Math.pow(px-ex,2)+Math.pow(py-ey,2));
double se = Math.sqrt(Math.pow(ex-sx,2)+Math.pow(ey-sy,2));
if (sp+ep == se)
return 0;
else if (sp+ep != se && sp < ep)
return -1;
else
return 1;
}
public static void main(String[] args)
{
float sx = 0;
float sy = 0;
float ex = 0;
float ey = 5;
float px = 0;
float py = -9;
int result = check(sx,sy,ex,ey,px,py);
System.out.println(result);
}
}

Output:

-1

### Method-2: Java Program to Return -1 if Point is on Left and 1 if Point is on Right By Using User Input Value

Approach:

• Declare an double variable say ‘sx’ which holds the x coordinate of point S
• Declare an double variable say ‘sy’ which holds the y coordinate of point S
• Declare an double variable say ‘px’ which holds the x coordinate of point P
• Declare an double variable say ‘py’ which holds the y coordinate of point P
• Declare an double variable say ‘ex’ which holds the x coordinate of point E
• Declare an double variable say ‘ey’ which holds the y coordinate of point E
• Then we will take the value of “sx”, “sy”, “px”, “py”, “ex”, “ey” as user input using scanner class.
• Find the distance of SP, EP, SE using the distance formula
• SP = √(PX-SX)2 + (PY-SY)2
• EP = √(PX-EX)2 + (PY-EY)2
• SE = √(SX-EX)2 + (SY-EY)2
• Print the result.

Program:

import java.util.*;
public class Main
{
public static int check(double sx,double sy,double ex,double ey,double px,double py)
{
// formula to find distance of SP, EP, SE
double sp = Math.sqrt(Math.pow(px-sx,2)+Math.pow(py-sy,2));
double ep = Math.sqrt(Math.pow(px-ex,2)+Math.pow(py-ey,2));
double se = Math.sqrt(Math.pow(ex-sx,2)+Math.pow(ey-sy,2));
// Checking conditions
if (sp+ep == se)
return 0;
else if (sp+ep != se && sp < ep)
return -1;
else
return 1;
}
public static void main(String[] args)
{

Scanner s = new Scanner(System.in);
System.out.println("Enter the x coordinate of starting point S");
double sx = s.nextDouble();
System.out.println("Enter the y coordinate of starting point S");
double sy = s.nextDouble();
System.out.println("Enter the x coordinate of ending point E");
double ex = s.nextDouble();
System.out.println("Enter the y coordinate of ending point E");
double ey = s.nextDouble();
System.out.println("Enter the x coordinate of point P");
double px = s.nextDouble();
System.out.println("Enter the y coordinate of point P");
double py = s.nextDouble();
int result = check(sx,sy,ex,ey,px,py);
System.out.println("----------------------------------------------");
System.out.println(result);
}
}

Output:

Enter the x coordinate of starting point S
0
Enter the y coordinate of starting point S
0
Enter the x coordinate of ending point E
0
Enter the y coordinate of ending point E
5
Enter the x coordinate of point P
0
Enter the y coordinate of point P
3
----------------------------------------------
0

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