making a integer using loop

Question

import java.io.IOException;

public class Main {

    public static void main(String[] args) throws IOException {
        int number = 0;
        int keyValue = System.in.read();
        keyValue = keyValue - 48;
        number = number * 10 + keyValue;
        System.out.println(number);

        while(true) {
            keyValue = System.in.read();
            keyValue = keyValue - 48;
            number = number * 10 + keyValue;
            System.out.println(number);
            if(keyValue == 120) {
                number = number - 120;
                System.out.println(number);
                break;
            }
        }

        }

    }

I want to get integer value from the keyboard. subtracting 48 is gonna make ASCII Code to be a value that I entered on a keyboard.

I don't only want to do this in first digit, but make a integer whatever I enter on a keyboard, using while loop and if condition.

What do you think is the problem? please help me.

"subtracting 48" subtracting '0' is clearer, and equivalent. — Andy Turner
– Andy Turner, Commented Mar 12, 2019 at 8:33
the problem is you are vague about what your problem is. also, you risk an endless loop with your while(true). if ( keyvalue == 120 ) never evaluates to true, well ... — Stultuske
– Stultuske, Commented Mar 12, 2019 at 8:33
System.in buffers input. System.in.read() won't return anything until it is flushed, e.g. by pressing enter or closing the stream. — Andy Turner
– Andy Turner, Commented Mar 12, 2019 at 8:34

Joop Eggen · Accepted Answer · 2019-03-12 09:25:57Z

1

Your code had the break condition too late: number already messed up, multiplied by 10, added the 120 - 48. Theoriginal key value - 48 == 120`.

But I think you wanted to test on the letter 'x'.

    while (true) {
        keyValue = System.in.read();
        if (keyValue == 'x') {
            System.out.println(number);
            break;
        }
        keyValue = keyValue - '0';
        number = number * 10 + keyValue;
        System.out.println(number);
    }

However the console System.in is line buffered, you will not get input before Enter was pressed.

answered Mar 12, 2019 at 9:25

Joop Eggen

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Comments

Stanimir Iankov · Accepted Answer · 2019-03-12 09:06:22Z

I don't know if that´s what you are looking for, but if you are trying to create a ASCII to int by substracting the 48 value here is the correct code:

    public static void main(String[] args) throws IOException {
    Scanner sc = new Scanner(System.in);
    int number = 0;
    System.out.println("Please enter your ASCII code!");
    int keyValue = sc.nextInt();
    keyValue = keyValue - 48;
    number = number * 10 + keyValue;
    System.out.println(number);

    while (true) {
        number = 0;
        System.out.println("Please enter your ASCII code!");
        keyValue = sc.nextInt();
        keyValue = keyValue - 48;
        number = number * 10 + keyValue;
        System.out.println(number);
        if (keyValue == 120) {
            number = number - 120;
            System.out.println(number);
            break;
        }
    }
}

Cases:

When you enter 48 you get 0, with 49 you get 1 ... when you enter 168 the loop brokes and the program ends.

I hope that's helpfull for you.

Rajesh Nair · Accepted Answer · 2019-03-12 09:42:48Z

Do you want it to be printed one after other or in a single line. If you want it to be in a single line . Hope you get help from the code snippet below :-

public class Main {

    public static void main(String[] args) throws IOException {
        int number = 0;
        int keyValue = 0;
        /*int keyValue = System.in.read();
        keyValue = keyValue - 48;
        number = number * 10 + keyValue;
        System.out.println(number);*/

        while (true) {
            number =0;
            keyValue = System.in.read();
            keyValue = keyValue - 48;
            if(keyValue == -38){
                System.out.println();
            }else {
                if (keyValue < 0 || keyValue > 122) {
                    System.out.println(" BREAK "+keyValue);
                    break;
                }
                number = number * 10 + keyValue;
                System.out.print(number);
            }
        }

    }

}

Output :-

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