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POSimple Calculator program java
 

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    <p>I'm supposed to create a program which simulates a very simple calculator</p> <p>So I have been asked to implement an abstract class that represents binary (having 2 arguments) arithmetic expression. I've also made 4 subclasses - division, addition, etc. </p> <p>However, i need to use these classes to be "able to represent any arbitrary expression (i.e. an expression with an arbitrary number of terms), for example an expression like <code>(5.0+8.1)*(2.0)</code> or <code>((5.0+8.1)*(2.0))/12.5</code> as quoted by my crswork spec. </p> <p>In other words, my calculator must be able to use any arithmetic expression. </p> <p>Pls help. </p> <pre><code>public abstract class ArithmeticExpression { // base abstract superclass double left; double right; double result; public abstract void evaluate(); public abstract void display(); } // ------------------------------------ Addition subclassed from base class public class Addition extends ArithmeticExpression { public Addition(double x, double y) { this.left = x; this.right = y; } @Override public void evaluate() { result = left + right; } @Override public void display() { System.out.println ("The expression and result is: " + left + " + " + right + " = " + result); } } // ------------------------------------ Subtract subclassed from base class public class Subtract extends ArithmeticExpression { public Subtract(double x, double y) { this.left = x; this.right = y; } @Override public void evaluate() { result = left - right; } @Override public void display() { System.out.println ("The expression and result is: " + left + " - " + right + " = " + result); } } // ------------------------------------ Mulitplication subclassed from base // class public class Multiplication extends ArithmeticExpression { public Multiplication(double x, double y) { this.left = x; this.right = y; } @Override public void evaluate() { result = left * right; } @Override public void display() { System.out.println ("The expression and result is: " + left + " * " + right + " = " + result); } } // ------------------------------------ Division subclassed from base class public class Division extends ArithmeticExpression { public Division(double x, double y) { this.left = x; this.right = y; } @Override public void evaluate() { result = left / right; } @Override public void display() { System.out.println("The expression and result is: " + left + " / " + right + " = " + result); } } </code></pre> <p>this is my attampt at making evaluate method return value. Does it work?</p> <pre><code>public abstract ArithmeticExpression evaluate(); //------------------------------------ Addition subclassed from base class public class Addition extends ArithmeticExpression { public Addition(double x, double y) { this.left = x; this.right = y; } @Override public ArithmeticExpression evaluate() { result = left + right; return this; } </code></pre>
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    1. COSome hints: parse from right to left; find the inner most operation based on parenteses and start there; define your parsing code recursively.
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    2. COWhat course are you taking? This almost certainly asks for a syntax tree parser. The expression string gets parsed before calling the 4 basic computations you implemented.
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    3. COTaking computer science. is that what i should do? parse the expression string? And how?
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