CMIS 241

Week 8 Homework
Due: 10 April

Using the Postfix.java as a base, make a postfix boolean expression
evaluator program.  This is very similar to the postfix integer
expression evaluator except the operands can only be true and false
and the operators are !, && and ||, the three logical operators.

Example expressions:

true false &&
  postfix for: true && false  = false
  
true false ! &&
  postfix for: true && !false  = true

true true ! false || ! && true false && ||
  postfix for: true && !(!true || false) || (true && false)  = true


The program is analogous to the Postfix.java.  The stack contains
Boolean objects.

Note: a Boolean object can be created from a String directly without
having to do a parseBoolean (Note note: parseBoolean is brand new in
recent updates of JDK 1.5 so you might not even have it; don't worry,
don't use it anyway, use:
new Boolean(myString) 
which will create a true object if myString is any case of "true"

! is a unary operator, so only the most recently pushed operand is
popped off the stack and has the ! operator applied to it.


Submit the .java file to Tycho.  Do not zip a single file!