程序从文件中读取字节并转换为十六进制

Question

import java.io.*;

public class foo {

    public static void main(String[] args) {

        try {
            DataInputStream input = new DataInputStream(new FileInputStream(
                    "data.dat"));

            while (input.available() > 0) {

                String hex = Integer.toHexString(input.readByte()); //I think this is where the problem is

                System.out.print(hex + ' ');

            }

        } catch (IOException e) {
        }

    }
}

Output-

ffffff89 50 4e 47 d a 1a a 0 0 0 d 49 48 44 52 0 0 0... (continues)

The output is mostly correct. I can't figure out where these ffffffs are coming in my output. And also single single characters are missing their 0. eg. d should be displayed as 0D

Answer 1

input.readByte() returns a signed byte; when the highest bit of that byte is 1, it is interpreted as a negative number, and Integer.toString sign-extends it to an int.

Instead of Integer.toString , use String.format("%02x", input.readByte() & 0xFF) , which will interpret the byte as unsigned and force exactly two hexadecimal digits to be used.