CODEWITHSUNDEEP
javaarrays
monsterbasher
monsterbasher

Reputation: 65

Converting 4 different integers into a set length byte arrays

I'm trying to convert 4 integers from a text file and convert and assign them into a byte array of 26 bytes.

Ex. Text file contains numbers 1 8 113 4 and these four integers are to be placed in this exact sequence consecutively:

001 01000 0001110001 00000100

To further reiterate I want to have 4 bytes set and put an int into, so instead of outputting 2 like this 

10

I want it like

0010

Edit: Basically for the example above I just want 4 different byte arrays that have a set length of 3, 5, etc and want to insert an int into each array. Sorry for making it confusing.

Upvotes: 0

Views: 96

Answers (2)

Mr. Polywhirl
Mr. Polywhirl

Reputation: 48630

Using padding, you can achieve something like the following. String.format("%0{n}d", number) will not work here since the bitstring is not an integer and you can only prepend/append spaces to a string.

Output

0000001
0001000
1110001
0000100

Code

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

public class Test {
    public static void main(String[] args) {
        int[] values = { 1, 8, 113, 4 };
        int width = -getMaxWidth(values);

        for (int value : values) {
            System.out.println(prettyPrintBitString(value, width));
        }
    }

    public static String prettyPrintBitString(int value, int padding) {
        return pad(Integer.toBinaryString(value), '0', padding);
    }

    public static int getMaxWidth(int[] values) {
        return numberOfBits(Collections.max(toList(values)));
    }

    public static int numberOfBits(int value) {
        return (int) (Math.floor(Math.log(value) / Math.log(2)) + 1);
    }

    public static List<Integer> toList(int[] values) {
        List<Integer> list = new ArrayList<Integer>();
        for (int value : values) list.add(value);
        return list;
    }

    public static String pad(String str, char token, int count) {
        StringBuilder padded = new StringBuilder(str);
        if (count < 0) {
            while (padded.length() < -count) padded.insert(0, token);
        } else if (count > 0) {
            while (padded.length() < count) padded.append(token);
        }
        return padded.toString();
    }
}

Upvotes: 0

Elliott Frisch
Elliott Frisch

Reputation: 201447

If I understand your question, you could start by writing a function to pad a String with a leading character. Something like

public static String padString(String in, char padChar, int length) {
    StringBuilder sb = new StringBuilder(length);
    sb.append(in);
    for (int i = in.length(); i < length; i++) {
        sb.insert(0, padChar);
    }
    return sb.toString();
}

Then you could call Integer.toBinaryString(int) and pass the result to padString like

public static void main(String[] args) {
    System.out.println(padString(Integer.toBinaryString(2), '0', 4));
}

Output is (as requested)

0010

Upvotes: 2

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