使用Java将字节数组转成16进制形式的代码实现

public class ASMDemoEntity {
    private int intNum = 10;
    private static final String staticString = "hello world";

    public void fun() {
        System.out.println("I am fun");
    }

    public int add(int a, int b) {
        return a + b;
    }

    public static void main(String[] args) {
        System.out.println("a+b = " + new ASMDemoEntity().add(1, 2));
        new ASMDemoEntity().fun();
    }
}

public enum HexFormat {
    // 无分隔符分别展示0，8，16，32列
    FORMAT_HEX_0("", 0),
    FORMAT_HEX_8("", 8),
    FORMAT_HEX_16("", 16),
    FORMAT_HEX_32("", 32),

    // 带空格分隔符分别展示0，8，16，32列
    FORMAT_HEX_SPACE__0(" ", 0),
    FORMAT_HEX_SPACE_8(" ", 8),
    FORMAT_HEX_SPACE_16(" ", 16),
    FORMAT_HEX_SPACE_32(" ", 32);

    public final String separator; // 分隔符
    public final int column; // 展示几列

    HexFormat(String separator, int column) {
        this.separator = separator;
        this.column = column;
    }
}

public class FileUtil {
    public static String getFilePath(String relativePath){
        URL resource = FileUtil.class.getResource("/");
        String dir = resource == null? "" : resource.getPath();
        return dir + relativePath;
    }
    public static byte[] readBytes(String filePath){
        File file = new File(filePath);
        if(!file.exists()){
            throw new IllegalArgumentException(filePath + "not exist");
        }
        InputStream in = null;
        try {
            in = Files.newInputStream(file.toPath());
            in = new BufferedInputStream(in);
            ByteArrayOutputStream bao = new ByteArrayOutputStream();
            IOUtil.copy(in,bao);
            return bao.toByteArray();
        } catch (IOException e) {
            e.printStackTrace();
        }finally {
            IOUtil.closeIO(in);
        }
        return null;
    }
}

public class IOUtil {
    private static final int EOF = -1;
    private static final int BUFFER_SIZE = 1024 * 4;

    public static long copy(final InputStream input,
                            final OutputStream output) throws IOException {
        long count = 0;
        int n;
        byte[] buffer = new byte[BUFFER_SIZE];
        while (EOF != (n = input.read(buffer))) {
            output.write(buffer, 0, n);
            count += n;
        }

        return count;
    }

    public static void closeIO(final Closeable closeable) {
        if(closeable != null){
            try {
                closeable.close();
            } catch (IOException ignored) {
            }
        }

    }
}

public class HexUtil {
    public static String hexFormat(byte[] bytes,HexFormat format){
        String separator = format.separator;
        int column = format.column;
        return hexFormat(bytes,separator,column);
    }

    private static String hexFormat(byte[] bytes, String separator, int column) {
        if(bytes == null || bytes.length < 1) {
            return "";
        }

        StringBuilder sb = new StringBuilder();
        Formatter fm = new Formatter(sb);

        int length = bytes.length;
        for (int i = 0; i < length; i++) {
            int val = bytes[i] & 0xFF;
            fm.format("%02X",val);
            if(column > 0 && (i+1) % column == 0){
                fm.format("%n");
            }else{
                fm.format("%s",separator);
            }
        }

        return sb.toString();
    }
}

public class HexFormatMain {
    public static void main(String[] args) {
        String relativePath = "org/example/entity/ASMDemoEntity.class";
        String filePath = FileUtil.getFilePath(relativePath);
        System.out.println("file path: " + filePath);
        byte[] bytes = FileUtil.readBytes(filePath);
        String hex = HexUtil.hexFormat(bytes, HexFormat.FORMAT_HEX_SPACE_32);
        System.out.println("class文件的16进制： ");
        System.out.println(hex);
    }
}