Using an instance variable of an object in a different class

Question

I made an object called one using the Shape class, and I called the instance variable x1 for 'one', and set it to int x by doing int x = one.x1; and it works fine. But when I tried to do that in a different class, it doesn't work at all. When I tried to do that in a different class an error message shows up that said "one cannot be resolve to a variable." If anyone know what's wrong, and how to fix this, please let me know. Thank you.

package events;

public class Shape {

int x1;
int x2;
int y1;
int y2;
int width;
int height;

Shape(int x1, int y1, int width, int height) {

    this.x1 = x1;
    this.y1 = y1;
    this.width = width;
    this.height = height;
    this.x2 = x1 + width;
    this.y2 = y1 + height;

}

public static void main(String[] args){

    Shape one = new Shape(4,4,4,4);

    int x = one.x1;

}

}

The codes that doesn't work:

package events;

public class test {

public static void main(String[] args){
    int x = one.x1;

}

}

You've pasted the code that works. You should probably paste the code that doesn't work so we can see what you're trying to do. — Paul Boddington
– Paul Boddington, Commented Mar 31, 2015 at 21:48
Variables in Java aren't global, their visibility scope depends on place they're defined. In your code, one is defined inside main() method and is not accessible nor visible anywhere outside it. — Alex Salauyou
– Alex Salauyou, Commented Mar 31, 2015 at 21:49
So I have to initialize one in the class, make it static too, and when I call it in another class, I have to use Shape.one.x1 to call it. I see. Thank you. — Skillet
– Skillet, Commented Mar 31, 2015 at 21:55

Epicblood · Accepted Answer · 2015-03-31 21:55:05Z

1

You have to set the variables as public public int x1; if you want to access them externally.

However it is good practice to use getters and setters instead:

//things
private int x1;
//more stuff
public int getx1(){
    return x1;
}
public void setX1(int x){
    x1 = x;
}

Edit:

appears I've missed the point of the question, to actually answer it, you cannot access a variable outside of where it is defined. If you want to use one somewhere else, you will have to either create a setter for it, or define it in a broader scope.

If you must, I recommend doing something like i show above, define private Shape one; then set it in main one = new Shape(...) and add a getter for it public Shape getOne(){...}

then in the test class you can call getOne() and access the variables.

edited Mar 31, 2015 at 21:55

answered Mar 31, 2015 at 21:49

Epicblood

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3 Comments

Paul Boddington Over a year ago

The error message was "one cannot be resolve to a variable.", so the problem is with one, not x1.

Alex Salauyou Over a year ago

I believe OP's problem is of using one somewhere outside main() method

Epicblood Over a year ago

ah, completely missed that.

Skillet · Accepted Answer · 2015-03-31 21:56:44Z

1

This one works:

package events;

public class Shape {

int x1;
int x2;
int y1;
int y2;
int width;
int height;
static Shape one = new Shape(4,4,4,4);

Shape(int x1, int y1, int width, int height) {

    this.x1 = x1;
    this.y1 = y1;
    this.width = width;
    this.height = height;
    this.x2 = x1 + width;
    this.y2 = y1 + height;

}

public static void main(String[] args){


    int x = one.x1;

}

}

A different class:

package events;

public class test {

public static void main(String[] args){
    int x = Shape.one.x1;

}

}

answered Mar 31, 2015 at 21:56

Skillet

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