Writing a command-line Java program that evaluates NORMAL Polish notation (NPN) formulas. Here are the details:

• When run from the command line your program must read from standard input an NPN

  formula.

• You can assume there is a space between every operator and number. Every number will be

  a 32-bit integer.

• Your program should be able to correctly handle the operations: +, -, x.

  IMPORTANT: be careful that your program recognises precisely the three characters above (plus sign, minus sign, and the lowercase letter x, respectively).

• Your program then should write to standard out a single line with the correct output in a standard integer format. The following example shows the correct behaviour for your program:

echo + 75 125 | java test 200

Other examples of NPN formulas are:

• 3( result is 3)

• x 2 0 (result is 0)

• x + 2 3 + 2 2 (result is 20)

• + x 2 3 4 (result is 10)

IMPORTANT

• As with all other assignments you may NOT use any Java standard library class or method other than for input/output.