Question

我正在将它转换为Java程序：

$ java SpaceTravel
Welcome to the SpaceTravel agency
What do you want do? [h for help]
a
Unknown command. Type h for help
What do you want do? [h for help]
h
h: print this help screen
q: quit the program
What do you want do? [h for help]
q
Bye bye!

现在问题是我的程序似乎在第二个do while循环中做了无限循环，无论我选择了什么，我尝试了很多算法和钢铁对我不起作用。这是我的代码：

package gesitionEleve;

import java.util.Scanner;


public class SpaceTravel {

    public static void main(String[] args) {

        System.out.print("Welcom to the SpaceTravel Agency\n");


        int lafin = 0;

        while (lafin != 1) {

            int taill;
            do {
                System.out.print("What do you want to do [h for help] : ");
                Scanner sc = new Scanner(System.in);
                String test = sc.nextLine();
                taill = test.length();
            } while(taill == 0);

            char choix = 0;

            String test;
            if (choix != 'h') {

                do {
                    System.out.print("\nUknown command. Type h for help ");
                    System.out.print("\nWhat do you want to do : ");
                    Scanner sc1 = new Scanner(System.in);
                    test = sc1.nextLine();
                    choix = test.charAt(0);
                } while(choix == 'h');

            }

            System.out.print("\nh : print this help page ");
            System.out.print("\nq : quite the program ");                       

            do {
                Scanner sc1 = new Scanner(System.in);
                        test = sc1.nextLine();
                        choix = test.charAt(0);

                        switch(choix) {
                            case 'h' : 
                            System.out.print("\nh : print this help page ");
                            System.out.print("\nq : quite the program ");
                            case 'q' : 
                            System.out.print("Bye bye");
                            lafin++;
                        }
            } while (choix == 'q' || choix == 'h');
        }

    } 

}

Answer 1

以下计划适合您的需求：

import java.util.Scanner;

public class SpaceTravel
{
      public static void main(String[] args) {

        System.out.print("Welcome to the SpaceTravel Agency\n");

        String str; //To avoid exception when user enters just an enter

        while (true) { //infinite loop

          char choix; //for getting a character

            System.out.print("What do you want to do [h for help] : ");
            Scanner sc = new Scanner(System.in);
            str=sc.nextLine();  //get input
            if(str.length()!=1) //If no characters or more than one character is entered,
            {
              System.out.println("Invalid Choice");
              continue;
            }
            choix=str.charAt(0); //get char from str

          if(choix=='q') //if char is q,break out of the while loop
              break;  
          if (choix != 'h') { //if char is not h,print invalid input and continue the loop

              System.out.println("\nUnknown command. Type h for help ");
              continue;

          }

          System.out.print("\nh : print this help page ");
          System.out.print("\nq : quit the program ");           

        }

      } 
}

Answer 2

你得到了循环的条件。

如果你想在输入'h'时离开循环，它应该是：

            do {
                System.out.print("\nUknown command. Type h for help ");
                System.out.print("\nWhat do you want to do : ");
                Scanner sc1 = new Scanner(System.in);
                test = sc1.nextLine();
                choix = test.charAt(0);
            } while(choix != 'h');

目前，只要输入“h”，您就会停留在循环中。

您还应注意，如果用户在不键入任何字符的情况下按Enter键，test.charAt(0)将抛出异常。

我正在尝试用java解决算法，我发现了一些问题

2 个答案: