如何借助Java的循环编写健壮的程序？

在这里，我们将讨论如何借助循环编写有效的代码。人们普遍认为，使用循环的方法被视为解决问题陈述的幼稚方法。但是，这里仍然有很大的即兴创作范围。所以基本上，循环语句允许我们多次执行一个语句或一组语句。除此之外，我们还可以根据我们的要求操纵它的执行并编写健壮的代码。

假设您要计算圆的面积和周长。新手程序员的一般方法是检查半径是否大于零。如果不是，则打印输入非零正数。现在，这里有什么缺陷？如果用户多次输入小于或等于零的数字，那么我们需要一次又一次地编译我们的代码，因为程序将打印输入非零正数并完成其执行。

示例 1

Java

// Java Program to Simply Get the Area of Shapes
// Without considering robustness into play
  
// Importing Scanner class to
// read input
import java.util.Scanner;
  
// Main class
public class GFG {
  
    // Main driver method
    public static void main(String[] args)
    {
  
        // Creating object of Scanner class to
        // take input
        Scanner s = new Scanner(System.in);
        System.out.println("Enter Radius::");
        double radius = s.nextDouble();
        double perimeter;
        double area;
  
        // If radius is negative
        if (radius <= 0) {
  
            System.out.println(
                "please enter non zero positive number ");
        }
  
        // Radius is positive
        else {
  
            // Compute area and perimeter
            perimeter = 2 * Math.PI * radius;
            area = Math.PI * radius * radius;
  
            // Print and display area and parameter
            System.out.println("Perimeter:: " + perimeter);
            System.out.println("Area:: " + area);
        }
    }
}

输出：

C:\Users\USER\Desktop\Network Java>javac GFG.java
C:\Users\USER\Desktop\Network Java>java GFG
Enter Radius::
-5
please enter non zero positive number
//Execution Finished

C:\Users\USER\Desktop\Network Java>javac GFG.java
C:\Users\USER\Desktop\Network Java>java GFG
Enter Radius::
0
please enter non zero positive number
//Execution Finished

输出说明：

在上面的例子中，我们看到如果用户输入任何非零和负整数，我们需要一次又一次地编译和运行程序。使用 while 循环可以防止这种尴尬的情况。使用循环，我们可以根据我们的要求操纵它的执行并编写健康的代码。

示例 2

Java

// Java program to Illustrate Robustness In a Program
// Using Loops
  
// Importing input output classes
import java.io.*;
  
// Main class
class GFG {
  
    // Main driver method
    public static void main(String[] args)
        throws IOException
    {
        // Custom input - Radius of a circle
        double radius = 50;
  
        // Reading input
        BufferedReader br = new BufferedReader(
            new InputStreamReader(System.in));
  
        // Asking from user to enter radius
        System.out.println("Enter Radius::");
  
        // 1st.This while loop will run since
        // 50>Integer.MIN_VALUE
        while (radius > Integer.MIN_VALUE) {
  
            // 2nd.It's time to read the buffer
            radius = Double.parseDouble(br.readLine()); //**
  
            // 3rd.If radius>0 give result and break the
            // loop.
            if (radius > 0) {
                double Perimeter = 2 * Math.PI * radius;
                double Area = Math.PI * Math.pow(radius, 2);
                System.out.println("Perimeter:: "
                                   + Perimeter);
                System.out.println("Area:: " + Area);
                break;
            }
  
            // 4th.If radius=-100(say) then print the
            // following
            System.out.println(
                "please enter non zero positive number");
            System.out.println("Enter Radius::");
  
            // 5th.As -100>Integer.MIN_VALUE the loop will
            // run again.
        }
    }
}

输出：

C:\Users\USER\Desktop\Network Java>javac GFG.java
C:\Users\USER\Desktop\Network Java>java GFG
Enter Radius::
-10
please enter non zero positive number
Enter Radius::
0
please enter non zero positive number
Enter Radius::
3
Perimeter:: 18.84955592153876
Area:: 28.274333882308138
//Execution Finished

Note: In the above program, we see if we read the buffer once then, it will no longer store anything. If we try to read it again then it will ask for input.