md5加密后字母分别以大写字母和小写字母显示

//以小写字母方式显示md5加密后的字符串

public static String md5(String str){
try {
MessageDigest md = MessageDigest.getInstance("MD5");
md.update(str.getBytes());
byte[] b = md.digest();
StringBuffer sb = new StringBuffer();
for (int i = 0; i < b.length; i++) {
int v = (int) b[i];
v = v < 0 ? 0x100 + v : v;
String cc = Integer.toHexString(v);
if (cc.length() == 1)
sb.append('0');
sb.append(cc);
}
return sb.toString();
}
catch (Exception e) {
}
return "";
}

//以大写字母方式显示md5加密后的字符串

public static String md5Capital(String s){
char hexDigits[] = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F' };
try {
byte[] strTemp = s.getBytes();
//使用MD5创建MessageDigest对象
MessageDigest mdTemp = MessageDigest.getInstance("MD5");
mdTemp.update(strTemp);
byte[] md = mdTemp.digest();
int j = md.length;
char str[] = new char[j * 2];
int k = 0;
for (int i = 0; i < j; i++) {
byte b = md[i];
//System.out.println((int)b);
//将没个数(int)b进行双字节加密
str[k++] = hexDigits[b >> 4 & 0xf];
str[k++] = hexDigits[b & 0xf];
}
return new String(str);
} catch (Exception e) {return null;}
}2、Java生成任意位数的字母数字组合随机数
//生成随机数字和字母, length为位数

public String getStringRandom(int length) {
String val = “”;
Random random = new Random();
// 参数length，表示生成几位随机数
for (int i = 0; i < length; i++) {
String charOrNum = random.nextInt(2) % 2 == 0 ? “char” : “num”;
// 输出字母还是数字
if (“char”.equalsIgnoreCase(charOrNum)) {
// 输出是大写字母还是小写字母
int temp = random.nextInt(2) % 2 == 0 ? 65 : 97;
val += (char) (random.nextInt(26) + temp);
} else if (“num”.equalsIgnoreCase(charOrNum)) {
val += String.valueOf(random.nextInt(10));
}
}
return val;
}