In Java, you will write a postfix calculator program. A postfix calculator uses postfix notation, in which the operator follows the operands.

For example:

3 4 * 4 5 + *

is the posfix notation for (3 * 4) * (4 + 5).

This is a program, not an ADT. If you want, all the code can be in the main() function.

Your program needs to store operands (which are just floating point numbers for this lab) in some appropriate collection type (a stack, queue, or bag). When it reads an operator (like '+' or '\') it must take the two most recent operands, perform the operation, and keep the result as the most recent operand.

(So as not to give it away, I will refer here to the stack, queue, or bag that you use as "the collection".)

Besides the usual arithmetic operators (+, -, *, /), your program needs to recognize two special operators: "sqrt" should take the most recent operand, compute its square root (using Math.sqrt() from the Java library), and add the result back to the collection. "print" should take the most recent operand from the collection, and print it using StdOut.println().

For the print function, just use StdOut.println(). That way, your output will be consistent with mine.

Your program should read strings from standard input and take the appropriate action until the input is exhausted.

So, for example, if the input is:

3 4 * 2 * 1 + sqrt print

your program should print:

5

Let's follow that in detail. Here is what your program should do with each string it reads in the above example:

string	action
3	add to the collection
4	add to the collection
*	remove the 3 and 4, multiply them, and add the result (12) to the collection
2	add to the collection
*	remove the 2 and 12, multiple them, add the result (24) to the collection
1	add to the collection
+	remove the 1 and 24, add them, add the result (25) to the collection
sqrt	remove the 25, compute the square root, and add the result (5) to the collection
print	remove the 5, and print it

HERE is the program I have done so far :

public class PostfixCalc {

public static boolean isNumber(String s) {

try {

Double.parseDouble(s);

return true;

} catch (NumberFormatException e) {

return false;

}

}

public static void main(String[] args) {

// Your code goes here

// Create an appropriate collection to hold operands

// Loop while there is input // read a string // if it is a number (see isNumber() above) // convert to a number (use Double.parseDouble()) // add it to the collection // else // take action appropriate for this operator // operators can be +, -, *, /, sqrt, print

}