Java返回值不符合预期

Question

我是新的Java程序员。我正在写一个简单的程序来计算矩形的面积。您可以输入矩形的宽度和高度，但问题是无论我输入什么值，面积值总是返回零。如何解决此问题。请看一下我的cde

import java.util.Scanner;
public class Shape {
    private int area;
    private int width;
    private int length;
    private String name;

    public String shapeName() {
     Scanner scanner = new Scanner(System.in);
     System.out.print("Enter shape name: ");
     String name = scanner.nextLine();
     return name;
    }

    public int area() {
     Scanner scanner = new Scanner(System.in);
     System.out.print("Enter width: ");
     String width = scanner.nextLine();  
     System.out.print("Enter height: ");
     String height = scanner.nextLine();
     return this.width * this.length;       
    }
}
public class Example1 {

    public static void main(String[] args) {
        // TODO Auto-generated method stub

        Shape shape = new Shape();
        System.out.println("Shape is " + shape.shapeName());
        System.out.println("It's area is " + shape.area());
    }
}

谢谢。。。祝你今天愉快！：）

Answer 1

     String width = scanner.nextLine();  
     System.out.print("Enter height: ");
     String height = scanner.nextLine();
     return this.width * this.length;       
    }

在这里，您将宽度放在两个局部变量中，并返回属性width和height的mul，这两个变量是不同的。试一试

this.width = scanner.nextInt();
System.out.print("Enter height: ");
this.height = scanner.nextInt();
return this.width * this.length;  

Answer 2

这会解决你的问题，兄弟

public int area() {
     Scanner scanner = new Scanner(System.in);
     System.out.print("Enter width: ");
     int width = Integer.parseInt(scanner.nextLine());
     this.width = width;  
     System.out.print("Enter height: ");
     int height = Integer.parseInt(scanner.nextLine());
     this.height = height;
     return this.width * this.length;       
    }

Answer 3

您的问题是没有将输入分配给类变量：

private int width;
private int length;

但是对于您的方法，局部变量是String width和String length

因此return this.width * this.length;行将返回0，因为this.width和this.length都没有更改，所以它们是0，因为在Java中int默认初始化为0

您应该将输入分配给类变量

 public int area() {
      Scanner scanner = new Scanner(System.in);
      System.out.print("Enter width: ");
      width = scanner.nextInt();  
      System.out.print("Enter height: ");
      length = scanner.nextInt();
      return width * length;       
}

注意：

使用Scanner.nextInt()获取int值，而不是返回String的Scanner.nextLine()，否则应将这些字符串解析回int

Answer 4

在课堂上做这样的动作

您需要使用这个关键字初始化全局变量宽度和长度

class Shape {
private int area;
private int width;
private int length;
private String name;

public String shapeName() {
 Scanner scanner = new Scanner(System.in);
 System.out.print("Enter shape name: ");
 String name = scanner.nextLine();
 return name;
}

public int area() {
 Scanner scanner = new Scanner(System.in);
 System.out.print("Enter width: ");
 int width = scanner.nextInt();  
 System.out.print("Enter lengtht: ");
 int length = scanner.nextInt();
 this.width = width;
 this.length=length;
 return this.width * this.length;       
}
}

Answer 5

将值赋给局部新变量意味着

这个。宽度和这个。未使用长度，因此返回0

public int area() {
    Scanner scanner = new Scanner(System.in);
    System.out.print("Enter width: ");
    this.width = scanner.nextInt();  
    System.out.print("Enter height: ");
    this.height = scanner.nextInt();
    return this.width * this.length;       
}

Answer 6

也可以使用此代码

public double area(){
     Scanner scanner = new Scanner(System.in);
     System.out.print("Enter width: ");
     int width = scanner.nextInt();  
     System.out.print("Enter height: ");
     int height = scanner.nextInt();
      double d=width*height;
     return d;       
    }