具有多个方法和构造函数的 Java Box 程序

Question

我是编程初学者，特别是在使用构造函数时遇到问题。我必须为我的一个实验室编写一个程序，该程序必须仅包含:

1. Three instance variables – length, width and height (each of type double)
   2. One instance variables – input (type Scanner) initialized to System.in
   3. Default constructor (no-arg) – initialize all three instance variables to 1
   4. Initial constructor – initialize all three instance variables
   5. Copy constructor – copy Box
   6. inputWidth, inputLength, and inputHeight methods that set the instance variables based on user input have not parameters and do not return a value.
   7. a displayDimensions method that displays the length X Width X height (separated by “X”) and does not return a value.
   8. a calcVolume method that has no parameters and calculates the volume of the box

We also were given application BoxTest in which the output must exactly match the following:

• Default dimensions are 1.0 X 1.0 X 1.0 with volume of 1.0
• Initial dimensions are 8.5 X 11.0 X 1.0 with volume of 93.5
• Copied dimensions are 8.5 X 11.0 X 1.0 with volume of 93.5
• Update dimensions
• Enter length: 1
• Enter width: 2
• Enter height: 3
• Updated dimensions are 1.0 X 2.0 X 3.0 with volume of 6.0

这是我的代码:

import java.util.Scanner;

public class Box {
public static void main(String args[]) {
    double length, width, height;

    Scanner input=new Scanner(System.in);

new Box() {     //  

Box defaultBox=new Box();
    double length = 1.0;
    double width = 1.0;
    double height = 1.0;
    System.out.print("Default dimensions are " + length + " X " + width + " X " + height);
    defaultBox.displayDimensions();
    System.out.println(" with volume of "+defaultBox.calcVolume());

Box initialBox=new Box(length, width, height);
    length = 8.5;
    width = 11.0;
    height = 1.0;
    System.out.print("Initial dimensions are " + length + " X " + width + " X " + height);
    initialBox.displayDimensions();
    System.out.println(" with volume of "+initialBox.calcVolume());

Box copyBox=new Box(initialBox);
    System.out.print("Copied dimensions are " + length + " X " + width + " X " + height);
    copyBox.displayDimensions();
    System.out.println(" with volume of "+copyBox.calcVolume());

    System.out.println("\nUpdate dimensions");
    initialBox.inputLength();
    initialBox.inputWidth();
    initialBox.inputHeight();
    System.out.print("Updated dimensions are ");
    initialBox.displayDimensions();
    System.out.println(" with volume of "+initialBox.calcVolume());
}
double inputLength() {
    Scanner input;
    double length = input.nextDouble(); 
    }
double inputWidth() {
    Scanner input;
    double width = input.nextDouble();
    }
double inputHeight() {
    Scanner input;
    double height = input.nextDouble();
    }

double displayDimensions(double length, double width, double height) {   
    Scanner input;
    }

double calcVolume() {
}

}

我错过了什么？我的程序无法编译并给出错误消息

Exception in thread "main" java.lang.Error: Unresolved compilation problems: 
    Syntax error, insert "Identifier (" to complete MethodHeaderName
    Syntax error, insert ")" to complete MethodDeclaration
    Syntax error, insert ";" to complete MethodDeclaration
    Syntax error, insert "}" to complete ClassBody
at Box.main(Box.java:18)

Answer 1

正如我在评论中所说，您已将所有内容放入 main 中。不要那样做。事实上，您的 Box 类基本上是空的，并且您当前几乎在 main 中创建一个匿名子类。您的指示没有提及 main，但非常简单。你应该写一些类似的东西

public class Box {
    // Three instance variables – length, width and height (each of type double)
    private double length, width, height;
    // One instance variables – input (type Scanner) initialized to System.in
    private Scanner input = new Scanner(System.in);

    // Default constructor (no-arg) – initialize all three instance variables to 1
    public Box() {
        this.length = this.width = this.height = 1;
    }

    // Initial constructor – initialize all three instance variables
    public Box(double length, double width, double height) {
        this.length = length;
        this.width = width;
        this.height = height;
    }

    // Copy constructor – copy Box
    public Box(Box b) {
        this(b.length, b.width, b.height);
    }

    // inputWidth, inputLength, and inputHeight methods that set the instance
    // variables based on user input have not parameters and do not return a value.
    public void inputWidth() {
        this.width = input.nextDouble();
    }

    public void inputLength() {
        this.length = input.nextDouble();
    }

    public void inputHeight() {
        this.height = input.nextDouble();
    }

    // a displayDimensions method that displays the length X Width X height
    // (separated by “X”) and does not return a value.
    public void displayDimensions() {
        System.out.printf("%.2fX%.2fX%.2f%n", length, width, height);
    }

    // a calcVolume method that has no parameters and calculates the volume of the
    // box
    public double calcVolume() {
        return length * width * height;
    }
}