Java programming calculator

I had to make a calculator using stacks. Here is what i have so far. For some reason, the equal sign doesn't work. Can someone help me fix this. The code shows no error,
http://pastebin.com/SjemnE0V

String numbers[]={"0","1","2","3","4","5","6","7","8","9","+","-","*","/",".","CE","C","=","+/-"};

I don't think you belong here.