public String doTrans(){
		for(int j=0; j<input.length(); j++){
			char ch = input.charAt(j);
			switch (ch) {
			case '+':
				
			case '-':
				gotOper(ch, 1);
				break;
			case '*':
			case '/':
				gotOper(ch, 2);
				break;
			case '(':
				stack.push(ch);
				break;
			case ')':
				gotParen(ch);
				break;

			default:
				output = output + ch;
				break;
			}
		}
		
		while(!stack.isEmpty()){
			output = output + stack.pop();
		}
		return output;
	}