Java返回值與預期不符

Question

我是新的Java程序員。我正在編寫簡單的程序來計算矩形的面積。您可以輸入矩形的寬度和高度，但問題是我輸入的任何值，面積值總是返回零。我該如何解決這個問題。請看看我的CD。

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()); 
    } 
} 

謝謝...祝您有美好的一天！ :)

Answer 1

你的問題是，你不分配輸入到你的類變量：

private int width; 
private int length; 

但你方法的局部變量String width和String length。

所以，因爲這兩個this.width和this.length沒有改變所以他們0因爲在Java int是默認初始化爲0行return this.width * this.length;將返回0。

您應該將輸入分配給您的類變量。

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：

使用Scanner.nextInt()得到int值，而不是Scanner.nextLine()這將返回一個String，否則你應該分析這些字符串回int。

Answer 2

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

這裏您將寬度放在兩個局部變量中，並返回屬性寬度和高度的多個不同變量。試着用

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

Answer 3

將價值分配到當地的新變量手段，

this.width和this.length未使用，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 4

做這樣的事情在類shape 。

您需要使用這關鍵字

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

這應該可以解決你的問題，兄弟初始化的全局變量寬度和長度！

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 6

使用此代碼也

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;  
    }