I have been referencing this website below to help me write this program in Java

Question

I have been referencing this website below to help me write this program in Java, it contains good information to approach this problem even if you dont know pre and post fix notation as it will explain them both!

http://interactivepython.org/runestone/static/pythonds/BasicDS/InfixPrefixandPostfixExpressions.html

3. (Bonus) Write a Java GUI program that converts a fully parenthesized expression from the infix form to the postfix form by using a stack for storing operators. Three text fields display the contents of the three tapes: input, stack and output. The first ten buttons are used to enter the expression. The "Clear" button clears all tapes and the "Exit" button terminates the program. Input: (a-b) (d+ (c/a) Stack: output: ab-dea Clear Exit

Explanation / Answer

Hi,

The algorithm for converting from infix to postfix is as follows:

import java.io.IOException;

public class InToPost {
private Stack theStack;
private String input;
private String output = "";
public InToPost(String in) {
input = in;
int stackSize = input.length();
theStack = new Stack(stackSize);
}
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 '(':
theStack.push(ch);
break;
case ')':
gotParen(ch);
break;
default:
output = output + ch;
break;
}
}
while (!theStack.isEmpty()) {
output = output + theStack.pop();
}
System.out.println(output);
return output;
}
public void gotOper(char opThis, int prec1) {
while (!theStack.isEmpty()) {
char opTop = theStack.pop();
if (opTop == '(') {
theStack.push(opTop);
break;
} else {
int prec2;
if (opTop == '+' || opTop == '-')
prec2 = 1;
else
prec2 = 2;
if (prec2 < prec1) {
theStack.push(opTop);
break;
}
else output = output + opTop;
}
}
theStack.push(opThis);
}
public void gotParen(char ch) {
while (!theStack.isEmpty()) {
char chx = theStack.pop();
if (chx == '(')
break;
else output = output + chx;
}
}
public static void main(String[] args) throws IOException {
String input = "1+2*4/5-7+3/6";
String output;
InToPost theTrans = new InToPost(input);
output = theTrans.doTrans();
System.out.println("Postfix is " + output + ' ');
}
class Stack {
private int maxSize;
private char[] stackArray;
private int top;
  
public Stack(int max) {
maxSize = max;
stackArray = new char[maxSize];
top = -1;
}
public void push(char j) {
stackArray[++top] = j;
}
public char pop() {
return stackArray[top--];
}
public char peek() {
return stackArray[top];
}
public boolean isEmpty() {
return (top == -1);
}
}
}
Result
The above code sample will produce the following result.

124*5/+7-36/+
Postfix is 124*5/+7-36/+

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