打印输入中的每个字符

Question

I've been teaching myself Java with http://www.cs.princeton.edu/courses/archive/spr15/cos126/lectures.html as a reference. They have a library called algs4 and it has several classes including StdIn, which I'm trying to implement below.

import edu.princeton.cs.algs4.StdIn;
import edu.princeton.cs.algs4.StdOut;

public class Tired
{  
    public static void main(String[] args)
    {
        //I thought this while statement will ask for an input 
        //and if an input is provided, it would spell out each character
        while (!StdIn.hasNextChar()) {

             StdOut.print(1);  //seeing if it gets past the while conditional
            char c = StdIn.readChar();
            StdOut.print(c);
        }       
    }    
}


//This is from StdIn class. It has a method called hasNextChar() as shown below.  
/*
     public static boolean hasNextChar() {
        scanner.useDelimiter(EMPTY_PATTERN);
        boolean result = scanner.hasNext();
        scanner.useDelimiter(WHITESPACE_PATTERN);
        return result;
    }
 */

If i run the code, it does ask for an input, but regardless of what i type in, nothing happens and nothing gets printed out.

I see that even StdOut.print(1); doesnt get printed out, so for some reason, it just gets stuck on while

Answer 1

It looks like the issue is with the condition for your while loop:

!StdIn.hasNextChar()

This says to continue as long as there isn't a next char. But you want to continue while there is one, so get rid of that ! and you should be good.

Answer 2

Here is some alternative code that works similarly. Not the best coding but works.

import java.util.Scanner;

public class test{

    static Scanner StdIn = new Scanner(System.in);
    static String input;

    public static void main(String[] args){

        while(true){
            if(input.charAt(0) == '!'){ // use ! to break the loop
                break;
            }else{
                input = StdIn.next();  // store your input
                System.out.println(input); // look at your input
            }
        }
    }   
}