如果我设置一个具有从另一个类定义的2个参数的类方法，我如何获得在另一个类上定义的值？

Question

say I declared a Camera class

public class Camera {
}

then I created another class

public int compare (Camera camOne, Camera camTwo) {
}

If I set the value of camOne.price , where price is a defined value in the Camera class, how can I retrieve the value?

Answer 1

You could make it public:

public int var

Or create getter and setter methods:

public static int getVar ()
{
    return var;
}

Answer 2

Most usually you would do one of two options:

1. Least preferred:

public class Camera {
    public float price;
}

public class CameraComparer {
    public float compare (Camera camOne, Camera camTwo) {
        // do something; e.g. return difference
        return camOne.price - camTwo.price;
    }
}

2. More preferred/Standard:

public class Camera {
    private float price;

    public float getPrice() {
        return price;
    } 
}

public class CameraComparer {
    public float compare (Camera camOne, Camera camTwo) {
        return camOne.getPrice() - camTwo.getPrice();
    }
}

Answer 3

What are you trying to accomplish?

Is there a reason why you would prefer not to use a private access modifier, and a getter method. I would be concerned to make it public just because of ease of use, as it could cause issues down the road.

Based on the comments I have read it seems like you are trying to make a compare method, which is fairly common. Maybe another approach could be implementing the Comparable interface , and this would force you to implement the compareTo method.

See the following code for an example:

package com.grade;

import java.util.Comparator;

public class Grade implements Comparable {

    private double percentage;

    public double getPercentage() {
        return percentage;
    }

    public void setPercentage(double percentage) {
        this.percentage = percentage;
    }

    @Override
    public int compareTo(Object o1) {
        if (o1 instanceof Grade) {
            Grade grade1 = (Grade) o1;
            if (this.getPercentage() > grade1.getPercentage()) {
                return 1;
            } else if (this.getPercentage() < grade1.getPercentage()) {
                return -1;
            } else {
                return 0;
            }
        }
        return -1;
    }

    @Override
    public boolean equals(Object obj1) {
        if (obj1 instanceof Grade) {
            Grade grade1 = (Grade) obj1;
            if (this.getPercentage() == grade1.getPercentage()) {
                return true;
            } else {
                return false;
            }
        }
        return false;
    }

    public static void main(String args[]) {
        Grade chem = new Grade();
        chem.setPercentage(92.50);
        Grade astro = new Grade();
        astro.setPercentage(40.12);

        System.out.println(chem.compareTo(astro));
    }
}