Description
The first programming project involves writing a program that converts prefix expressions to postfix and postfix expressions to prefix. Customary infix expression place the operator between the two operands. In a prefix expression, the operator comes before the two operands. In a postfix expression it comes after them. One benefit of prefix and postfix expressions is that they never require parentheses nor rules regarding precedence or associativity.
The program for this project should consist of three classes. The main class should create a GUI that allows the user to input an expression in either prefix or postfix and convert it to postfix or prefix, respectively. The GUI should look as follows:
The GUI must be generated by code that you write. You may not use a drag-and-drop GUI generator.
The second class should contain the code to perform the conversions. The pseudocode for prefix to postfix, which requires two stacks, is shown below:
tokenize the string containing the prefix expression while there are more tokens
push the token onto a reversal stack if it is not a space while the reversal stack is not empty    pop the next token from the reversal stack
if it is an operand
push it onto the operand stack
else it is an operator
pop two operands off of the operand stack
create a string with the two operands followed         the operator
push that string onto the operand stack pop the postfix expression off the stack
The pseudocode for the postfix to prefix conversion, which requires only one stack, is shown below:
tokenize the string containing the postfix expression while there are more tokens    get the next token
if it is a space        skip it
else if it is an operand  push it onto the operand stack
else it is an operator
pop two operands off of the operand stack
create a string with the operator followed by
two operands
push that string onto the operand stack pop the prefix expression off the stack
Be sure to add any additional methods needed to eliminate any duplication of code.
The input expressions should not be required to contain spaces between tokens unless they are consecutive operands.
The output expressions should always have a space between all symbols. A checked exception SyntaxError should be thrown by the methods that perform the conversions if an empty stack is ever popped or the stack is not empty once the conversion is complete. That exception should be caught in the main class, where a JOptionPane window should be displayed containing an error message.
