How to use System.in.read() in java?

Question

I need to input and load some chars in a boolean 2-D array. If the char is X , mark the array element as true ; else if the char is . , mark the array element as false.

Here is my design:

boolean[][] Array = new boolean[2][2];

for (int i = 0; i < 2; i++) {  
   for (int j = 0; j < 2; j++) {
        if (System.in.read() == '.') {
            Array[i][j] = false;
        } else if (System.in.read() == 'X') {
            Array[i][j] = true;
        }
    }
}

And, for example, if I type in .... or XXXX , it does not produce the correct result. Also for other input the result is not correct.

So how to deal with this?

Answer 1

You are reading a character a second time in the loop if the first character is not a '.' .

You should only read one character per loop. Save the character in a variable before your if statement, and then compare the variable to '.' and 'X' in turn.

Answer 2

You shouldn't call the read() function in each if statement. Call it one time and store it in a variable so you don't keep reading through the input. That could be one thing messing up your function. Another is how you are comparing char s with the == operator. Should use char.equals method for character comparison. Put a couple breakpoints in and see what values are being sent through to debug. Maybe try something like the following:

boolean[][] Array= new boolean[2][2];

for (int i = 0; i < 2; i++) {  
  for (int j = 0; j < 2; j++) {
        Character input = (char)System.in.read();
        if (input.equals('.')) {
            Array[i][j] = false;
        } else if (input.equals('X')) {
            Array[i][j] = true;
        }
    }
}