理解方法

Question

在下面的代码中，我创建了一个程序，根据用户输入的行数来打印三角形。

我的问题是：我正在主方法中进行所有计算，但是如何通过拆分此程序并将循环放在自己的方法中并将其调用到main方法中来解决这个问题？

public class Triangle {

  public static void main(String[] args) {


         //declare a scanner for user input 
         Scanner input = new Scanner (System.in);



         System.out.print("Enter the number of lines: ");
          int numLines = input.nextInt();

          //include an if statement to make sure that the number of lines that 
           the user inputs is greater than zero
            if (numLines <= 0)
                {
                    System.out.println("Number of lines is negative. Exiting.");
                    System.exit(0);
                }


    //This for loops prints one line for each iteration.
    for(int i=0;i<numLines;i++)
    {
        //This for loop takes care of the preceding spaces in each line.
        for(int j=0;j<numLines-i-1;j++)
            System.out.print(" ");

        //This for loop prints the required number of characters in each line.
        for(int k=0;k<=i;k++)
            System.out.print("* ");

        //We are done with a line. Moving on to the next one.
        System.out.println();
    }


 }
}

Answer 1

你也可以这样做：

import java.util.Scanner;

public class Triangle {

    // declare a scanner for user input
    Scanner input = new Scanner(System.in);

    public int getInput() { // method to take user input

        System.out.print("Enter the number of lines: ");
        int numLines = input.nextInt();

        // include an if statement to make sure that the number of lines that
        // the user inputs is greater than zero
        if (numLines <= 0) {
            System.out.println("Number of lines is negative. Exiting.");
            System.exit(0);
        }
        return numLines;
    }

    public void printTriangle() {
        int numLines = getInput();
        // This for loops prints one line for each iteration.
        for (int i = 0; i < numLines; i++) {
            // This for loop takes care of the preceding spaces in each line.
            for (int j = 0; j < numLines - i - 1; j++)
                System.out.print(" ");

            // This for loop prints the required number of characters in each
            // line.
            for (int k = 0; k <= i; k++)
                System.out.print("* ");

            // We are done with a line. Moving on to the next one.
            System.out.println();
        }
    }

    public static void main(String[] args) {
        Triangle obj = new Triangle(); // create object
        obj.printTriangle(); // call using object
    }
}

这里我们创建两个函数：

• getInput（）从用户获取输入并将numLines返回给调用者。
• printTriangle（）打印图案

最后，我们创建了Triangle类的对象并调用了printTriangle（）。

Triangle obj = new Triangle(); // create object
        obj.printTriangle(); // call using object