تتبع برنامج تحويل Infix To Postfix

public class InToPost {
  private Stack stack;

  private String input;

  private String output = "";

  public InToPost(String in) {
	input = in;
	int stackSize = input.length();
	stack = new Stack(stackSize);
  }

  public String doTrans(String input) {
	for (int j = 0; j < input.length(); j++) {
	  char ch = input.charAt(j);
	  switch (ch) {
	  case '+': 
	  case '-':
		gotOper(ch, 1); 
		break; //   (precedence 1)
	  case '*': // it's * or /
	  case '/':
		gotOper(ch, 2); // go pop operators
		break; //   (precedence 2)
	  case '(': // it's a left paren
		stack.push(ch); // push it
		break;
	  case ')': // it's a right paren
		gotParen(ch); // go pop operators
		break;
	  default: // must be an operand
		output = output + ch; // write it to output
		break;
	  }
	}
	while (stack.isEmpty()) {
	  output = output + stack.pop();

	}
	System.out.println(output);
	return output; // return postfix
  }

  public void gotOper(char opThis, int prec1) {
	while (!stack.isEmpty()) {
	  char opTop =stack.pop();
	  if (opTop == '(') {
	 stack.push(opTop);
		break;
	  }// it's an operator
	  else {// precedence of new op
		int prec2;
		if (opTop == '+' || opTop == '-')
		  prec2 = 1;
		else
		  prec2 = 2;
		if (prec2 < prec1) // if prec of new op less
		{ //	than prec of old
		  stack.push(opTop); // save newly-popped op
		  break;
		} else
		  // prec of new not less
		  output = output + opTop; // than prec of old
	  }
	}
	stack.push(opThis);
  }

  public void gotParen(char ch){ 
	while (!stack.isEmpty()) {
	  char chx = stack.pop();
	  if (chx == '(') 
		break; 
	  else
		output = output + chx; 
	}
  }
}

البرنامج بيحول من infix to postfix محتاجة مساعده بتتبعه وكلمة break ايش بتعمل ؟

اتمنى منكم المساعده