org.apache.commons.lang.math
Class Fraction

java.lang.Object
  java.lang.Number
      org.apache.commons.lang.math.Fraction

All Implemented Interfaces:

Serializable, Comparable

public final class Fraction
extends Number
implements Comparable

Fraction is a Number implementation that stores fractions accurately.

This class is immutable, and interoperable with most methods that accept a Number.

Since:

2.0

Version:

$Id: Fraction.java 905636 2010-02-02 14:03:32Z niallp $

Author:

Apache Software Foundation, Travis Reeder, Tim O'Brien, Pete Gieser, C. Scott Ananian

See Also:

Serialized Form

Field Summary

static Fraction	FOUR_FIFTHS Fraction representation of 4/5.
static Fraction	ONE Fraction representation of 1.
static Fraction	ONE_FIFTH Fraction representation of 1/5.
static Fraction	ONE_HALF Fraction representation of 1/2.
static Fraction	ONE_QUARTER Fraction representation of 1/4.
static Fraction	ONE_THIRD Fraction representation of 1/3.
static Fraction	THREE_FIFTHS Fraction representation of 3/5.
static Fraction	THREE_QUARTERS Fraction representation of 3/4.
static Fraction	TWO_FIFTHS Fraction representation of 2/5.
static Fraction	TWO_QUARTERS Fraction representation of 2/4.
static Fraction	TWO_THIRDS Fraction representation of 2/3.
static Fraction	ZERO Fraction representation of 0.

Method Summary

Fraction	abs() Gets a fraction that is the positive equivalent of this one.
Fraction	add(Fraction fraction) Adds the value of this fraction to another, returning the result in reduced form.
int	compareTo(Object object) Compares this object to another based on size.
Fraction	divideBy(Fraction fraction) Divide the value of this fraction by another.
double	doubleValue() Gets the fraction as a double.
boolean	equals(Object obj) Compares this fraction to another object to test if they are equal.
float	floatValue() Gets the fraction as a float.
int	getDenominator() Gets the denominator part of the fraction.
static Fraction	getFraction(double value) Creates a Fraction instance from a double value.
static Fraction	getFraction(int numerator, int denominator) Creates a Fraction instance with the 2 parts of a fraction Y/Z.
static Fraction	getFraction(int whole, int numerator, int denominator) Creates a Fraction instance with the 3 parts of a fraction X Y/Z.
static Fraction	getFraction(String str) Creates a Fraction from a String.
int	getNumerator() Gets the numerator part of the fraction.
int	getProperNumerator() Gets the proper numerator, always positive.
int	getProperWhole() Gets the proper whole part of the fraction.
static Fraction	getReducedFraction(int numerator, int denominator) Creates a reduced Fraction instance with the 2 parts of a fraction Y/Z.
int	hashCode() Gets a hashCode for the fraction.
int	intValue() Gets the fraction as an int.
Fraction	invert() Gets a fraction that is the inverse (1/fraction) of this one.
long	longValue() Gets the fraction as a long.
Fraction	multiplyBy(Fraction fraction) Multiplies the value of this fraction by another, returning the result in reduced form.
Fraction	negate() Gets a fraction that is the negative (-fraction) of this one.
Fraction	pow(int power) Gets a fraction that is raised to the passed in power.
Fraction	reduce() Reduce the fraction to the smallest values for the numerator and denominator, returning the result.
Fraction	subtract(Fraction fraction) Subtracts the value of another fraction from the value of this one, returning the result in reduced form.
String	toProperString() Gets the fraction as a proper String in the format X Y/Z.
String	toString() Gets the fraction as a String.

Methods inherited from class java.lang.Number

byteValue, shortValue

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Field Detail

ZERO

public static final Fraction ZERO

Fraction representation of 0.

ONE

public static final Fraction ONE

Fraction representation of 1.

ONE_HALF

public static final Fraction ONE_HALF

Fraction representation of 1/2.

ONE_THIRD

public static final Fraction ONE_THIRD

Fraction representation of 1/3.

TWO_THIRDS

public static final Fraction TWO_THIRDS

Fraction representation of 2/3.

ONE_QUARTER

public static final Fraction ONE_QUARTER

Fraction representation of 1/4.

TWO_QUARTERS

public static final Fraction TWO_QUARTERS

Fraction representation of 2/4.

THREE_QUARTERS

public static final Fraction THREE_QUARTERS

Fraction representation of 3/4.

ONE_FIFTH

public static final Fraction ONE_FIFTH

Fraction representation of 1/5.

TWO_FIFTHS

public static final Fraction TWO_FIFTHS

Fraction representation of 2/5.

THREE_FIFTHS

public static final Fraction THREE_FIFTHS

Fraction representation of 3/5.

FOUR_FIFTHS

public static final Fraction FOUR_FIFTHS

Fraction representation of 4/5.

Method Detail

getFraction

public static Fraction getFraction(int numerator,
                                   int denominator)

Creates a Fraction instance with the 2 parts of a fraction Y/Z.

Any negative signs are resolved to be on the numerator.

