nrs.util
Class PostfixCalculator

java.lang.Object
  nrs.util.PostfixCalculator

public class PostfixCalculator

extends java.lang.Object

Postfix calculator.

Specify a calculation using postfix notation and then call calculate to get the value. In addition to numbers and operators this calculator also understands functions from the java.lang.Math class which take one or two double arguments. It also understands the random function which takes no arguments.

To see an example of how this class works try the following:

java -cp nrsutils.jar nrs.util.PostfixCalculator "36 2 * toRadians cos"

which in normal terms can be translated as cos(toRadians(36 * 2)) with an answer of 0.30901699437494745.

In programmatic use, you would create a new instance of PostfixCalculator and then use the add* methods to add numbers and operands to the stack. The alternative method is to use the parseCalculation method which will parse a space separated String. The getResult method then returns the answer as a double.

The supported mathematical operators are:

Divide

Operator	Usage	Description
+	op1 op2 +	Add
-	op1 op2 -	Subtract
*	op1 op2 *	Multiply
/	op1 op2 /
%	op1 op2 %	Remainder
&	op1 op2 &	Bitwise AND
|	op1 op2 |	Bitwise OR
^	op1 op2 ^	Bitwise XOR
~	op1 ~	Bitwise complement
<<	op1 op2 <<	Shift bits of op1 left by distance op2; fills with zero bits on the right-hand side
>>	op1 op2 >>	Shift bits of op1 right by distance op2; fills with highest (sign) bit on the left-hand side
>>>	op1 op2 >>>	Shift bits of op1 right by distance op2; fills with zero bits on the left-hand side

Author:

Copyright © 2003-2005 Nick Sydenham <nsydenham@yahoo.co.uk>

Field Summary

static java.lang.String

allowedOperands Allowed operands are + - / * % & | ^ << >> <<<

Constructor Summary

PostfixCalculator()

Method Summary

void	add(double num) Add a double
void	add(long num) Add a long
void	add(java.lang.Object item) Add edither a number or operator to the stack
void	addMathFunction(java.lang.String function) Add a math function to the stack
void	addNumber(java.lang.Number num) Add a number to the stack
void	addOperand(java.lang.String op) Add an operand
void	clear() Remove all previously added values, functions and operands
java.lang.Double	getResult() Returns the top value on the stack.
static boolean	isMathFunction(java.lang.String param) Checks to see if the specified parameter is a java.lang.Math method
static boolean	isOperand(java.lang.String param) Checks to see if the specified parameter is an operand
static void	main(java.lang.String[] args) Main method used for testing
void	parseCalculation(java.lang.String calculation) Instead of passing number and operands one at a time they can be passed in altogether
void	reset() Reset the calculator
java.lang.String	toString() Get a description of the internal Stack

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

allowedOperands

public static final java.lang.String allowedOperands

Allowed operands are + - / * % & | ^ << >> <<<

See Also:

Constant Field Values

Constructor Detail

PostfixCalculator

public PostfixCalculator()

Method Detail

isOperand

public static boolean isOperand(java.lang.String param)

Checks to see if the specified parameter is an operand

Returns:

true if it is an operand, false otherwise

isMathFunction

public static boolean isMathFunction(java.lang.String param)

Checks to see if the specified parameter is a java.lang.Math method

Returns:

true if it is a Math method, false otherwise

add

public void add(java.lang.Object item)
         throws java.lang.IllegalArgumentException

Add edither a number or operator to the stack

Parameters:

item - either Number or String (operand or Math method)

Throws:

java.lang.IllegalArgumentException - item wasn't a Number, operand or Math method

add

public void add(long num)

Add a long

add

public void add(double num)

Add a double

addNumber

public void addNumber(java.lang.Number num)

Add a number to the stack

Parameters:

num - Number to add

addOperand

public void addOperand(java.lang.String op)
                throws java.lang.IllegalArgumentException

Add an operand

Parameters:

op - must be one of the allowed operands

Throws:

java.lang.IllegalArgumentException - either incorrect op or stack doesn't have any numbers on it yet

See Also:

allowedOperands

addMathFunction

public void addMathFunction(java.lang.String function)
                     throws java.lang.IllegalArgumentException

Add a math function to the stack

Parameters:

function - function as defined by java.lang.Math. The methods allowed are random and methods which take one or two double arguments.

Throws:

java.lang.IllegalArgumentException

See Also:

Math

reset

public void reset()

Reset the calculator

getResult

public java.lang.Double getResult()

Returns the top value on the stack. This may be null if the stack is empty or the top of the stack isn't a number.

Returns:

the top of the stack converted to a Double

parseCalculation

public void parseCalculation(java.lang.String calculation)

Instead of passing number and operands one at a time they can be passed in altogether

Parameters:

calculation - space separated string of numbers, operands and functions

clear

public void clear()

Remove all previously added values, functions and operands

toString

public java.lang.String toString()

Get a description of the internal Stack

main

public static void main(java.lang.String[] args)

Main method used for testing