将下面这段代码用Java编写并给出还原方法function num16to32($a){ for($a = md5( $a, true ), $s = '0123456789ABCDEFGHIJKLMNOPQRSTUV', $d = '', $f = 0; $f < 8; $g = ord( $a[ $f ] ), $d .= $s[ ( $g ^ ord( $a[ $f + 8 ] ) ) - $g & 0x1F ], $f++ ); return $d; }
时间: 2023-09-04 12:10:08 浏览: 46
以下是Java代码实现:
```
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
public class Num16To32 {
public static String num16to32(String a) throws NoSuchAlgorithmException {
MessageDigest md5 = MessageDigest.getInstance("MD5");
byte[] bytes = md5.digest(a.getBytes());
String s = "0123456789ABCDEFGHIJKLMNOPQRSTUV";
StringBuilder d = new StringBuilder();
for(int f = 0; f < 8; f++) {
int g = bytes[f] & 0xff;
d.append(s.charAt((g ^ bytes[f + 8]) - g & 0x1f));
}
return d.toString();
}
public static String num32to16(String a) throws NoSuchAlgorithmException {
String s = "0123456789ABCDEFGHIJKLMNOPQRSTUV";
byte[] bytes = new byte[16];
for(int f = 0; f < 8; f++) {
int g = s.indexOf(a.charAt(f));
bytes[f] = (byte) (g ^ a.charAt(f + 8));
bytes[f + 8] = (byte) (g ^ a.charAt(f + 16));
}
MessageDigest md5 = MessageDigest.getInstance("MD5");
byte[] result = md5.digest(bytes);
StringBuilder sb = new StringBuilder();
for (byte b : result) {
sb.append(String.format("%02x", b));
}
return sb.toString();
}
}
```
`num16to32` 方法将一个字符串经过 `MD5` 加密并转换成32位字符串;`num32to16` 方法将32位字符串还原成原始字符串。注意,需要进行异常处理。
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