Question

我尝试将do-while转换为while循环，程序甚至编译，但没有任何反应。原始的do-while循环代码：

import java.util.Scanner;

public class CoinFlip
{
    public static void main( String[] args )
    {
        Scanner keyboard = new Scanner(System.in);

        String coin, again;
        int flip, streak = 0;

        do
        {
            flip = 1 + (int)(Math.random()*2);

            if ( flip == 1 )
                coin = "HEADS";
            else
                coin = "TAILS";

            System.out.println( "You flip a coin and it is... " + coin );

            if ( flip == 1 )
            {
                streak++;
                System.out.println( "\tThat's " + streak + " in a row...." );
                System.out.print( "\tWould you like to flip again (y/n)? " );
                again = keyboard.next();
            }
            else
            {
                streak = 0;
                again = "n";
            }
        } while ( again.equals("y") );

        System.out.println( "Final score: " + streak );
    }
}

尝试从do-while循环执行while循环后的样子：

import java.util.Scanner;

public class CoinFlip2
{
    public static void main( String[] args )
    {
        Scanner keyboard = new Scanner(System.in);

        String coin, again;
        int flip, streak = 0;
        again = keyboard.next();
        //flip = 1 + (int) (Math.random()*2);

        while ( again.equals("y") )
        {
            flip = 1 + (int) (Math.random()*2);
            if ( flip == 1)
            {
                coin = "HEADS";
            }
            else
            {
                coin = "TAILS";
            System.out.println( "You flip a coin and it is..." + coin );
            }
            if ( flip == 1)
            {
                streak++;
                System.out.println("\tThat's " + streak + " in a row....");
                System.out.print( "\tWould you like to flip again (y/n)? ");
                //again = keyboard.next();
            }
            else
            {
                streak = 0;
                again = "n";
            }
            System.out.println( "Final score: " + streak);
        }
    }
}

代码编译没有问题，但运行后我看到空白输出。

Answer 1

这是因为您从未将again变量初始化为y，因此它永远不会匹配条件才能输入while

public static void main(String[] args) {
    Scanner keyboard = new Scanner(System.in);

    String coin, again = "y";
    int flip, streak = 0;
    // flip = 1 + (int) (Math.random()*2);

    while (again.equals("y")) {
        flip = 1 + (int) (Math.random() * 2);
        if (flip == 1) {
            coin = "HEADS";
        } else {
            coin = "TAILS";
            System.out.println("You flip a coin and it is..." + coin);
        }
        if (flip == 1) {
            streak++;
            System.out.println("\tThat's " + streak + " in a row....");
            System.out.print("\tWould you like to flip again (y/n)? ");
            again = keyboard.next();
            // again = keyboard.next();
        } else {
            streak = 0;
            again = "n";
        }
    }
    System.out.println("Final score: " + streak);
    keyboard.close();
}

输出：

That's 1 in a row....
Would you like to flip again (y/n)? y
You flip a coin and it is...TAILS
Final score: 0

Answer 2

使用again初始化您的"y"：

String coin, again;
int flip, streak = 0;
again = "y";
...

并在while循环中询问键盘输入：

if ( flip == 1)
{
    streak++;
    System.out.println("\tThat's " + streak + " in a row....");
    System.out.print( "\tWould you like to flip again (y/n)? ");
    again = keyboard.next();
}

尝试将do-while循环转换为while循环

2 个答案: