com.drew.lang

Class Rational

Implemented Interfaces:
Serializable

public class Rational
extends java.lang.Number
implements Serializable

Immutable class for holding a rational number without loss of precision. Provides a familiar representation via toString() in form numerator/denominator.

Author:
Drew Noakes http://drewnoakes.com

Constructor Summary

Rational(int numerator, int denominator)
Creates a new instance of Rational.

Method Summary

byte
byteValue()
Returns the value of the specified number as a byte.
double
doubleValue()
Returns the value of the specified number as a double.
boolean
equals(Object obj)
Compares two Rational instances, returning true if they are mathematically equivalent.
float
floatValue()
Returns the value of the specified number as a float.
int
getDenominator()
Returns the denominator.
int
getNumerator()
Returns the numerator.
Rational
getReciprocal()
Returns the reciprocal value of this obejct as a new Rational.
Rational
getSimplifiedInstance()
Simplifies the Rational number.
int
intValue()
Returns the value of the specified number as an int.
boolean
isInteger()
Checks if this rational number is an Integer, either positive or negative.
long
longValue()
Returns the value of the specified number as a long.
short
shortValue()
Returns the value of the specified number as a short.
String
toSimpleString(boolean allowDecimal)
Returns the simplest represenation of this Rational's value possible.
String
toString()
Returns a string representation of the object of form numerator/denominator.

Constructor Details

Rational

public Rational(int numerator,
                int denominator)
Creates a new instance of Rational. Rational objects are immutable, so once you've set your numerator and denominator values here, you're stuck with them!

Method Details

byteValue

public final byte byteValue()
Returns the value of the specified number as a byte. This may involve rounding or truncation. This implementation simply casts the result of doubleValue() to byte.
Returns:
the numeric value represented by this object after conversion to type byte.

doubleValue

public double doubleValue()
Returns the value of the specified number as a double. This may involve rounding.
Returns:
the numeric value represented by this object after conversion to type double.

equals

public boolean equals(Object obj)
Compares two Rational instances, returning true if they are mathematically equivalent.
Parameters:
obj - the Rational to compare this instance to.
Returns:
true if instances are mathematically equivalent, otherwise false. Will also return false if obj is not an instance of Rational.

floatValue

public float floatValue()
Returns the value of the specified number as a float. This may involve rounding.
Returns:
the numeric value represented by this object after conversion to type float.

getDenominator

public final int getDenominator()
Returns the denominator.

getNumerator

public final int getNumerator()
Returns the numerator.

getReciprocal

public Rational getReciprocal()
Returns the reciprocal value of this obejct as a new Rational.
Returns:
the reciprocal in a new object

getSimplifiedInstance

public Rational getSimplifiedInstance()
Simplifies the Rational number.

Prime number series: 1, 2, 3, 5, 7, 9, 11, 13, 17

To reduce a rational, need to see if both numerator and denominator are divisible by a common factor. Using the prime number series in ascending order guarantees the minimun number of checks required.

However, generating the prime number series seems to be a hefty task. Perhaps it's simpler to check if both d & n are divisible by all numbers from 2 -> (Math.min(denominator, numerator) / 2). In doing this, one can check for 2 and 5 once, then ignore all even numbers, and all numbers ending in 0 or 5. This leaves four numbers from every ten to check.

Therefore, the max number of pairs of modulus divisions required will be:

    4   Math.min(denominator, numerator) - 1
   -- * ------------------------------------ + 2
   10                    2

   Math.min(denominator, numerator) - 1
 = ------------------------------------ + 2
                  5
 
Returns:
a simplified instance, or if the Rational could not be simpliffied, returns itself (unchanged)

intValue

public final int intValue()
Returns the value of the specified number as an int. This may involve rounding or truncation. This implementation simply casts the result of doubleValue() to int.
Returns:
the numeric value represented by this object after conversion to type int.

isInteger

public boolean isInteger()
Checks if this rational number is an Integer, either positive or negative.

longValue

public final long longValue()
Returns the value of the specified number as a long. This may involve rounding or truncation. This implementation simply casts the result of doubleValue() to long.
Returns:
the numeric value represented by this object after conversion to type long.

shortValue

public final short shortValue()
Returns the value of the specified number as a short. This may involve rounding or truncation. This implementation simply casts the result of doubleValue() to short.
Returns:
the numeric value represented by this object after conversion to type short.

toSimpleString

public String toSimpleString(boolean allowDecimal)
Returns the simplest represenation of this Rational's value possible.

toString

public String toString()
Returns a string representation of the object of form numerator/denominator.
Returns:
a string representation of the object.

Copyright © 2006 Drew Noakes. All Rights Reserved.