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();
}

在存储查找表的很小代价下，这个实现非常简单和快速。

 private static final char[] BYTE2HEX=(
    "000102030405060708090A0B0C0D0E0F"+
    "101112131415161718191A1B1C1D1E1F"+
    "202122232425262728292A2B2C2D2E2F"+
    "303132333435363738393A3B3C3D3E3F"+
    "404142434445464748494A4B4C4D4E4F"+
    "505152535455565758595A5B5C5D5E5F"+
    "606162636465666768696A6B6C6D6E6F"+
    "707172737475767778797A7B7C7D7E7F"+
    "808182838485868788898A8B8C8D8E8F"+
    "909192939495969798999A9B9C9D9E9F"+
    "A0A1A2A3A4A5A6A7A8A9AAABACADAEAF"+
    "B0B1B2B3B4B5B6B7B8B9BABBBCBDBEBF"+
    "C0C1C2C3C4C5C6C7C8C9CACBCCCDCECF"+
    "D0D1D2D3D4D5D6D7D8D9DADBDCDDDEDF"+
    "E0E1E2E3E4E5E6E7E8E9EAEBECEDEEEF"+
    "F0F1F2F3F4F5F6F7F8F9FAFBFCFDFEFF").toCharArray();
   ; 

  public static String getHexString(byte[] bytes) {
    final int len=bytes.length;
    final char[] chars=new char[len<<1];
    int hexIndex;
    int idx=0;
    int ofs=0;
    while (ofs<len) {
      hexIndex=(bytes[ofs++] & 0xFF)<<1;
      chars[idx++]=BYTE2HEX[hexIndex++];
      chars[idx++]=BYTE2HEX[hexIndex];
    }
    return new String(chars);
  }

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);
}

这是一个java.util。类似base64的实现，是不是很漂亮?

import java.util.Arrays;

public class Base16/* a.k.a. Hex */ {
    public static class Encoder{
        private static char[] toLowerHex={'0','1','2','3','4','5','6','7','8','9','a','b','c','d','e','f'};
        private static char[] toUpperHex={'0','1','2','3','4','5','6','7','8','9','A','B','C','D','E','F'};
        private boolean upper;
        public Encoder(boolean upper) {
            this.upper=upper;
        }
        public String encode(byte[] data){
            char[] value=new char[data.length*2];
            char[] toHex=upper?toUpperHex:toLowerHex;
            for(int i=0,j=0; i<data.length; i++){
                int octet=data[i]&0xFF;
                value[j++]=toHex[octet>>4];
                value[j++]=toHex[octet&0xF];
            }
            return new String(value);
        }
        static final Encoder LOWER_CASE=new Encoder(false);
        static final Encoder UPPER_CASE=new Encoder(true);
    }
    public static Encoder getEncoder(){
        return Encoder.LOWER_CASE;
    }
    public static Encoder getUpperEncoder(){
        return Encoder.UPPER_CASE;
    }

    public static class Decoder{
      private static int maxIndex=102;
      private static int[] toIndex;
      static {
        toIndex=new int[maxIndex+1];
        Arrays.fill(toIndex, -1);
        char[] chars={'0','1','2','3','4','5','6','7','8','9','A','B','C','D','E','F','a','b','c','d','e','f'};
        for(int i=0; i<chars.length; i++) {
          toIndex[(int)chars[i]]=i;
        }
      }
      public Decoder() {
      }
      public byte[] decode(String str) {
          char[] value=str.toCharArray();
          int start=0;
          if(value.length>2 && value[0]=='0' && (value[1]=='x' || value[1]=='X')) {
            start=2;
          }
          int byteLength=(value.length-start)/2; // ignore trailing odd char if exists
          byte[] data=new byte[byteLength];
          for(int i=start,j=0;i<value.length;i+=2,j++){
              int i1;
              int i2;
              char c1=value[i];
              char c2=value[i+1];
              if(c1>maxIndex || (i1=toIndex[(int)c1])<0 || c2>maxIndex || (i2=toIndex[(int)c2])<0) {
                throw new IllegalArgumentException("Invalid character at "+i);
              }
              data[j]=(byte)((i1<<4)+i2);
          }
          return data;
      }
      static final Decoder IGNORE_CASE=new Decoder();
  }
  public static Decoder getDecoder(){
      return Decoder.IGNORE_CASE;
  }
}

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();
}