java的长字符串转化为短字符串
public class CustomEncrypt{
public static void main( String[] args ) {
/*
* c#给的正确测试⽤例: id=>mid
* 991135225=>001B4Lk5
* 981411932=>001A5Vj6
* 988914785=>001ABp8R
* 97879005=>0009x3GJ
*
* 981612013=>001A6Lmd
*
* 97949621=>0009xm3H
*
* 97919383=>0009xebZ
*
* 984113004=>001AhfYM
*
* 986013809=>001ApesV
*
* 97416233=>0009v7iF
*
* 9090103=>C8Kz
*
* 9194277359=>00ePhWJF
* 96521442=>0009rmwy
*/
String ids = "9734249,981411932,988914785,97879005,981612013,97949621,97919383,984113004,986013809,97416233,9090103,9194277359,96521442";
for(String id : ids.split( "," )){
String mid = idToMid(id);
System.out.println("mid:"+mid);
System.out.println("id:"+midToId(mid));
}
}
// / <summary>
// / The str62keys
// / </summary>
private static String str62keys = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
// / <summary>
// / 将Mid转换为Id
// / </summary>
// / <param name="str62">The STR62.</param>
// / <returns>System.String.</returns>
public static String midToId( String str62 ) {
String id = "";
// 从最后往前以4字节为⼀组读取字符
for ( int i = str62.length( ) - 4; i > -4; i = i - 4 ) {
int offset = i < 0 ? 0 : i;
int len = i < 0 ? str62.length( ) % 4 : 4;
long encode = encode62ToInt( left( str62, offset, len ) );
String str = String.valueOf( encode );
if ( offset > 0 )
str = leftPad( str, 7, '0' ); // 若不是第⼀组，则不⾜7位补0
id = str + id;
}
return id;
}
// / <summary>
// / 将Id转制为Mid
// / </summary>
// / <param name="mid">The mid.</param>
// / <returns>System.String.</returns>
public static String idToMid( String mid ) {
// long int_mid = long.Parse(mid);
String result = "";
for ( int i = mid.length( ) - 7; i > -7; i -= 7 ) {
int offset1 = ( i < 0 ) ? 0 : i;
int offset2 = i + 7;
String num = intToEnode62( left( mid, offset1, offset2 - offset1 ) );
result = num + result;
}
return result;
// / <summary>
// / Ints to enode62.
// / </summary>
// / <param name="mid">The mid.</param>
// / <returns>System.String.</returns>
private static String intToEnode62( String mid ) {
long int_mid = Long.parseLong( mid );
String result = "";
do {
字符串长度0到59long a = int_mid % 62;
result = str62keys.charAt( ( int ) a ) + result;
int_mid = ( int_mid - a ) / 62;
} while ( int_mid > 0 );
return leftPad( result, 4, '0' );
}
// / <summary>
/
/ / Encode62s to int.
// / </summary>
// / <param name="str62">The STR62.</param>
// / <returns>System.Int64.</returns>
private static long encode62ToInt( String str62 ) {
long i10 = 0;
for ( int i = 0; i < str62.length( ); i++ ) {
double n = str62.length( ) - i - 1;
i10 += str62keys.indexOf( str62.charAt( i ) ) * Math.pow( 62, n );
}
String temp = leftPad( String.valueOf( i10 ), 7, '0' );
/
/ Long.TryParse(temp, out i10);
try {
i10 = Long.parseLong( temp );
} catch ( Exception e ) {
// TODO: handle exception
} finally {
return i10;
}
}
// 左边补
public static String leftPad( String s, int size, char padChar ) {
int length = s.length( );
if ( length == 0 ) {
return s;
}
int pads = size - length;
if ( pads <= 0 ) {
return s;
}
return padding( pads, padChar ).concat( s );
}
// 填充
private static String padding( int repeat, char padChar ) {
if ( repeat < 0 ) {
throw new IndexOutOfBoundsException( "Cannot pad a negative amount: " + repeat );        }
char[] buf = new char[ repeat ];
for ( int i = 0; i < buf.length; i++ ) {
buf[ i ] = padChar;
}
return new String( buf );
}
/**
* 左起截取字符串
*
* @param s
* @param len
* @return
*/
public static String left( String s, int begin, int len ) {
int length = length( s );
if ( length <= len ) {
return s;
}
return s.substring( begin, begin > 0 ? begin + len : len );
}
/**
* 长度
* @param s
* @return
*/
public static int length( String s ) {
return s != null ? s.length( ) : 0;    }
}

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