没有抛出异常消息

时间：2014-09-30 22:04:43

标签： java class exception coordinates

嘿，我有一个点类，可以生成一个点列表。该课程如下

public class Point {

private double x, y;



public Point(double x, double y){

    this.x = x;
    this.y = y;

}//end constructor




public Point() {
    // TODO Auto-generated constructor stub
}

public double getX(){
        return x;
}

public void setX(double x) {
    try{ 
        if (x < 0){
            throw new NegArgumentException();
        }//end if
        else{
            this.x = x;

        }//end else
    }//end try
    catch (NegArgumentException e){
        System.out.println("error");
    }//end catch


}

public double getY() {
    return y;
}

public void setY(double y) {
    try{ 
        if (y < 0){
            throw new NegArgumentException();
        }//end if
        else{
            this.y = y;

        }//end else
    }//end try
    catch (NegArgumentException e){
        System.out.println("error");
    }//end catch

}

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

我还创建了自己的异常类NegArgumentException，以便在生成负点时抛出异常。

public class NegArgumentException extends Exception {


public NegArgumentException(){}

public NegArgumentException(String message){
    super(message);
}

}

我还有另外两个类Rectangle和circle 

public class Rectangle {
private Point upperLeft = new Point();
private Point lowerRight = new Point();


public Rectangle(Point upperLeft, Point lowerRight){
    this.upperLeft = upperLeft;
    this.lowerRight = lowerRight;

}//end constructor

public Point getUpperLeft() {
    return upperLeft;
}

public void setUpperLeft(Point upperLeft) {
    this.upperLeft = upperLeft;
}

public Point getLowerRight() {
    return lowerRight;
}

public void setLowerRight(Point lowerRight) {
    this.lowerRight = lowerRight;
}

public Point getUpperRight(){
    return new Point(getLowerRight().getX(), getUpperLeft().getY());
}

public Point getLowerLeft(){
    return new Point(getUpperLeft().getX(), getLowerRight().getY());
}


public double getArea(){
    return upperLeft.getX()*lowerRight.getY();
}

public String toString(){
    return "r[("+upperLeft.getX() + ","+upperLeft.getY()+"),("+lowerRight.getX()+","+lowerRight.getY()+")]";
}
}

Circle类

public class Circle {
private Point center = new Point();
private double radius;

public Circle(){}

public Circle(Point center, double radius){
    this.center = center;
    this.radius = radius;
}

public Point getCenter() {
    return center;
}

public void setCenter(Point center) {
    this.center = center;
}

public String toString(){
    return "c[("+center.getX()+","+center.getY()+"), "+ radius+"]";
}
}

我的主类为每个对象生成一个随机的点列表。

import java.util.ArrayList;

import java.util.Random;

public class Main {

public static void main(String[] args) {
    //create arraylist for each class
    ArrayList<Point> list = new ArrayList<Point>();
    ArrayList<Rectangle> list1 = new ArrayList<Rectangle>();
    ArrayList<Circle> list2 = new ArrayList<Circle>();
    //create random generators
    Random Point = new Random();
    Random myGenerator = new Random();
    int i = 0;
    //go through for loop
    while (i < 100){

        int whichArray = myGenerator.nextInt(4) + 1;
        //print out points for whichever random object
        if (whichArray == 1){
            int pointX = Point.nextInt(41) - 20;
            int pointY = Point.nextInt(41) - 20;
            if (pointX >= 0 && pointY >= 0){
            list.add(new Point(pointX, pointY));
            System.out.println(list.toString());
            list.remove(0);
            i++;
            }
        }//end if
        if (whichArray == 2){
            int pointX = Point.nextInt(41) - 20;
            int pointY = Point.nextInt(41) - 20;
            int pointRandom = Point.nextInt(20) - 20;
            if (pointX >= 0 && pointY >= 0 && pointRandom >= 0){
            list1.add(new Rectangle(new Point(pointX, pointY), new Point(pointX+pointRandom, pointY-pointRandom)));
            System.out.println(list1.toString());
            list1.remove(0);
            i++;
            }

        }//end if
        if (whichArray == 3){
            int pointX = Point.nextInt(41) - 20;
            int pointY = Point.nextInt(41) - 20;
            int radius = Point.nextInt(41) - 20;
            if (pointX >= 0 && pointY >= 0){
            list2.add(new Circle(new Point(pointX, pointY),radius));
            System.out.println(list2.toString());
            list2.remove(0);
            i++;
            }
        }//end if

    }//end while loop

}//end main


}//end class

问题是我没有看到发生异常时显示的任何消息。我知道它有效，因为我没有得到负点坐标。有谁知道为什么没有显示消息？

2 个答案:

答案 0 :(得分：3)

您的代码中有很多不良做法，您应该阅读有关编写干净代码的内容。顺便说一下，没有异常被抛出，因为你的setter永远不会被调用。将构造函数更改为

public Point(double x, double y) {    
    setX(x);
    setY(y);   
}

另外，在创建积分之前，始终确保您的if语句的坐标为正，因此无法实例化无效的Point。

最后，即使它与你的“问题”无关，也不要给变量（你的Random对象）一个以大写字母开头的名字，这对于可读性来说是一个坏习惯。更糟糕的是它也是一个类的名字。如果Point.method()课程method和课程Point中都存在Random，则{{1}}可能会有歧义。

