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Java 没有抛出异常消息

java class exception

Java 没有抛出异常消息,java,class,exception,coordinates,Java,Class,Exception,Coordinates,嘿，我有一个point类，它生成一个点列表。课程安排如下 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()

嘿，我有一个point类，它生成一个点列表。课程安排如下

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 + ")";
}
}
}

我还有另外两个类矩形和圆形

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()+")]";
}
}
还有圆圈班

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点列表

import java.util.ArrayList;
导入java.util.Random

公共班机{

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

publicstaticvoidmain（字符串[]args）{
//为每个类创建arraylist
ArrayList=新建ArrayList（）；
ArrayList list1=新的ArrayList（）；
ArrayList list2=新的ArrayList（）；
//创建随机生成器
随机点=新随机点（）；
Random myGenerator=新的Random（）；
int i=0；
//循环
而（i<100）{
int whichArray=myGenerator.nextInt（4）+1；
//打印任意随机对象的点
如果（whichArray==1）{
int pointX=Point.nextInt（41）-20；
int pointY=Point.nextInt（41）-20；
如果（点X>=0&&pointY>=0）{
添加（新点（点x，点y））；
System.out.println（list.toString（））；
列表。删除（0）；
i++；
}
}//如果结束
如果（whichArray==2）{
int pointX=Point.nextInt（41）-20；
int pointY=Point.nextInt（41）-20；
int pointRandom=Point.nextInt（20）-20；
如果（pointX>=0&&pointY>=0&&pointRandom>=0）{
列表1.add（新矩形（新点（pointX，pointY）），新点（pointX+pointRandom，pointY-pointRandom））；
System.out.println（list1.toString（））；
列表1.删除（0）；
i++；
}
}//如果结束
如果（whichArray==3）{
int pointX=Point.nextInt（41）-20；
int pointY=Point.nextInt（41）-20；
int半径=下一点（41）-20；
如果（点X>=0&&pointY>=0）{
列表2.添加（新圆（新点（点X、点Y、半径））；
System.out.println（list2.toString（））；
清单2.删除（0）；
i++；
}
}//如果结束
}//边结束边循环
}//端干管
}//末级
问题是，我没有看到异常发生时显示的任何消息。我知道这是有效的，因为我的点没有负坐标。有人知道为什么没有显示消息吗？

您的代码中有很多错误做法，您应该阅读一些关于编写干净代码的内容。顺便说一下，不会引发异常，因为从未调用setter。将构造函数更改为

public Point(double x, double y) {    
    setX(x);
    setY(y);   
}
另外，在创建点之前，您始终确保
if
语句的坐标为正，因此无法实例化无效的
点


最后，即使它与您的“问题”无关，也不要给变量（您的
Random
对象）起一个以大写字母开头的名称，这对于可读性来说是一种不好的做法，如果它也是类的名称，则更糟糕<如果类
Point
和类
Random
中都存在
method
方法，则code>Point.method（）
可能不明确。您正在构造函数内设置
Point
的值：


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


所以，永远不会调用setX和setY，所以永远不会验证x和y是否为负数

试着这样做：


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


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：问题是我不能用0代替负坐标。我需要一个正数

将点类方法更改为：


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

}



当它为0时，我将继续生成另一个随机数。
何时以及为什么会发生异常？我看到
如果（pointX>=0&&pointY>=0）
到处都有守卫！问题是当我把这些都处理掉，任何本来是负数的数字都会变为0，所以我的随机坐标的0比它应该的多@ElliottFrisch为什么不只是你想开始的范围？我希望，但我的赋值特别声明，当我执行你的方法时，捕捉出现在@ElliottFrisch的任何负数，它告诉我，该方法对于类型是未定义的随机的当我试着施法时，它说不能施法。问题是我不能用0来代替负坐标。我需要得到一个正数。再次为您编辑。我非常感谢您的帮助，但我仍然得到一个异常数量的0。我认为问题可能在于，对于随机生成器吐出的每个负数，它都将这些坐标初始化为0。我需要它来重新生成一个新的随机坐标，直到我得到一个正数。好的，我现在明白了，我读了random.nextInt的规范，它说“返回一个伪随机的，均匀分布的int值，介于0（包含）和指定值（独占）”之间，所以0可能发生，我会尽力帮你解决这个问题

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]]



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 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