在Java中关于抽象类输出的问题。

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英文:

Trouble with output from abstract classes in java

问题

以下是你提供的代码的中文翻译部分:

我正在尝试从抽象类的方法中打印值有一个switch语句调用抽象方法和一个打印数组中项的语句我尝试了case 1添加新的圆),然后是case 6显示形状)。

![输出图像][1]

可能是说明符或在case 6中进行的调用语句有问题吗

package lab8;
import java.util.Scanner;
public class test {
public static void main(String args[])
{
    // 数据
    Shape[] shapes = new Shape[10];
    int nextIDNumber = 1;
    boolean exit = false;
    int selection;
    Scanner input = new Scanner(System.in);
    int id;
    double x, y;
    double base = 0, height = 0, width = 0, radius = 0, scaleFactor;
    boolean found = false;

    // 算法
    // 循环直到用户退出
    do
    {
        // 显示菜单
        System.out.println("1 添加新圆");
        System.out.println("2 添加新矩形");
        System.out.println("3 添加新直角三角形");
        System.out.println("4 删除形状");
        System.out.println("5 删除所有形状");
        System.out.println("6 显示所有形状");
        System.out.println("7 移动形状");
        System.out.println("8 输入比例因子");
        System.out.println("9 缩放所有形状");
        System.out.println("10 退出程序");

        // 获取用户选择
        selection = input.nextInt();
        while (selection < 1 || selection > 10)
        {
            System.out.println("请输入有效的选项");
            selection = input.nextInt();
        }

        // 根据选择进行切换
        switch(selection)
        {
        case 1:
            // 添加新圆
            System.out.println("输入您的圆的半径:");
            radius = input.nextDouble();
            // 从用户获取大小(一个变量)

            // 从用户获取位置(两个变量)
            System.out.println("输入您的圆的x位置:");
            x = input.nextDouble();
            System.out.println("输入您的圆的y位置:");
            y = input.nextDouble();
            // 设置found为false
            found = false;
            for(int i = 0; i < shapes.length; i++) {
                if (shapes[i] == null) {
                    shapes[i] = new Circle (nextIDNumber++, x, y, radius);
                    found = true;
                    break;
                }
            }
            if(!found) {
                System.out.println("数组已满。错误");
            }
            break;

            // 循环遍历数组
                // 如果这不是一个有效的对象
                 // 创建新的Circle对象并分配给当前数组元素

                    // 将found设置为true

                    // 退出循环

            // 如果未找到,则给出错误消息

            // 退出switch语句

        case 2:
            // 添加新矩形
            // 从用户获取大小(两个变量)
            System.out.println("输入矩形的高度:");
            height = input.nextDouble();
            System.out.println("输入矩形的宽度:");
            width = input.nextDouble();
            // 从用户获取位置(两个变量)
            System.out.println("输入矩形的x位置:");
            x = input.nextDouble();
            System.out.println("输入矩形的y位置:");
            y = input.nextDouble();
            // 设置found为false
            found = false;

            for (int i = 0; i< shapes.length;i++) {
                if(shapes[i] != null) {
                    shapes[i] = new Rectangle(nextIDNumber++, x,y, height, width);
                    found = true;
                    break;
                }
            }
            if(!found) {
                System.out.println("错误");
            }
            break;

        // 其他case类似,省略...
    }
} while (!exit);

}

// 抽象类Shape
abstract class Shape
{
    // 声明静态变量
    public static double scaleFactor;

    // 声明实例变量
    private int id;
    private double xLoc;
    private double yLoc;
    
    // 一个构造方法
    public Shape(int i, double x, double y) {
        i = id;
        x = xLoc;
        y = yLoc;
    }

    // 获取/设置方法,抽象方法...
}

// Circle类,类似的还有其他几个类...
class Circle extends Shape
{
    // 声明实例变量
    private double radius;
    
    public Circle (int i, double x, double y, double r){
        super(i, x, y);
        r = radius;
    }

    // 获取/设置方法,重写抽象方法...
}

注意:由于篇幅较长,我只翻译了你提供的代码的部分内容。如果你需要其他部分的翻译,请继续提供需要翻译的代码。

英文:

I am trying to print values from methods in an abstract class. There is a switch statement that calls abstract methods and a statement that prints items in the array. I tried case 1 (Add new circle) and then case 6(Display shapes.

