如何围绕允许用户退出循环的 for 循环创建一个 while 循环？

Question

我是循环的新手，我已经编写了一个 for 循环，提示用户输入一个短语，for 循环打印出有多少空格，a's，e's ，s's 和 t's。我需要做一个while循环，允许用户输入“quit”来退出循环。我也是学习开关打印字母的新手。我已经尝试使用我的代码来修复我的错误（持续循环或没有结果）超过一周。下面是我的代码，在此先感谢您。

import java.util.Scanner;
public  class Count
{

public static void main (String[] args)
{

    Scanner scan = new Scanner (System.in);
    String phrase;    // a string of characters
    int countBlank;   // the number of blanks (spaces) in the phrase 
    int i = 0;
    char ch;          // an individual character in the string
    String quit = "quit";
    System.out.println ();
    System.out.println ("Character Counter");
    System.out.println ();

    System.out.print ("Enter a sentence or phrase (quit to quit): ");
    phrase = scan.nextLine(); // read input Scanner  
    int length = phrase.length();       // the length of the phrase

    countBlank = 0;
    int countA = 0;
    int countE = 0;
    int countS = 0;
    int countT = 0;

    //I am not sure how to set up the start of the while loop
    //while (!phrase.equals("quit")){
    //while (phrase != "quit"){

    for (i = 0; i < length; i++){
        ch = phrase.charAt(i);
        if (ch == (' '))
            countBlank++;
        switch (ch)
        {
        case 'a': case 'A':  countA++; break;
        case 'e': case 'E':  countE++; break;
        case 's': case 'S':  countS++; break;
        case 't': case 'T':  countT++; break;       
        }
    }
    System.out.println ();
    System.out.println ("Number of blank spaces: " + countBlank);
    System.out.println ();
    System.out.println ("Number of a's: " +countA);
    System.out.println ("Number of e's: " +countE);
    System.out.println ("Number of s's: " +countS);
    System.out.println ("Number of t's: " +countT);
    }
}

输出：

Character Counter

Enter a sentence or phrase (quit to quit): AEST aest

Number of blank spaces: 1

Number of a's: 2
Number of e's: 2
Number of s's: 2
Number of t's: 2

Answer 1

您在正确的轨道上，但您确实需要在该过程完成后再次阅读该短语以使 while 循环正常工作。否则，将是无限循环。 以下是我所做的一些更改：

 while (!phrase.equals("quit")){

        for (i = 0; i < length; i++){
            ch = phrase.charAt(i);
            if (ch == (' '))
                countBlank++;
            switch (ch)
            {
            case 'a': case 'A':  countA++; break;
            case 'e': case 'E':  countE++; break;
            case 's': case 'S':  countS++; break;
            case 't': case 'T':  countT++; break;       
            }
        }
        System.out.println ();
        System.out.println ("Number of blank spaces: " + countBlank);
        System.out.println ();
        System.out.println ("Number of a's: " +countA);
        System.out.println ("Number of e's: " +countE);
        System.out.println ("Number of s's: " +countS);
        System.out.println ("Number of t's: " +countT);
        phrase =scan.nextLine(); //read next phrase from user to continue.
        }

Answer 2

在phrase = scan.nextLine(); 之后使用它

if(phrase.equalsIgnoreCase("quit")){ return; }