从另一个类访问变量

Question

I am just a newbie in Java. I have this following code snippets:

class Canvas extends JPanel{
    int x=-10,y=-10,z=-10;
    public Canvas() {
    }
    public void setCoordinates(int x,int y, int z){
        this.x=x;
        this.y=y;
        this.z=z;
    }
    public void paintComponent(Graphics g) {
        for(int i=0; i<50 ;i++){
            if(p[i].z==1) g.setColor(Color.red);
            else if (p[i].z==2) g.setColor(Color.green);
            else g.setColor(Color.blue);
            g.fillArc(p[i].x-5,p[i].y-5,10,10,0,360);
        }
    }
}

I have this class, it's a separate class from the one where p belongs.

public class Frame extends JFrame{
      ......
      public static Points[] p = new Points[50];
      ....
}

How can I call the points I have in the class Frame so that I can use it in the class Canvas??

Answer 1

If you declare in this way:

public static Points[] p = new Points[50];

you can do: Frame.p beacuse p is static

Instead if you declare private Points[] p = new Points[50]; you use a getter method in Frame class :

public Point[] getPoints() {
    return this.p;
}

Answer 2

Frame.p ，因为它是static并且名称是p 。

Answer 3

as p is public static you can access it by Frame.p , but this is not nice and elegant way

if you want to do this properly, you will create separate object which holds all your points, you can make it singleton if you want have only one instance. If you create it when your application is created you can pass it to each frame which is using it, or just use static method to access it(will work if you have singleton)

Answer 4

由于p是Frame类的公共静态字段，因此可以使用诸如Frame.p类的类名来访问它

Answer 5

您可以直接访问Frame.p因为该字段是公共静态的

Answer 6

You can use public and static fields of one class in other class with its class-name.

Since in your class Frame the field p is public static , so You can use field p as Frame.p in class Canves .

More about static fields : Static fields