如何解决Java抽象类的输出出现问题
我正在尝试从抽象类中的方法中打印值。有一个switch语句调用抽象方法，并有一个语句打印数组中的项目。我尝试了案例1（添加新圆），然后尝试了案例6（显示形状）。
说明符或情况6的调用语句可能有问题吗？
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("1 Add a new circle");
System.out.println("2 Add a new rectangle");
System.out.println("3 Add a new right triangle");
System.out.println("4 Delete a shape");
System.out.println("5 Delete all shape");
System.out.println("6 display all shapes");
System.out.println("7 Move a shape");
System.out.println("8 Enter a scale factor");
System.out.println("9 Scale all shapes");
System.out.println("10 Exit program");
// get user choice
selection = input.nextInt();
while (selection < 1 || selection > 10)
{
System.out.println("Please enter valid choice");
selection = input.nextInt();
}
// switch on selection
switch(selection)
{
case 1:
// ADD NEW CIRCLE
System.out.println("Enter radius for your circle: ");
radius = input.nextDouble();
// get size from user (one variable)
// get location from user (two variables)
System.out.println("Enter x location for your circle: ");
x = input.nextDouble();
System.out.println("Enter y location for your circle: ");
y = input.nextDouble();
// set found to 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("Array is full. ERROR");
}
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("Enter height of rectagle: ");
height = input.nextDouble();
System.out.println("Enter width of rectagle: ");
width = input.nextDouble();
// get location from user (two variables)
System.out.println("Enter x location for your rectangle: ");
x = input.nextDouble();
System.out.println("Enter y location for your rectangle: ");
y = input.nextDouble();
// set found to false
found = false;
for (int i = 0; i< shapes.length;i++) {
if(shapes[i] != null) {
shapes[i] = new Rectangle(nextIDNumber++,height,width);
found = true;
break;
}
}
if(!found) {
System.out.println("ERROR");
}
break;
case 3:
// ADD NEW RIGHT TRIANGLE
// get size from user (two variables)
System.out.println("Enter the base: ");
base = input.nextDouble();
while (base <= 0)
{
System.out.println("Invalid number,please enter positive number");
base = input.nextDouble();
}
System.out.println("Enter the height");
height = input.nextDouble();
while (height <= 0)
{
System.out.println("Invalid number,please enter positive number");
height = input.nextDouble();
}
// get location from user (two variables)
System.out.println("Enter X location");
x = input.nextDouble();
while (x < 0)
{
System.out.println("Invalid number,please enter positive number or zero");
x = input.nextDouble();
}
System.out.println("Enter Y location");
y = input.nextInt();
while (y < 0)
{
System.out.println("Invalid number,please enter positive number or zero");
y = input.nextDouble();
}
// set found to false
found = false;
// loop through array
for (int i = 0; i < 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++,base,height);
// set found to true
found = true;
// break out of loop
break;
}
}
// if not found,give error message
if (!found)
{
System.out.println("No more room");
}
// break out of switch statement
break;
case 4:
// DELETE ONE SHAPE
// get id number to delete
System.out.println("Enter ID of shape to be deleted: ");
id = input.nextInt();
found = false;
for (int i = 0; i< shapes.length; i++) {
if (id == shapes[i].getID() && shapes[i] != null) {
shapes[i] = null;
found = true;
break;
}
}
if (!found) {
System.out.println("Shape not found.");
}
break;
case 5:
// DELETE ALL SHAPES
System.out.println("Are you sure you want to delete all shapes? 1] YES 2] NO : ");
int choice = input.nextInt();
if(choice == 1) {
for (int i= 0; i<shapes.length; i++) {
if(shapes[i]!=null) {
shapes[i] = null;
}
}
}
break;
case 6:
// disPLAY ALL SHAPES
// print header
System.out.println("Here are our shapes");
System.out.printf("%10s %10s %10s %10s %10s\n","ID","X","Y","AREA","PERIMETER");
for (int i = 0; i<shapes.length;i++) {
if (shapes[i] != null) {
System.out.printf("%10d %10.2f %10.2f %10.2f %10f\n",shapes[i].getID(),shapes[i].getxLoc(),shapes[i].getyLoc(),shapes[i].getArea(),shapes[i].getPerimiter() );
}
}
break;
case 7:
// MOVE A SHAPE
System.out.println("Enter the ID of shape:");
id = input.nextInt();
System.out.println("Enter X location of shape:");
x = input.nextDouble();
System.out.println("Enter Y location of shape:");
y = input.nextDouble();
found = false;
for(int i =0; i<shapes.length;i++) {
if(id == shapes[i].getID() && shapes[i] != null) {
shapes[i].setxLoc(x);
shapes[i].setxLoc(y);
found = true;
break;
}
}
if (!found) {
System.out.println("Not found.");
}
break;
case 8:
// ENTER A SCALE FACTOR
System.out.println("Enter scale factor: ");
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<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("Do you want to exit? \n1] YES\n2] NO");
int user = input.nextInt();
if(user == 1) {
System.out.println("Thank you!");
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 > 0) {
Shape.scaleFactor = scaleFactor;
}
}
public int getID() {
return id;
}
public void setID(int i) {
if (i > 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 y,double r){
super(i,y);
r = radius;
}
// get/set methods
public double geTradius()
{
return radius;
}
public void seTradius(double r)
{
if (r > 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);
}
}
解决方法
您在构造函数中的分配错误，因此与形状关联的值全为零。您需要切换它们。该构造函数：
// one constructor
public Shape(int i,double x,double y) {
i = id;
x = xLoc;
y = yLoc;
}
应该是这样：
public Shape(int i,double y) {
id = i;
xLoc = x;
yLoc = y;
}
这：
public Circle (int i,double y,double r){
super(i,x,y);
r = radius;
}
应该是这样：
public Circle (int i,y);
radius = r;
}
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