added proj2 .java files

git-svn-id: svn://anubis/gvsu@75 45c1a28c-8058-47b2-ae61-ca45b979098e

cs621/proj2/Calculator.java

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+
+import java.util.StringTokenizer;
+
+/**
+ * Calculator implements a RPN calculator that can act on rational values
+ */
+public class Calculator
+{
+    private RationalStack stack = new RationalStack();
+
+    /**
+     * pushOperand adds the given token to the top of the RationalStack object
+     * @param val the token to add
+     */
+    private void pushOperand(String val)
+    {
+        StringTokenizer tokens = new StringTokenizer(val, "/");
+        if (tokens.hasMoreElements())
+        {
+            int num = Integer.parseInt(tokens.nextToken());
+            int denom = 1;
+            if (tokens.hasMoreElements())
+            {
+                denom = Integer.parseInt(tokens.nextToken());
+            }
+            stack.push(new Rational(num, denom));
+        }
+    }
+
+    /**
+     * doOperator performs the action specified by op on the top two elements
+     * of the RationalStack object
+     * @param op the operator to perform
+     */
+    private void doOperator(String op)
+    {
+        if (stack.size() < 2)
+            return;
+
+        Rational two = stack.pop();
+        Rational one = stack.pop();
+        Rational result = new Rational();
+        if (op.equals("+"))
+            result = one.add(two);
+        else if (op.equals("-"))
+            result = one.subtract(two);
+        else if (op.equals("*"))
+            result = one.multiply(two);
+        else if (op.equals("\\"))
+            result = one.divide(two);
+        stack.push(result);
+    }
+
+    /**
+     * run will evaluate the RPN expression and print its result
+     * @param expression the expression to evaluate
+     */
+    public void run(String expression)
+    {
+        StringTokenizer tokens = new StringTokenizer(expression, " ");
+        while (tokens.hasMoreTokens())
+        {
+            String item = tokens.nextToken();
+            if (item.equals("+") || item.equals("-") ||
+                item.equals("*") || item.equals("\\"))
+            {
+                doOperator(item);
+            }
+            else
+            {
+                pushOperand(item);
+            }
+        }
+        
+        if (stack.size() != 1)
+        {
+            System.out.println("Warning: malformed expression");
+        }
+        if (!stack.isEmpty())
+        {
+            System.out.println("Result is: " + stack.pop());
+        }
+    }
+}

cs621/proj2/MyApp.java

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+
+import java.io.BufferedReader;
+import java.io.InputStreamReader;
+
+/**
+ * MyApp is the driver class for Calculator
+ */
+public class MyApp
+{
+    /**
+     * main is the entry point of the program
+     */
+    public static void main (String args[])
+    {
+        BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
+        Calculator myCalc = new Calculator();
+
+        /* loop reading input lines until the user is finished */
+        for (;;)
+        {
+            System.out.println("Enter rational RPN expression (enter empty line to quit):");
+            String line;
+            try
+            {
+                line = in.readLine();
+            }
+            catch (Exception e)
+            {
+                System.out.println("Problem reading a line!");
+                return;
+            }
+            if (line.equals(""))
+                break;
+            myCalc.run(line);
+        }
+    }
+}

cs621/proj2/Rational.java

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+
+/**
+ * Rational is a class which can store a rational number of the form n/d
+ * where n and d are integers, n is the numerator, and d is the denominator
+ */
+public class Rational
+{
+    private int _numerator;
+    private int _denominator;
+
+    /**
+     * This default constructor creates a Rational with value 0
+     */
+    public Rational()
+    {
+        this(0, 1);
+    }
+
+    /**
+     * This constructor creates a Rational with value numerator/denominator
+     * @param numerator the numerator of the Rational
+     * @param denominator the denominator of the Rational
+     */
+    public Rational(int numerator, int denominator)
+    {
+        _numerator = numerator;
+        _denominator = denominator;
+        reduce();
+    }
+
+    /**
+     * add adds this Rational to another
+     * @param other the Rational to add to this one
+     * @return the result of the addition
+     */
+    public Rational add(Rational other)
+    {
+        return new Rational(_numerator * other._denominator +
+                                other._numerator * _denominator,
+                            _denominator * other._denominator);
+    }
+
+    /**
+     * subtract subtracts another Rational from this one
+     * @param other the other Rational to subtract from this one
+     * @return the result of the subtraction
+     */
+    public Rational subtract(Rational other)
+    {
+        return new Rational(_numerator * other._denominator -
+                                other._numerator * _denominator,
+                            _denominator * other._denominator);
+    }
+
+    /**
+     * multiply multiplies this Rational with another
+     * @param other the other Rational to multiply with this one
+     * @return the result of the multiplication
+     */
+    public Rational multiply(Rational other)
+    {
+        return new Rational(_numerator * other._numerator,
+                            _denominator * other._denominator);
+    }
+
+    /**
+     * divide divides another Rational into this one
+     * @param other the other Rational to divide into this one
+     * @return the result of the division
+     */
+    public Rational divide(Rational other)
+    {
+        return new Rational(_numerator * other._denominator,
+                            _denominator * other._numerator);
+    }
+
+    /**
+     * gcd calculates the greatest common divisor between the
+     * numerator and the denominator
+     * @return the greatest common divisor
+     */
+    private int gcd()
+    {
+        int m = _numerator;
+        int n = _denominator;
+        int r;
+        while (n != 0)
+        {
+            r = m % n;
+            m = n;
+            n = r;
+        }
+        return m;
+    }
+
+    /**
+     * reduce reduces the Rational to simplest terms using the gcd
+     * @return itself
+     */
+    public Rational reduce()
+    {
+        int thegcd = gcd();
+        _numerator = _numerator / thegcd;
+        _denominator = _denominator / thegcd;
+        return this;
+    }
+    
+    /**
+     * toString returns a string representation of the Rational in n/m form
+     * @return a string representation of the Rational in n/m form
+     */
+    public String toString()
+    {
+        return _numerator + (_denominator == 1 ? "" : "/" + _denominator);
+    }
+}

cs621/proj2/RationalStack.java

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+
+import java.util.Vector;
+
+/**
+ * RationalStack provides a stack collection of Rational objects
+ */
+public class RationalStack
+{
+    private Vector<Rational> _data = new Vector<Rational>();
+
+    /**
+     * pop will remove and return the Rational object from the top of the stack
+     * @return the Rational at the top of the stack
+     */
+    public Rational pop()
+    {
+        int sz = _data.size();
+        if (sz > 0)
+        {
+            Rational r = _data.remove(sz-1);
+            return r;
+        }
+        return null;
+    }
+
+    /**
+     * push will add a new Rational object to the top of the stack
+     * @param value the Rational object to add to the stack
+     */
+    public void push(Rational value)
+    {
+        _data.add(value);
+    }
+
+    /**
+     * isEmpty will return true if there are no Rational elements on the stack
+     * @return true if there are no Rational elements on the stack
+     */
+    public boolean isEmpty()
+    {
+        return _data.isEmpty();
+    }
+
+    /**
+     * clear will remove all Rational objects from the stack
+     */
+    public void clear()
+    {
+        _data.clear();
+    }
+
+    /**
+     * size returns the number of Rational objects in the stack
+     * @return the number of Rational objects in the stack
+     */
+    public int size()
+    {
+        return _data.size();
+    }
+}