class practice

[Jhon Schmidt]

[URL removed. Lines too long. See response below. (Knute)]

The exercises website is above. below is question 3 and 4.

Object class(MyPoint)- http://pastebin.com/VcvdXzFF
Class which object is a variable- http://pastebin.com/TdebBt9X
Main method http://pastebin.com/tRS195ur

I need help with the last two methods of question 3.
and I don't know how to do 3 methods in question 4: getCenterX(),GetCenterY(),getCenterXY().

thanks a lot for all who will help me.

[Knute Snortum]

Welcome to the Ranch!

This is the preferred way to post a question with code.

Actual URL to questions, not copied from Google results page: http://www.ntu.edu.sg/home/ehchua/programming/java/J3f_OOPExercises.html

Code pasted with code tags.

public class MyPoint {
	private int x = 0;
	private int y = 0;
	
	public MyPoint(){}
	
	public MyPoint(int x, int y){
		this.x = x;
		this.y = y;
	}

	public int getX() {
		return x;
	}

	public void setX(int x) {
		this.x = x;
	}

	public int getY() {
		return y;
	}

	public void setY(int y) {
		this.y = y;
	}
	
	public void setXY(int x, int y){
		this.x = x;
		this.y = y;
	}

	public String toString() {
		return "(" + x + "," + y + ")";
	}
		
}

What are your specific questions?

[Jhon Schmidt]

these are the questions for the class you wrote (MyPoint), I need to add these two methods
1.A method called distance(int x, int y) that returns the distance from this point to another point at the given (x, y) coordinates.
2.An overloaded distance(MyPoint another) that returns the distance from this point to the given MyPoint instance another.

[Sachin Tripathi]

For 1)add a method:
double distance(int x,int y)
{
//calculate distance between this and
//method parameter,return thedistance
}
2)add another method:
double distance(MyPoint m)
{
//CALCULATE DISTANCE BETWEEN
//this and and instance variable of m
//reference
//return the distance
}



Be careful while invoking distance method with reference of MyPoint as its argument.

[Jhon Schmidt]

Sachin Tripathi wrote:For 1)add a method:
double distance(int x,int y)
{
//calculate distance between this and
//method parameter,return thedistance
}
2)add another method:
double distance(MyPoint m)
{
//CALCULATE DISTANCE BETWEEN
//this and and instance variable of m
//reference
//return the distance
}




Yeah man I understand what you wrote but I really need the body of the method, I dont know how to do that.

[Knute Snortum]

Yeah man I understand what you wrote but I really need the body of the method, I dont know how to do that.

JavaRanch is NotACodeMill (← that's a link) so we don't provide complete solutions, but we can help you find that answer yourself. ShowSomeEffort by writing as much of the method as you can, or asking a specific question.

[Knute Snortum]

I did this search:

formula for distance between two points

And found several sites that give you a generic distance formula. You can use that in your double distance(int x,int y) method.

[Sachin Tripathi]

Try it yourself, and believe me you'll get it easily
And even if you fail( which you are not going to) post your specific question here,we are good people (atleast me and knute surely are )we will help you

[Jhon Schmidt]

well, this is what I wrote.

public double distance(int x, int y) {   
		   int xDiff = this.x – x;
		   int yDiff = this.y – y;
		   return Math.sqrt(xDiff*xDiff + yDiff*yDiff);
		}

and here is what I wrote in the main method:

MyPoint p4 = new MyPoint(5,6);
System.out.println(p4.distance(2, 2));

this is the error:
Exception in thread "main" java.lang.Error: Unresolved compilation problems:
The target type of this expression must be a functional interface
Syntax error on token "Invalid Character", :: expected
The target type of this expression must be a functional interface
Syntax error on token "Invalid Character", :: expected

at MyPoint.distance(MyPoint.java:39)
at main.main(main.java:108)

What should I do? what's the problem?
It looks like it has a problem with these two lines:

int xDiff = this.x – x;
int yDiff = this.y – y;

[Knute Snortum]

The code you posted looks good. Could you post all of the code and maybe we can figure out what's happening.

[Sachin Tripathi]

I can't see any problem with what you did
It is compiling without error and giving accurate result
You might be doing wrong at someother places(recheck the signature of your main method)