Package com.project.calculator

Class PostfixEvaluation

java.lang.Object

com.project.calculator.PostfixEvaluation

public class PostfixEvaluation
extends Object

The PostfixEvaluation class evaluates a mathematical expression in postfix notation using a stack-based approach.

This class performs the following tasks:

• Processes postfix expressions containing operands and operators.
• Evaluates the expression using a stack.
• Updates the result in the MainUI instance.

Constructor Summary

Constructors

Constructor	Description
PostfixEvaluation(List<String> expression, MainUI mainUiInstance)	Constructs a PostfixEvaluation object and evaluates the given postfix expression.

Method Summary

Modifier and Type	Method	Description
private double	evaluatePostfix(List<String> expression)	Evaluates the given postfix expression.
static boolean	isOperator(String token)	Checks if the given token is a mathematical operator.
static double	performOperation(double num1, double num2, String operator)	Performs a mathematical operation on two operands based on the given operator.

Methods inherited from class java.lang.Object

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

Constructor Details

PostfixEvaluation

PostfixEvaluation(List<String> expression,
 MainUI mainUiInstance)

Constructs a PostfixEvaluation object and evaluates the given postfix expression.

The result is stored in the MainUI instance for display.

Parameters:

expression - The postfix expression to evaluate (as a List<String>).

mainUiInstance - The MainUI instance to store the result.

Method Details

evaluatePostfix

private double evaluatePostfix(List<String> expression)

Evaluates the given postfix expression.

The method uses a stack to:

• Push operands onto the stack.
• Pop two operands when an operator is encountered.
• Perform the operation and push the result back onto the stack.

Parameters:

expression - The postfix expression as a List<String>.

Returns:

The result of the evaluated expression as a double.

isOperator

public static boolean isOperator(String token)

Checks if the given token is a mathematical operator.

Supported operators: +, -, *, /, %.

Parameters:

token - The token to check.

Returns:

true if the token is an operator, false otherwise.

performOperation

public static double performOperation(double num1,
 double num2,
 String operator)

Performs a mathematical operation on two operands based on the given operator.

The supported operations include:

• + → Addition
• - → Subtraction
• * → Multiplication
• / → Division
• % → Modulus

Parameters:

num1 - The first operand.

num2 - The second operand.

operator - The mathematical operator as a String.

Returns:

The result of the operation as a double.