在Java中关于抽象类输出的问题。

Could be problem with specifiers or with call statements made in case 6?

package lab8;
import java.util.Scanner;
public class test {
public static void main(String args[])
{
// DATA
Shape[] shapes = new Shape[10];
int nextIDNumber = 1;
boolean exit = false;
int selection;
Scanner input = new Scanner(System.in);
int id;
double x, y;
double base = 0, height = 0, width = 0, radius = 0, scaleFactor;
boolean found = false;
// ALGORITHM
// loop until user exits
do
{
// display menu
System.out.println(&quot;1 Add a new circle&quot;);
System.out.println(&quot;2 Add a new rectangle&quot;);
System.out.println(&quot;3 Add a new right triangle&quot;);
System.out.println(&quot;4 Delete a shape&quot;);
System.out.println(&quot;5 Delete all shape&quot;);
System.out.println(&quot;6 Display all shapes&quot;);
System.out.println(&quot;7 Move a shape&quot;);
System.out.println(&quot;8 Enter a scale factor&quot;);
System.out.println(&quot;9 Scale all shapes&quot;);
System.out.println(&quot;10 Exit program&quot;);
// get user choice
selection = input.nextInt();
while (selection &lt; 1 || selection &gt; 10)
{
System.out.println(&quot;Please enter valid choice&quot;);
selection = input.nextInt();
}
// switch on selection
switch(selection)
{
case 1:
// ADD NEW CIRCLE
System.out.println(&quot;Enter radius for your circle: &quot;);
radius = input.nextDouble();
// get size from user (one variable)
// get location from user (two variables)
System.out.println(&quot;Enter x location for your circle: &quot;);
x = input.nextDouble();
System.out.println(&quot;Enter y location for your circle: &quot;);
y = input.nextDouble();
// set found to false
found = false;
for(int i = 0; i &lt; shapes.length; i++) {
if (shapes[i] == null) {
shapes[i] = new Circle (nextIDNumber++, x, y, radius);
found = true;
break;
}
}
if(!found) {
System.out.println(&quot;Array is full. ERROR&quot;);
}
break;
// loop through array
// if this is not a valid object
// create new Circle object and assign to current array element
// set found to true
// break out of loop
// if not found, give error message
// break out of switch statement
case 2:
// ADD NEW RECTANGLE
// get size from user (two variables)
System.out.println(&quot;Enter height of rectagle: &quot;);
height = input.nextDouble();
System.out.println(&quot;Enter width of rectagle: &quot;);
width = input.nextDouble();
// get location from user (two variables)
System.out.println(&quot;Enter x location for your rectangle: &quot;);
x = input.nextDouble();
System.out.println(&quot;Enter y location for your rectangle: &quot;);
y = input.nextDouble();
// set found to false
found = false;
for (int i = 0; i&lt; shapes.length;i++) {
if(shapes[i] != null) {
shapes[i] = new Rectangle(nextIDNumber++, x,y, height, width);
found = true;
break;
}
}
if(!found) {
System.out.println(&quot;ERROR&quot;);
}
break;
case 3:
// ADD NEW RIGHT TRIANGLE
// get size from user (two variables)
System.out.println(&quot;Enter the base: &quot;);
base = input.nextDouble();
while (base &lt;= 0)
{
System.out.println(&quot;Invalid number, please enter positive number&quot;);
base = input.nextDouble();
}
System.out.println(&quot;Enter the height&quot;);
height = input.nextDouble();
while (height &lt;= 0)
{
System.out.println(&quot;Invalid number, please enter positive number&quot;);
height = input.nextDouble();
}
// get location from user (two variables)
System.out.println(&quot;Enter X location&quot;);
x = input.nextDouble();
while (x &lt; 0)
{
System.out.println(&quot;Invalid number, please enter positive number or zero&quot;);
x = input.nextDouble();
}
System.out.println(&quot;Enter Y location&quot;);
y = input.nextInt();
while (y &lt; 0)
{
System.out.println(&quot;Invalid number, please enter positive number or zero&quot;);
y = input.nextDouble();
}
// set found to false
found = false;
// loop through array
for (int i = 0; i &lt; shapes.length; i++)
{
// if this is not a valid object
if (shapes[i] == null)
{
// create new RightTriangle object and assign to current array element
shapes[i] = new RightTriangle(nextIDNumber++, x, y, base, height);
// set found to true
found = true;
// break out of loop
break;
}
}
// if not found, give error message
if (!found)
{
System.out.println(&quot;No more room&quot;);
}
// break out of switch statement
break;
case 4:
// DELETE ONE SHAPE
// get id number to delete
System.out.println(&quot;Enter ID of shape to be deleted: &quot;);
id = input.nextInt();
found = false;
for (int i = 0; i&lt; shapes.length; i++) {
if (id == shapes[i].getID() &amp;&amp; shapes[i] != null) {
shapes[i] = null;
found = true;
break;
}
}
if (!found) {
System.out.println(&quot;Shape not found.&quot;);
}
break;
case 5:
// DELETE ALL SHAPES
System.out.println(&quot;Are you sure you want to delete all shapes? 1] YES 2] NO : &quot;);
int choice = input.nextInt();
if(choice == 1) {
for (int i= 0; i&lt;shapes.length; i++) {
if(shapes[i]!=null) {
shapes[i] = null;
}
}
}
break;
case 6:
// DISPLAY ALL SHAPES
// print header
System.out.println(&quot;Here are our shapes&quot;);
System.out.printf(&quot;%10s %10s %10s %10s %10s\n&quot;, &quot;ID&quot;, &quot;X&quot;, &quot;Y&quot;, &quot;AREA&quot;, &quot;PERIMETER&quot;);
for (int i = 0; i&lt;shapes.length;i++) {
if (shapes[i] != null) {
System.out.printf(&quot;%10d %10.2f %10.2f %10.2f %10f\n&quot;, shapes[i].getID(),shapes[i].getxLoc(),shapes[i].getyLoc(),shapes[i].getArea(),
shapes[i].getPerimiter() );
}
}
break;
case 7:
// MOVE A SHAPE
System.out.println(&quot;Enter the ID of shape:&quot;);
id = input.nextInt();
System.out.println(&quot;Enter X location of shape:&quot;);
x = input.nextDouble();
System.out.println(&quot;Enter Y location of shape:&quot;);
y = input.nextDouble();
found = false;
for(int i =0; i&lt;shapes.length;i++) {
if(id == shapes[i].getID() &amp;&amp; shapes[i] != null) {
shapes[i].setxLoc(x);
shapes[i].setxLoc(y);
found = true;
break;
}
}
if (!found) {
System.out.println(&quot;Not found.&quot;);
}
break;
case 8:
// ENTER A SCALE FACTOR
System.out.println(&quot;Enter scale factor: &quot;);
scaleFactor = input.nextDouble();
Shape.setScaleFactor(scaleFactor);
break;
// get scale factor
// call SetScaleFactor to set the new scale factor
// break out of switch statement
case 9:
// SCALE ALL SHAPES
for(int i =0;i&lt;shapes.length;i++) {
if (shapes[i] != null) {
shapes[i].scaleShape();
}
}
// loop through array
// if this is a valid object
// call ScaleShape
// break out of switch statement
break;
case 10:
System.out.println(&quot;Do you want to exit? \n1] YES\n2] NO&quot;);
int user = input.nextInt();
if(user == 1) {
System.out.println(&quot;Thank you!&quot;);
exit = true;
}
break;
// EXIT PROGRAM
// confirm user wants to exit
// set variable to break out of loop
// break out of switch statement
}
} while (!exit);
}

