如何結束程序並停止提示用戶？

Question

當用戶輸入的寬度小於或等於0時，程序應該結束，並且不會提示用戶輸入長度，或輸出區域或邊界。我如何做到這一點，而不使用System.exit（0）？！？

public static void main(String[] args) { 
    Scanner k = new Scanner (System.in); 
    System.out.print("Please Enter a Width: "); 
    double width = k.nextDouble(); 
    System.out.print("Please Enter a Length: "); 
    double length = k.nextDouble(); 
    double area = width * length; 
    System.out.println("The Area is: " + area); 
    double perimeter = 2 * (width + length); 
    System.out.println("The Perimeter is: " + perimeter); 

    if (width <=0) 
     System.out.println("The Width Must Be Greater Than 0"); 

    else if (length <=0) 
     System.out.println("The Length Must Be Greater Than 0"); 

    if (width == length) 
    System.out.println("The Shape is a Square"); 

    else if (width != length) 
    System.out.println("The Shape is a Rectangle");  

Answer 1

您可以隨時與return

跳出的方法在您的情況：

... 
System.out.print("Please Enter a Width: "); 
double width = k.nextDouble(); 
if (width <= 0) 
    return; 
... 

Answer 2

更改條件語句，使代碼的其餘部分執行僅在寬度較大比0：

Scanner k = new Scanner (System.in); 
System.out.print("Please Enter a Width: "); 
double width = k.nextDouble(); 
if (width <=0) 
{ 
    System.out.println("The Width Must Be Greater Than 0"); 
} 
else 
{ 
    System.out.print("Please Enter a Length: "); 
    double length = k.nextDouble(); 
    double area = width * length; 
    System.out.println("The Area is: " + area); 
    double perimeter = 2 * (width + length); 
    System.out.println("The Perimeter is: " + perimeter); 
    if (length <=0) 
     System.out.println("The Length Must Be Greater Than 0"); 
    if (width == length) 
     System.out.println("The Shape is a Square"); 
    else if (width != length) 
     System.out.println("The Shape is a Rectangle"); 
} 

Answer 3

如果width小於零，該程序將退出並且不會提示用戶輸入length。我已經將該邏輯擴展爲length提示，因此如果length小於0，程序也會停止。

工作過brso05'的邏輯，我想出了以下建議：

Scanner k = new Scanner (System.in); 
System.out.print("Please Enter a Width: "); 
double width = k.nextDouble(); 

if (width <=0){ 
    System.out.println("The Width Must Be Greater Than 0"); 
} 
else{ 
    System.out.print("Please Enter a Length: "); 
    double length = k.nextDouble(); 

    if (length <=0){ 
     System.out.println("The Length Must Be Greater Than 0"); 
    } 
    else{ 
     double area = width * length; 
     System.out.println("The Area is: " + area); 
     ... 
    } 
}