Hi i need the explanation for the code below.

Question

public class RMIClient_CipherKey
public RMIClient_CipherKey()
public boolean changeKey(String s)
int ai[] = new int[s.length()];
for(int i = 0; i < ai.length; i++)
switch(s.charAt(i))
case 65: // 'A'
ai[i] = 1;
break;
case 66: // 'B'
ai[i] = 2;
break;
case 67: // 'C'
ai[i] = 3;
break;
case 68: // 'D'
ai[i] = 4;
break;
case 69: // 'E'
ai[i] = 5;
break;
case 70: // 'F'
ai[i] = 6;
break;
case 71: // 'G'
ai[i] = 7;
break;
case 72: // 'H'
ai[i] = 8;
break;
case 73: // 'I'
ai[i] = 9;
break;
case 74: // 'J'
ai[i] = 10;
break;
case 75: // 'K'
ai[i] = 11;
break;
case 76: // 'L'
ai[i] = 12;
break;
case 77: // 'M'
ai[i] = 13;
break;
case 78: // 'N'
ai[i] = 14;
break;
case 79: // 'O'
ai[i] = 15;
break;
case 80: // 'P'
ai[i] = 16;
break;
case 81: // 'Q'
ai[i] = 17;
break;
case 82: // 'R'
ai[i] = 18;
break;
case 83: // 'S'
ai[i] = 19;
break;
case 84: // 'T'
ai[i] = 20;
break;
case 85: // 'U'
ai[i] = 21;
break;
case 86: // 'V'
ai[i] = 22;
break;
case 87: // 'W'
ai[i] = 23;
break;
case 88: // 'X'
ai[i] = 24;
break;
case 89: // 'Y'
ai[i] = 25;
break;
case 90: // 'Z'
ai[i] = 26;
break;
case 32: // ' '
ai[i] = 27;
break;
case 33: // '!'
case 34: // '"'
case 35: // '#'
case 36: // '$'
case 37: // '%'
case 38: // '&'
case 39: // '\''
case 40: // '('
case 41: // ')'
case 42: // '*'
case 43: // '+'
case 44: // ','
case 45: // '-'
case 46: // '.'
case 47: // '/'
case 48: // '0'
case 49: // '1'
case 50: // '2'
case 51: // '3'
case 52: // '4'
case 53: // '5'
case 54: // '6'
case 55: // '7'
case 56: // '8'
case 57: // '9'
case 58: // ':'
case 59: // ';'
case 60: // '<'
case 61: // '='
case 62: // '>'
case 63: // '?'
case 64: // '@'
default:
key = defaultKey;
return false;
if(ai.length > 0)
key = ai;
else
return false;
return true;
public String encryptLine(String s)
String s1 = "";
int i = 0;
for(int j = 0; j < s.length(); j++)
int k = s.charAt(j) + key;
if(k > 126)
k -= 95;
s1 = s1 + (char)k;
if(++i >= key.length)
i = 0;
return s1;
public String decryptLine(String s)
String s1 = "";
int i = 0;
for(int j = 0; j < s.length(); j++)
int k = s.charAt(j) - key[i];
if(k < 32)
k += 95;
s1 = s1 + (char)k;
if(++i >= key.length)
i = 0;
return s1;
private final int defaultKey[] = {
9, 27, 12, 15, 22, 5, 27, 10, 1, 22,
1
private int key[] = {
9, 27, 12, 15, 22, 5, 27, 10, 1, 22,
1

Answer 1

Hi.
The first method is confusing as most of it doesn't do anything. You could replace it with a one liner. ;)
It returns true if and only if the string has one or more characters and none of those characters are one of the special characters. The special characters include digits but not letters such as [ ] { } \
The second and third methods implement a simple rotation encryption for up to 11 character strings. (Longer strings result in an ArrayIndexOutOfBoundException)