初级编码器 (Java) - 验证字符串输入并在输入正确输入后结束循环

Question

The idea with this question is that the user knows to input the sentence "Robin came to Montreal, Canada in 2009.". From there, the code should spit back "Robin stays in Montreal, for 11 years. Montreal is in Canada. Please enter the input sentence (press q to exit):".

I've managed to get a loop going so that as long as the user is inputting the sentence correctly the program will also spit back the correct phrase. The part that I'm struggling with is ending the loop - getting "q" to terminate the program. Instead I get an error. Please let me know what I can do.

import java.util.Scanner;
import java.util.regex.Pattern;
import java.util.regex.Matcher;

public class MiniTranslator {

public static void main(String[] args) {
    
    Scanner scan = new Scanner(System.in);
    String sentence;
    
    do {
        System.out.println("Please enter the input sentence (press q to exit)");
        sentence = scan.nextLine();
        int i = sentence.indexOf(' ');
        String word = sentence.substring(0, i);
        String sentence2 = sentence.substring(i + 9, sentence.length());
        int j = sentence2.indexOf(' ');
        String word2 = sentence2.substring(0, j);
        Matcher matcher = Pattern.compile("\\d+").matcher(sentence);
        matcher.find();
        int k = Integer.valueOf(matcher.group());
        String sentence3 = sentence2.substring(j + 1, sentence2.length());
        int l = sentence3.indexOf(' ');
        String word3 = sentence3.substring(0, l);
        System.out.println(word + " stays in " + word2 + "  for " + (2020 - k) + " years. " + word2 + " is in " + word3 + ".");
        System.out.println(" ");
        
    } while (!"q".equals(sentence));
    
    do {
        System.out.println("Thanks for using the translator program.");
        System.out.println(" ");
        System.out.println("The program is now terminated");
    } while ("q".equals(sentence));

Answer 1

First of all you should probably share you error message so community members can better understand your problem. But n.netheless your code should be while(.sentence.equals("q")) , since you basically want to call the.equals() method, and you need to create a type String Object for that. "q" is just a String expression that can be passed into the.equals() method.

Answer 2

The part that I'm struggling with is ending the loop - getting "q" to terminate the program. Instead I get an error. Please let me know what I can do.

I have solved the part where you were struggling, but your program logic is incorrect and you need to work on that. For that learn aboutString class and its functions.

Anyway, here is your program press q to exit code

    Scanner scan = new Scanner(System.in);
String sentence;
boolean doAgain = true;
do 
{
    System.out.println("Please enter the input sentence (press q to exit)");
    sentence = scan.nextLine();
    if("q".equals(sentence))
    {
        doAgain = false;
    }
    else
    {
        //your program logic in here
        
        int i = sentence.indexOf(' ');
        String word = sentence.substring(0, i);
        String sentence2 = sentence.substring(i + 9, sentence.length());
        int j = sentence2.indexOf(' ');
        String word2 = sentence2.substring(0, j);
        Matcher matcher = Pattern.compile("\\d+").matcher(sentence);
        matcher.find();
        int k = Integer.valueOf(matcher.group());
        String sentence3 = sentence2.substring(j + 1, sentence2.length());
        int l = sentence3.indexOf(' ');
        String word3 = sentence3.substring(0, l);
        System.out.println(word + " stays in " + word2 + "  for " + (2020 - k) + " years. " + word2 + " is in " + word3 + ".");
        System.out.println(" ");
        
    }
} while (doAgain);

System.out.println("Thanks for using the translator program.");
System.out.println(" ");
System.out.println("The program is now terminated");