我有一个字节数组充满十六进制数字和打印它的简单方式是相当没有意义的,因为有许多不可打印的元素。我需要的是精确的十六进制形式:3a5f771c


当前回答

HexFormat是在Java 17中加入的:

String hex = HexFormat.of().formatHex(array);

其他回答

@maybewecouldstealavan提出的解决方案的一个小变种,它让你在输出十六进制字符串中可视化地捆绑N个字节:

 final static char[] HEX_ARRAY = "0123456789ABCDEF".toCharArray();
 final static char BUNDLE_SEP = ' ';

public static String bytesToHexString(byte[] bytes, int bundleSize /*[bytes]*/]) {
        char[] hexChars = new char[(bytes.length * 2) + (bytes.length / bundleSize)];
        for (int j = 0, k = 1; j < bytes.length; j++, k++) {
                int v = bytes[j] & 0xFF;
                int start = (j * 2) + j/bundleSize;

                hexChars[start] = HEX_ARRAY[v >>> 4];
                hexChars[start + 1] = HEX_ARRAY[v & 0x0F];

                if ((k % bundleSize) == 0) {
                        hexChars[start + 2] = BUNDLE_SEP;
                }   
        }   
        return new String(hexChars).trim();    
}

那就是:

bytesToHexString("..DOOM..".toCharArray().getBytes(), 2);
2E2E 444F 4F4D 2E2E

bytesToHexString("..DOOM..".toCharArray().getBytes(), 4);
2E2E444F 4F4D2E2E

HexFormat是在Java 17中加入的:

String hex = HexFormat.of().formatHex(array);

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);
}

//移位字节更有效 //你也可以用这个

public static String getHexString (String s) 
{
    byte[] buf = s.getBytes();

    StringBuffer sb = new StringBuffer();

    for (byte b:buf)
    {
        sb.append(String.format("%x", b));
    }


        return sb.toString();
}

好的,有很多方法可以做到这一点,但如果你决定使用一个库,我建议在你的项目中看看是否已经在一个库中实现了一些东西,而这个库已经是你项目的一部分,然后再添加一个新的库来做到这一点。例如,如果你还没有

org.apache.commons.codec.binary.Hex

也许你有…

org.apache.xerces.impl.dv.util.HexBin