Int to Char...I don't know what the problem is here

Question

Everything compiles fine here, and if I print out the "encryption" variable I get what looks like it would be right, converted into chars, but when I try to convert the int to char(my char variable for that is 'w'), my compiler freaks out, I don't even know what it's doing it doesn't give me an error, but sometimes it prints out nothing but sometimes it prints out "puTTypUTtypuTTYPUtty" ...why is it doing that and what is wrong with what I am doing?.
public class encrypt
public static void main(String[] args)
String plainText = "hello, my name is christy.";
String keyWord = "nice to meet you";
int encryption = 0;
char ch = 'a';
char c = 'a';
int encryptor = 0;
int charCode;
int sum = 0;
char w;
int i = plainText.length();
int j = plainText.length();
int[] plain = new int;
int[] key = new int[j];
for(i=0; i<plainText.length(); i++)
ch = plainText.charAt(i);
charCode = (int)ch;
if(charCode > 97 && charCode < 122)//make lowercase
{charCode = charCode - 97;}
if(charCode > 65 && charCode < 90)
{charCode = charCode - 65;}
plain[i] = charCode;
     for(j=0; j<keyWord.length(); j++)
c = keyWord.charAt(j);
int chCode = (int)c;
if(chCode > 97 && chCode < 122)
{chCode = chCode - 97;}
if(chCode > 65 && chCode < 90)
{chCode = chCode - 65;}
key[j] = chCode;
encryption = (plain[i] + key[j]) % 26;
w = (char)encryption;
System.out.print(w);

Answer 1

And for that matter, use increment/decrement assignment operators (like += and -=) instead of verbosely repeating the variable. And if you're going to use character-by-character case conversion, use the methods in Character don't do it like a C programmer circa 1982. And if this is anything other than a homework assignment, use encryption code provided in the JDK; don't reinvent it.