我现在要一端加密程序，实现对一串字符串的加密，想利用ASCII值进行换算加密。
该怎么做？或有没有其他好的建议？

以下为一段加密程序，供参考。
其中Decrype为解密，Encrypt为加密。
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package com.utility;

public class Decode
{
public static String Decrypt(String str)
{
String encoderText="lsdfoglkwjemc-091324jlkmsda-0sd=1234;l;lsdkOPIER203-4LKJSLDJAS0D925JKNNC,MANSLDJQ32ELK1N4SAIp089er0234lkjo9df82l3kjlknf,nzxc,mn;lasdj9wquelq;d]qowe[;wq;qkwellsdkfj0-0POPOAR0W8RPOp-02@#$sdklj$#)0asdlksadLKJFA9820934)(&$3ij09sdj34-sdfj2po345-09dlkfjlkv,mxncv;laskdkl/a;au093hakjh2389~!@%&*%#&^539478(*&)^(&^_*8-*_+++|78w3ihsdnmnclksdj)(*#%*_@$(+#@$)&@#^*&^#@$()(*#@$HDFIkdhfgkjh098k;ldsk.sdv.c,msd;flkp0w34;2lk-=sd0p121o39-werl2k3;4lj09sdflskjlekfj,mv,mcxvjlksjdflksjdl*(#@!&akhduyqweperilmmdxcasnd*(#@9879327kjhasudfewr kwehriwueyrhc ausdgiq7w8e71 cdsh93ol2q32879y8932qwhdkjanhdskjaoe*&w#jh$)(*dsFshc na89wue32e981yewher12(*&#quds)(*i3o1928osaihdaklsdkalkduqowe3290874kljhklasdhlijhqweio4hwe89(*$#$eriho349oij(#*q$OIJHO)(&*#$_)(IUDSOIUoiOIUSAODFU034liusdrogiuet0lsdmc,.mg;lq-091lk3l;kjsdf--123098fe*(JOKJSFD983345oihjdp0(#*$&#@!HKJH!(@#*&ioysdk@#)uhOA7E98R7239845K(*&(#@*$&HKFDJHWERYIWoi)(*&#@&^%@!dsfoi;.;,p[osklejr230897*(&we2&^%@78*(&#@!(7~&*~^@*&^#(*&auroiqkjwrhoasdf89qlrlkjpour09werk23jh";
int seed, pre;
try{
seed = DecodeChar(str,0);
} catch (NumberFormatException e)
{
return "";
}
try{
    pre = DecodeChar(str,2);
}catch (NumberFormatException e)
{
return "";
}

    pre = pre&3;

    String ret = "";
    int x;
    int i,j;
    int len = str.length();
    int elen = encoderText.length();


for (i=pre+pre+4,j=seed;i=elen)
j=0;
    }

    return ret;
}

public static String Encrypt(String str)
{
String encoderText="lsdfoglkwjemc-091324jlkmsda-0sd=1234;l;lsdkOPIER203-4LKJSLDJAS0D925JKNNC,MANSLDJQ32ELK1N4SAIp089er0234lkjo9df82l3kjlknf,nzxc,mn;lasdj9wquelq;d]qowe[;wq;qkwellsdkfj0-0POPOAR0W8RPOp-02@#$sdklj$#)0asdlksadLKJFA9820934)(&$3ij09sdj34-sdfj2po345-09dlkfjlkv,mxncv;laskdkl/a;au093hakjh2389~!@%&*%#&^539478(*&)^(&^_*8-*_+++|78w3ihsdnmnclksdj)(*#%*_@$(+#@$)&@#^*&^#@$()(*#@$HDFIkdhfgkjh098k;ldsk.sdv.c,msd;flkp0w34;2lk-=sd0p121o39-werl2k3;4lj09sdflskjlekfj,mv,mcxvjlksjdflksjdl*(#@!&akhduyqweperilmmdxcasnd*(#@9879327kjhasudfewr kwehriwueyrhc ausdgiq7w8e71 cdsh93ol2q32879y8932qwhdkjanhdskjaoe*&w#jh$)(*dsFshc na89wue32e981yewher12(*&#quds)(*i3o1928osaihdaklsdkalkduqowe3290874kljhklasdhlijhqweio4hwe89(*$#$eriho349oij(#*q$OIJHO)(&*#$_)(IUDSOIUoiOIUSAODFU034liusdrogiuet0lsdmc,.mg;lq-091lk3l;kjsdf--123098fe*(JOKJSFD983345oihjdp0(#*$&#@!HKJH!(@#*&ioysdk@#)uhOA7E98R7239845K(*&(#@*$&HKFDJHWERYIWoi)(*&#@&^%@!dsfoi;.;,p[osklejr230897*(&we2&^%@78*(&#@!(7~&*~^@*&^#(*&auroiqkjwrhoasdf89qlrlkjpour09werk23jh";

int seed = (int)Random(255);
int pre = seed & 3;
int len = str.length();
int elen = encoderText.length();
int i,j;

String ret = "";
ret += EncodeChar(seed);
ret += EncodeChar((((int)Random(255))&0xfc)+pre);
for (i=0;i9){
        s += (char)(((int)x)-10+0x61);
    }
    else{
        s += (int)x;
    }
    x = c%16;
    if (x>9){
        s += (char)( ((int)x) -10+0x61);
    }
    else{
        s += (int)x;
    }
    return s;
}

public static int DecodeChar(String str,int i) throws NumberFormatException
{
return Integer.parseInt(str.substring(i,i+2),16);
}
}
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