如何使用while和for循环创建嵌套循环？

Question

我对循环有些新意，我需要在for循环之外插入一个while循环来计算空格，a，e，s和t。一旦用户键入短语，for循环将最后打印短语中空格，a，e，s和t的结果。我想创建一个while循环，允许你在输入“quit”时退出循环，并允许你键入一个新的短语，最终会得到更多的空格，a，e，s和t的结果。 。我已经尝试了while (phrase != "quit")但它没有用。很抱歉，如果有任何混淆，但是当您看到输入和输出时，您可能会理解。这是代码：

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;

        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 aest

Number of blank spaces: 2

Number of a's: 3
Number of e's: 3
Number of s's: 3
Number of t's: 3