为什么我的Bit String to Hex String代码无法打印结果？

Question

I am trying to print the result of a bit string to hex string conversion but it prints nothing. In other words 000110011101 should print "19d" are my temp variables the issue?

Thanks in advance for any assistance, this is my code:

public static void BinaryToHex() {
        Scanner scanner = new Scanner(System.in);
        String bitString = "";
        String hexString = "";

    String[] hex = { "0", "1", "2", "3", "4", "5", "6", "7", "8", "9", "A", "B", "C",
            "D", "E", "F" };
    String[] binary = { "0000", "0001", "0010", "0011", "0100", "0101", "0110",
            "0111", "1000", "1001", "1010", "1011", "1100", "1101", "1110", "1111" };

    System.out.println("Enter a bit string: ");
    bitString = scanner.next();

    for (int i = 0; i < bitString.length(); i++) {
        char temp = bitString.charAt(i);
        String temp2 = "" + temp + "";
        for (int j = 0; j < binary.length; j++) {
            if (temp2.equalsIgnoreCase(binary[j])) {
                hexString = hexString + hex[j];
            }
        }
    }

    System.out.print("The equivalent hex string is ");
    System.out.println(hexString);
}

Answer 1

for (int i = 0; i < bitString.length(); i++) {
        char temp = bitString.charAt(i);
        String temp2 = "" + temp + "";
        for (int j = 0; j < binary.length; j++) {
            if (temp2.equalsIgnoreCase(binary[j])) {
                hexString = hexString + hex[j];
            }
        }
    }

In this loop you are trying to take one character of a bitString at a time and compare it with the input of binary[] array which has all input of length 4 . So basically you are trying to comparing 1 length element with 4 length element which is never going to be true.

Therefore HexString will never get changed and it will print same as you have initialized it.So you are getting nothing while executing the code.

You can have a substring of bitString having 4 lengths and store it in temp2 then this code will work and for every 4 bits there is a HexCharacter so you can't make 1 bit number into binary number.

So as per your logic , bitString length should be of multiples of 4 otherwise it won't give corresponding hex character from hex array.

Replace the for loop in your code with this.

if(bitString.length()%4!=0)
    System.out.println("Please Enter Valid Input.");
else
{
    for (int i = 0; i < bitString.length()/4; i++) 
    {
        String temp2 = bitString.substring(4*i,4*(i+1));
        for (int j = 0; j < binary.length; j++)
            {
            if (temp2.equalsIgnoreCase(binary[j]))
                {
                hexString = hexString + hex[j];
            }
        }
    }
    System.out.print("The equivalent hex string is ");
    System.out.println(hexString);
}

Answer 2

Your temp2 String is re-defined every time inside the outer for-loop, which loops through the char s of the input String. This means that temp2 never actually contains more than a single symbol (because it gets reset every iteration of the loop), and therefore can never equal any of the Strings in the binary array.

You'll want to define the temp2 String once first as String temp2 = "" outside the loop, and then inside the loop append temp to it.