答案 1 :(得分：0)

您正在构造函数中设置Point的值：

list.add(new Point(pointX, pointY));

因此，从不调用setX和setY，因此，如果x和y为负数，则永远无法验证。

尝试这样的事情：

public class Main {
public static void main(String[] args) {
    //create arraylist for each class
    ArrayList<Point> list = new ArrayList<Point>();
    ArrayList<Rectangle> list1 = new ArrayList<Rectangle>();
    ArrayList<Circle> list2 = new ArrayList<Circle>();
    //create random generators
    Random Point = new Random();
    Random myGenerator = new Random();
    int i = 0;
    //go through for loop
    while (i < 100){
    int whichArray = myGenerator.nextInt(4) + 1;
    //print out points for whichever random object
    if (whichArray == 1){
        int pointX = Point.nextInt(41) - 20;
        int pointY = Point.nextInt(41) - 20;
        if (pointX >= 0 && pointY >= 0){
            Point point = new Point();
            point.setX(pointX);
            point.setY(pointY);
            list.add(point);
            System.out.println(list.toString());
            list.remove(0);
            i++;
        }
    }//end if
    if (whichArray == 2){
        int pointX = Point.nextInt(41) - 20;
        int pointY = Point.nextInt(41) - 20;
        int pointRandom = Point.nextInt(20) - 20;
        if (pointX >= 0 && pointY >= 0 && pointRandom >= 0){
            Point point = new Point();
            point.setX(pointX);
            point.setY(pointY);

            Point point2 = new Point();
            point2.setX(pointX+pointRandom);
            point2.setY(pointY-pointRandom);

            list1.add(new Rectangle(point, point2));
            System.out.println(list1.toString());
            list1.remove(0);
            i++;
        }

    }//end if
    if (whichArray == 3){
        int pointX = Point.nextInt(41) - 20;
        int pointY = Point.nextInt(41) - 20;
        int radius = Point.nextInt(41) - 20;
        if (pointX >= 0 && pointY >= 0){
        list2.add(new Circle(new Point(pointX, pointY),radius));
        System.out.println(list2.toString());
        list2.remove(0);
        i++;
        }
    }//end if

}//end while loop

}//end main


}//end class

这样，验证就会发生。

因此，例如，如果您将其更改为：

Point point = new Point();
point.setX(-1);
point.setY(-2);
list.add(point);

它将打印：

error
error
[p(0.0,0.0)]
error
error
[p(0.0,0.0)]
error
error
[p(0.0,0.0)]
[c[(17.0,10.0), 13.0]]
error
error
[p(0.0,0.0)]
error
error
[p(0.0,0.0)]
error
error
[p(0.0,0.0)]
error
error
[p(0.0,0.0)]
[c[(20.0,6.0), 5.0]]
[c[(18.0,1.0), -18.0]]
[c[(18.0,20.0), 10.0]]
error
error
[p(0.0,0.0)]
error
error
[p(0.0,0.0)]
[c[(20.0,19.0), 20.0]]
[c[(20.0,12.0), -14.0]]
[c[(2.0,20.0), 0.0]]
error
error
[p(0.0,0.0)]
[c[(10.0,13.0), 2.0]]
[c[(10.0,4.0), 15.0]]
[c[(20.0,7.0), 16.0]]
[c[(14.0,18.0), 2.0]]
[c[(20.0,8.0), 17.0]]
[c[(16.0,15.0), -13.0]]
[c[(7.0,6.0), 1.0]]
[c[(11.0,0.0), -15.0]]
error
error
[p(0.0,0.0)]
error
error
[p(0.0,0.0)]
error
error
[p(0.0,0.0)]
error
error
[p(0.0,0.0)]
error
error
[p(0.0,0.0)]
[c[(15.0,2.0), 20.0]]
error
error
[p(0.0,0.0)]
error
error
[p(0.0,0.0)]
error
error
[p(0.0,0.0)]
[c[(3.0,5.0), -7.0]]
error
error
[p(0.0,0.0)]
error
error
[p(0.0,0.0)]
[c[(16.0,5.0), -10.0]]
error
error
[p(0.0,0.0)]
error
error
[p(0.0,0.0)]
[c[(9.0,1.0), -3.0]]
error
error
[p(0.0,0.0)]
error
error
[p(0.0,0.0)]
[c[(13.0,17.0), 7.0]]
error
error
[p(0.0,0.0)]
error
error
[p(0.0,0.0)]
error
error
[p(0.0,0.0)]
[c[(7.0,16.0), 14.0]]
error
error
[p(0.0,0.0)]
[c[(17.0,13.0), -5.0]]
[c[(14.0,8.0), 6.0]]
error
error
[p(0.0,0.0)]
error
error
[p(0.0,0.0)]
error
error
[p(0.0,0.0)]
[c[(13.0,0.0), 14.0]]
[c[(1.0,9.0), 2.0]]
error
error
[p(0.0,0.0)]
[c[(2.0,17.0), -1.0]]
[c[(17.0,8.0), -6.0]]
error
error
[p(0.0,0.0)]
[c[(7.0,19.0), -10.0]]
[c[(20.0,7.0), 3.0]]
error
error
[p(0.0,0.0)]
error
error
[p(0.0,0.0)]
error
error
[p(0.0,0.0)]
[c[(2.0,7.0), -10.0]]
error
error
[p(0.0,0.0)]
[c[(2.0,9.0), 14.0]]
error
error
[p(0.0,0.0)]
[c[(5.0,15.0), 18.0]]
error
error
[p(0.0,0.0)]
[c[(18.0,18.0), -5.0]]
[c[(6.0,2.0), -15.0]]
[c[(12.0,4.0), -3.0]]
error
error
[p(0.0,0.0)]
error
error
[p(0.0,0.0)]
[c[(16.0,0.0), 20.0]]
error
error
[p(0.0,0.0)]
[c[(11.0,12.0), -19.0]]
error
error
[p(0.0,0.0)]
error
error
[p(0.0,0.0)]
[c[(2.0,13.0), 13.0]]
[c[(20.0,2.0), 11.0]]
[c[(0.0,6.0), -10.0]]
error
error
[p(0.0,0.0)]
[c[(17.0,17.0), 7.0]]
error
error
[p(0.0,0.0)]
error
error
[p(0.0,0.0)]
error
error
[p(0.0,0.0)]
error
error
[p(0.0,0.0)]
error
error
[p(0.0,0.0)]
[c[(0.0,16.0), -11.0]]
error
error
[p(0.0,0.0)]
error
error
[p(0.0,0.0)]
error
error
[p(0.0,0.0)]
[c[(14.0,4.0), -2.0]]
[c[(0.0,3.0), 11.0]]
[c[(11.0,15.0), -7.0]]
[c[(19.0,16.0), 19.0]]
[c[(8.0,13.0), 15.0]]

