每个byte为8位，用16进制表示需要2个16进制位
比如：
半个byte：(二进制1111) == (十进制15) == (十六进制f)
一个byte：(二进制11111111) == (十进制255) == (十六进制ff)
import javax.xml.bind.DatatypeConverter;
import java.io.UnsupportedEncodingException;
import java.math.BigInteger;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.Arrays;
public class Test {
public static void main(String[] args) {
MessageDigest messageDigest = null;
try {
String str = "测试字符串";
messageDigest = MessageDigest.getInstance("SHA1");
messageDigest.update(str.getBytes("UTF-8"));
byte bytes[] = messageDigest.digest();
BigInteger bigInteger = new BigInteger(1, bytes);
System.out.println(bigInteger.toString(16));
String strHexBytes = DatatypeConverter.printHexBinary(bytes);
System.out.println(strHexBytes);
System.out.println(bytes2hex(bytes));
} catch (NoSuchAlgorithmException | UnsupportedEncodingException e) {
e.printStackTrace();
}
}
public static String bytes2hex(byte[] bytes) {
StringBuilder sb = new StringBuilder();
String tmp = null;
for (byte b : bytes) {
// 将每个字节与0xFF进行与运算，然后转化为10进制，然后借助于Integer再转化为16进制
tmp = Integer.toHexString(0xFF & b);
if (tmp.length() == 1) {
tmp = "0" + tmp;
}
sb.append(tmp);
}
return sb.toString();
}
}
