Multiple methods for Java to convert byte arrays into hexadecimal

In many cases, we need to convert byte arrays into hexadecimal strings for storage, especially in many encryption scenarios, such as saving keys. In addition to writing data to a file or writing data to a database in binary format, the byte array cannot be directly converted to a string because \ 0 exists at the end of the string. Of course, there must be other reasons.

The following solutions are used in Java:

Solution 1: The BigInteger method should be the simplest solution.

/*** Use the signature helper class to convert the String byte array * @ param str * @ return */public static byte [] md5 (String str) {byte [] digest = null; try {MessageDigest md = MessageDigest. getInstance ("md5"); return digest = md. digest (str. getBytes ();} catch (NoSuchAlgorithmException e) {e. printStackTrace ();} return null;}/*** method 1 ** @ param bytes * @ return */public static String bytes2hex01 (byte [] bytes) {/*** for the explanation of the first parameter, remember to set it to 1 * signum of the number (-1 for negative, 0 for zero, 1 for positive ). */BigInteger bigInteger = new BigInteger (1, bytes); return bigInteger. toString (16 );}

Solution 2: perform operations on each byte and 0xFF, convert it to hexadecimal, and then convert it to hexadecimal by using Integer.

/*** Method 2 ** @ param bytes * @ return */public static String bytes2hex02 (byte [] bytes) {StringBuilder sb = new StringBuilder (); String tmp = null; for (byte B: bytes) {// calculate each byte and 0xFF, convert it to hexadecimal, and then convert it to hexadecimal tmp = Integer by Integer. toHexString (0xFF & B); if (tmp. length () = 1) // each byte is 8, converted to a hexadecimal flag, two hexadecimal bits {tmp = "0" + tmp;} sb. append (tmp);} return sb. toString ();}

Solution 3: retrieve the four-byte and four-byte values, and then obtain the values from the 10th to 0-15 respectively. Then, use a string array to complete the process perfectly. The third method is recommended for understanding the conversion.

/*** Method 3 ** @ param bytes * @ return */public static String bytes2hex03 (byte [] bytes) {final String HEX = "0123456789 abcdef "; stringBuilder sb = new StringBuilder (bytes. length * 2); for (byte B: bytes) {// retrieves the 4-bit high of this byte, and then computes it with 0x0f to obtain a data between 0 and 15, through HEX. charAt (0-15) is a hexadecimal number sb. append (HEX. charAt (B> 4) & 0x0f); // retrieves the low position of this byte, and returns the data between 0 and 15 through HEX. charAt (0-15) is a hexadecimal number sb. append (HEX. charAt (B & 0x0f);} return sb. toString ();}