编辑问题：问题是我不能得到0代替负坐标。我需要得到一个正数。

将您的Point类方法更改为：

public void setX(double x) {
    try{ 
        if (x <= 0){
            throw new NegArgumentException();
        }//end if
        else{
            this.x = x;

        }//end else
    }//end try
    catch (NegArgumentException e){
        System.out.println("error");
    }//end catch

}

看看： x <= 0 。 setY也是如此。

再次编辑，要不生成0，请查看此代码：

public class Main {
public static void main(String[] args) {
    //create arraylist for each class
    ArrayList<Point> list = new ArrayList<Point>();
    ArrayList<Rectangle> list1 = new ArrayList<Rectangle>();
    ArrayList<Circle> list2 = new ArrayList<Circle>();
    //create random generators
    Random randomNum = new Random();
    Random myGenerator = new Random();
    int i = 0;
    //go through for loop
    while (i < 100){

        int whichArray = myGenerator.nextInt(4) + 1;
        //print out points for whichever random object
        if (whichArray == 1){
            int pointX = 0;
            while (pointX == 0){
                pointX= randomNum.nextInt(41) - 20;
            }
            int pointY = 0;
            while(pointY == 0){
                pointY = randomNum.nextInt(41) - 20;
            }
            if (pointX >= 0 && pointY >= 0){
                Point point = new Point();
                point.setX(pointX);
                point.setY(pointY);
                list.add(point);
                System.out.println(list.toString());
                list.remove(0);
                i++;
            }
        }//end if
        if (whichArray == 2){
            int pointX = 0;
            while (pointX == 0){
                pointX= randomNum.nextInt(41) - 20;
            }
            int pointY = 0;
            while(pointY == 0){
                pointY = randomNum.nextInt(41) - 20;
            }
            int pointRandom = randomNum.nextInt(20) - 20;
            if (pointX >= 0 && pointY >= 0 && pointRandom >= 0){
                Point point = new Point();
                point.setX(pointX);
                point.setY(pointY);

                Point point2 = new Point();
                point2.setX(pointX+pointRandom);
                point2.setY(pointY-pointRandom);

                list1.add(new Rectangle(point, point2));
                System.out.println(list1.toString());
                list1.remove(0);
                i++;
            }

        }//end if
        if (whichArray == 3){
            int pointX = 0;
            while (pointX == 0){
                pointX= randomNum.nextInt(41) - 20;
            }
            int pointY = 0;
            while(pointY == 0){
                pointY = randomNum.nextInt(41) - 20;
            }
            int radius = randomNum.nextInt(41) - 20;
            if (pointX >= 0 && pointY >= 0){
            list2.add(new Circle(new Point(pointX, pointY),radius));
            System.out.println(list2.toString());
            list2.remove(0);
            i++;
            }
        }//end if

    }//end while loop

}//end main


}//end class

当它为0时，我将继续生成另一个随机数。

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