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added proj2 .java files

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git-svn-id: svn://anubis/gvsu@75 45c1a28c-8058-47b2-ae61-ca45b979098e
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josh 2008-03-21 20:50:52 +00:00
parent 8818779daf
commit 6856920fa3
4 changed files with 297 additions and 0 deletions
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84
cs621/proj2/Calculator.java Normal file
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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());
}
}
}

37
cs621/proj2/MyApp.java Normal file
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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);
}
}
}

116
cs621/proj2/Rational.java Normal file
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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);
}
}

60
cs621/proj2/RationalStack.java Normal file
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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();
}
}