}

abstract class Shape
{
// declare static variable
public static double scaleFactor;
// declare instance variables
private int id;
private double xLoc;
private double yLoc;
// one constructor
public Shape(int i, double x, double y) {
i = id;
x = xLoc;
y = yLoc;
}
// get/set methods
public static double getScaleFactor() {
return scaleFactor;
}
public static void setScaleFactor(double scaleFactor) {
if (scaleFactor &gt; 0) {
Shape.scaleFactor = scaleFactor;
}
}
public int getID() {
return id;
}
public void setID(int i) {
if (i &gt; 0 ) {
i = id;
}
}
public double getxLoc() {
return xLoc;
}
public void setxLoc(double x) {
x = xLoc;
}
public double getyLoc() {
return yLoc;
}
public void setyLoc(double y) {
y = yLoc;
}
// abstract methods
public abstract double getArea();
public abstract double getPerimiter();
public abstract void scaleShape();
}
class Circle extends Shape
{
// declare instance variable
private double radius;
public Circle (int i, double x, double y, double r){
super(i, x, y);
r = radius;
}
// get/set methods
public double getRadius()
{
return radius;
}
public void setRadius(double r)
{
if (r &gt; 0.0)
{
radius = r;
}
}
// override abstract methods
// GetPerimeter method
public  double getPerimiter() {
return 2 * Math.PI * radius;
}
// GetArea method
public double getArea()	{
return Math.PI * radius * radius;
}
// ScaleShape method
public void scaleShape() {
radius = radius * scaleFactor;
setRadius(radius);
}
}

答案1

得分: 0

你在构造函数中赋值的方式有误,导致与形状相关的值全部为零。你需要进行调整。下面是正确的构造函数示例:

第一个构造函数:

public Shape(int i, double x, double y) {
    id = i;
    xLoc = x;
    yLoc = y;
}

第二个构造函数:

public Circle (int i, double x, double y, double r){
    super(i, x, y);
    radius = r;
}
英文:

You have your assignments wrong in your constructors, so the values associated with your shapes are all zero. You need to switch them around. This constructor:

// one constructor
public Shape(int i, double x, double y) {
i = id;
x = xLoc;
y = yLoc;
}

should be this:

public Shape(int i, double x, double y) {
id = i;
xLoc = x;
yLoc = y;
}

and this:

    public Circle (int i, double x, double y, double r){
super(i, x, y);
r = radius;
}

should be this:

public Circle (int i, double x, double y, double r){
super(i, x, y);
radius = r;
}

huangapple
  • 本文由 发表于 2020年10月25日 23:18:22
  • 转载请务必保留本文链接:https://go.coder-hub.com/64525346.html
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