这是另一个使用Streams的方法:

private static String toHexString(byte[] bytes) {
    return IntStream.range(0, bytes.length)
    .mapToObj(i -> String.format("%02X", bytes[i]))
    .collect(Collectors.joining());
}

最简单的解决方案，没有外部库，没有数字常量:

public static String byteArrayToHex(byte[] a) {
   StringBuilder sb = new StringBuilder(a.length * 2);
   for(byte b: a)
      sb.append(String.format("%02x", b));
   return sb.toString();
}

我通常使用以下方法进行debuf语句，但我不知道这是否是最好的方法

private static String digits = "0123456789abcdef";

public static String toHex(byte[] data){
    StringBuffer buf = new StringBuffer();
    for (int i = 0; i != data.length; i++)
    {
        int v = data[i] & 0xff;
        buf.append(digits.charAt(v >> 4));
        buf.append(digits.charAt(v & 0xf));
    }
    return buf.toString();
}

这是另一个使用Streams的方法:

private static String toHexString(byte[] bytes) {
    return IntStream.range(0, bytes.length)
    .mapToObj(i -> String.format("%02X", bytes[i]))
    .collect(Collectors.joining());
}

Apache Commons Codec库有一个Hex类用于完成这种类型的工作。

import org.apache.commons.codec.binary.Hex;

String foo = "I am a string";
byte[] bytes = foo.getBytes();
System.out.println( Hex.encodeHexString( bytes ) );

从这里的讨论，特别是这个答案，这是我目前使用的函数:

private static final char[] HEX_ARRAY = "0123456789ABCDEF".toCharArray();
public static String bytesToHex(byte[] bytes) {
    char[] hexChars = new char[bytes.length * 2];
    for (int j = 0; j < bytes.length; j++) {
        int v = bytes[j] & 0xFF;
        hexChars[j * 2] = HEX_ARRAY[v >>> 4];
        hexChars[j * 2 + 1] = HEX_ARRAY[v & 0x0F];
    }
    return new String(hexChars);
}

My own tiny benchmarks (a million bytes a thousand times, 256 bytes 10 million times) showed it to be much faster than any other alternative, about half the time on long arrays. Compared to the answer I took it from, switching to bitwise ops --- as suggested in the discussion --- cut about 20% off of the time for long arrays. (Edit: When I say it's faster than the alternatives, I mean the alternative code offered in the discussions. Performance is equivalent to Commons Codec, which uses very similar code.)

2k20版本，相对于Java 9的压缩字符串:

private static final byte[] HEX_ARRAY = "0123456789ABCDEF".getBytes(StandardCharsets.US_ASCII);
public static String bytesToHex(byte[] bytes) {
    byte[] hexChars = new byte[bytes.length * 2];
    for (int j = 0; j < bytes.length; j++) {
        int v = bytes[j] & 0xFF;
        hexChars[j * 2] = HEX_ARRAY[v >>> 4];
        hexChars[j * 2 + 1] = HEX_ARRAY[v & 0x0F];
    }
    return new String(hexChars, StandardCharsets.UTF_8);
}