Hello people,

I am trying to implement a program in Java that simulates a simple calculator.

Here is the thing, I have to start by creating an abstract class that represents any binary which i'm thinking it has to accept only two arguments and then i have to implement various sub classes of this class. I know that my abstract class should at least include two methods but i am not quite sure what objects i should include in it! I also know that my subclasses should include the binary as well as operations of addition subtraction multiplication and division and i should use NO static methods. I have already started and come up with the following:

import java.util.Scanner;

public abstract class (class name)

{

double opt1;

double op2;

public void evaluate(double op1, double op2);

}

public void display();

}

public class Binarycalculator extends ArithmeticExpression {

## 5 Replies - 13238 Views - Last Post: 14 November 2010 - 04:01 PM

### #1

# Simple Binary Calculator in Java (Abstract class)

Posted 14 November 2010 - 12:15 PM

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**Replies To:** Simple Binary Calculator in Java (Abstract class)

### #2

## Re: Simple Binary Calculator in Java (Abstract class)

Posted 14 November 2010 - 12:23 PM

It appears that some of your code wasn't pasted into the message. I'm sure that would help us.

Also...Pleas remember--

Also...Pleas remember--

### #3

## Re: Simple Binary Calculator in Java (Abstract class)

Posted 14 November 2010 - 12:34 PM

import java.util.Scanner; public abstract class (class name) { double opt1; double op2; public void evaluate(double op1, double op2); } public void display(); } public class Binarycalculator extends ArithmeticExpression {

### #4

## Re: Simple Binary Calculator in Java (Abstract class)

Posted 14 November 2010 - 12:59 PM

You have a misplaced "}" in your code after the declaration on the evaluate method.

also, when not implementing a method you must declare it as abstract!

like so:

you will have to implement it in the derived class.

As for the assignment, is it a binary calculator? or decimal calculator? I am not sure what exacly you mean...

I'll guess you want to make a decimal number calculator, and by binary you mean it accepts two decimals.

you can start by declaring an abstract class called ArithmeticOperation. have 2 double variables, pass them to the constructor.

have the evaluate method declared as abstract, and override it in each of the subclasses (multiply, divide, substract add).

something like:

to declare a subclass of ArithmeticOperation, simple declare it as:

also, when not implementing a method you must declare it as abstract!

like so:

public abstract void print();

you will have to implement it in the derived class.

As for the assignment, is it a binary calculator? or decimal calculator? I am not sure what exacly you mean...

I'll guess you want to make a decimal number calculator, and by binary you mean it accepts two decimals.

you can start by declaring an abstract class called ArithmeticOperation. have 2 double variables, pass them to the constructor.

have the evaluate method declared as abstract, and override it in each of the subclasses (multiply, divide, substract add).

something like:

public abstract class ArithmeticOperation { private double var1; private double var2; public ArithmeticOperation(double var1, double var2){ this.var1 = var1; this.var2 = var2; } public abstract double evaluate(); //perform calculations here //any other methods? }

to declare a subclass of ArithmeticOperation, simple declare it as:

public SubClass extends ArithmeticOperation { //don't forget to override evaluate!!! }

### #5

## Re: Simple Binary Calculator in Java (Abstract class)

Posted 14 November 2010 - 03:02 PM

Thank you so much for your reply,

it is actually a binary calculator, each sub class should include the binary and the operations (Addition, subtraction, multiplication and division). Method evaluate should evaluate the arithmetic operation/expression and return it as a double. For example, calling it in an object representing expression "(5.0+8.1)*(2.0)" should return 26.2.

Whereas method display should print the raw unevaluated on the screen. For example,

calling it in an object representing expression "(5.0+8.1)*(2.0)" should display the string

"(5.0+8.1)*(2.0)" without the quotes. I have no idea how i should be doing that any clues?

it is actually a binary calculator, each sub class should include the binary and the operations (Addition, subtraction, multiplication and division). Method evaluate should evaluate the arithmetic operation/expression and return it as a double. For example, calling it in an object representing expression "(5.0+8.1)*(2.0)" should return 26.2.

Whereas method display should print the raw unevaluated on the screen. For example,

calling it in an object representing expression "(5.0+8.1)*(2.0)" should display the string

"(5.0+8.1)*(2.0)" without the quotes. I have no idea how i should be doing that any clues?

### #6

## Re: Simple Binary Calculator in Java (Abstract class)

Posted 14 November 2010 - 04:01 PM

Do you have to get the arithmetic expression as a String?

In that case the class and logic should be different.

First check if the input is valid. (a valid arithmetic expression).

then look for the operations char ('(' ,')', '+', '-', '*', '\')

just calculate it in the correct order (first braces, then mult\div, and then plus,minus)

There are some code snippets similar to what you need.

check this one for example:

This will help you design your code:

http://www.dreaminco...snippet5781.htm

In that case the class and logic should be different.

First check if the input is valid. (a valid arithmetic expression).

then look for the operations char ('(' ,')', '+', '-', '*', '\')

just calculate it in the correct order (first braces, then mult\div, and then plus,minus)

There are some code snippets similar to what you need.

check this one for example:

This will help you design your code:

http://www.dreaminco...snippet5781.htm

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