Question

I’m having trouble in getting the binary. I do not know what’s wrong. The binary number always ends up in gibberish. Also some parts like the new int[31] thing was from HW but I can’t get around to make print the actual binary.

public class DectoBinary {
    public static void main(String[]args) {
        Scanner CONSOLE = new Scanner(System.in);
        System.out.print("Please enter a nonnegative integer: ");
        int value = CONSOLE.nextInt();
        while (value < 0) {
            System.out.print("number outside range.");
            System.out.print
                ("Please enter a nonnegative interger more than 0: ");
            value = CONSOLE.nextInt();
        }
        int[] intArray = new int[31];
        decimalToBinary(value, intArray);
        System.out.println(value + "" + intArray);
    }
    public static int[] decimalToBinary(int value, int[]intArray) {
        int i = 0;
        while (value != 0) {
            if (value % 2 == 1)
                intArray[i] = 1;

            else
                intArray[i] = 0;

            value /= 2;
            i++;
        }
        return intArray;
    }
}

Answer 1

I think the error is on this line:

System.out.println(value + "" + intArray);

You cannot print an array of integers like this: you should either convert it to string, or write a loop that prints the array digit by digit:

for (int i : inrArray) {
    System.out.print(intArray[i]);
}
System.out.println();

You do not need to pass in the output array as well: you can create it inside the function.

public static int[] decimalToBinary(int value) {
    int count = 1;
    int tmp = value;
    while (tmp != 0) {
        tmp /= 2;
        count++;
    }
    int[] intArray = new int[count];
    // Do the conversion here...
    return intArray;
}