Parameters:

numerator - the numerator, for example the three in 'three sevenths'

denominator - the denominator, for example the seven in 'three sevenths'

Returns:

a new fraction instance

Throws:

ArithmeticException - if the denomiator is zero

getFraction

public static Fraction getFraction(int whole,
                                   int numerator,
                                   int denominator)

Creates a Fraction instance with the 3 parts of a fraction X Y/Z.

The negative sign must be passed in on the whole number part.

Parameters:

whole - the whole number, for example the one in 'one and three sevenths'

numerator - the numerator, for example the three in 'one and three sevenths'

denominator - the denominator, for example the seven in 'one and three sevenths'

Returns:

a new fraction instance

Throws:

ArithmeticException - if the denomiator is zero

ArithmeticException - if the denominator is negative

ArithmeticException - if the numerator is negative

ArithmeticException - if the resulting numerator exceeds Integer.MAX_VALUE

getReducedFraction

public static Fraction getReducedFraction(int numerator,
                                          int denominator)

Creates a reduced Fraction instance with the 2 parts of a fraction Y/Z.

For example, if the input parameters represent 2/4, then the created fraction will be 1/2.

Any negative signs are resolved to be on the numerator.

Parameters:

numerator - the numerator, for example the three in 'three sevenths'

denominator - the denominator, for example the seven in 'three sevenths'

Returns:

a new fraction instance, with the numerator and denominator reduced

Throws:

ArithmeticException - if the denominator is zero

getFraction

public static Fraction getFraction(double value)

Creates a Fraction instance from a double value.

This method uses the continued fraction algorithm, computing a maximum of 25 convergents and bounding the denominator by 10,000.

Parameters:

value - the double value to convert

Returns:

a new fraction instance that is close to the value

Throws:

ArithmeticException - if |value| > Integer.MAX_VALUE or value = NaN

ArithmeticException - if the calculated denominator is zero

ArithmeticException - if the the algorithm does not converge

getFraction

public static Fraction getFraction(String str)

Creates a Fraction from a String.

The formats accepted are:

1. double String containing a dot
2. 'X Y/Z'
3. 'Y/Z'
4. 'X' (a simple whole number)

and a .

Parameters:

str - the string to parse, must not be null

Returns:

the new Fraction instance

Throws:

IllegalArgumentException - if the string is null

NumberFormatException - if the number format is invalid

getNumerator

public int getNumerator()

Gets the numerator part of the fraction.

This method may return a value greater than the denominator, an improper fraction, such as the seven in 7/4.

Returns:

the numerator fraction part

getDenominator

public int getDenominator()

Gets the denominator part of the fraction.

Returns:

the denominator fraction part

getProperNumerator

public int getProperNumerator()

Gets the proper numerator, always positive.

An improper fraction 7/4 can be resolved into a proper one, 1 3/4. This method returns the 3 from the proper fraction.

If the fraction is negative such as -7/4, it can be resolved into -1 3/4, so this method returns the positive proper numerator, 3.

Returns:

the numerator fraction part of a proper fraction, always positive

getProperWhole

public int getProperWhole()

Gets the proper whole part of the fraction.

An improper fraction 7/4 can be resolved into a proper one, 1 3/4. This method returns the 1 from the proper fraction.

If the fraction is negative such as -7/4, it can be resolved into -1 3/4, so this method returns the positive whole part -1.

Returns:

the whole fraction part of a proper fraction, that includes the sign

intValue

public int intValue()

Gets the fraction as an int. This returns the whole number part of the fraction.

Specified by:

intValue in class Number

Returns:

the whole number fraction part

longValue

public long longValue()

Gets the fraction as a long. This returns the whole number part of the fraction.

Specified by:

longValue in class Number

Returns:

the whole number fraction part

floatValue

public float floatValue()

Gets the fraction as a float. This calculates the fraction as the numerator divided by denominator.

Specified by:

floatValue in class Number

Returns:

the fraction as a float

doubleValue

public double doubleValue()

Gets the fraction as a double. This calculates the fraction as the numerator divided by denominator.

Specified by:

doubleValue in class Number

Returns:

the fraction as a double

reduce

public Fraction reduce()

Reduce the fraction to the smallest values for the numerator and denominator, returning the result.

For example, if this fraction represents 2/4, then the result will be 1/2.

Returns:

a new reduced fraction instance, or this if no simplification possible

invert

public Fraction invert()

Gets a fraction that is the inverse (1/fraction) of this one.

The returned fraction is not reduced.

Returns:

a new fraction instance with the numerator and denominator inverted.

Throws:

ArithmeticException - if the fraction represents zero.

negate

public Fraction negate()

Gets a fraction that is the negative (-fraction) of this one.

The returned fraction is not reduced.

Returns:

a new fraction instance with the opposite signed numerator

abs

public Fraction abs()

Gets a fraction that is the positive equivalent of this one.

More precisely: (fraction >= 0 ? this : -fraction)

The returned fraction is not reduced.

Returns:

this if it is positive, or a new positive fraction instance with the opposite signed numerator

pow

public Fraction pow(int power)

Gets a fraction that is raised to the passed in power.

The returned fraction is in reduced form.

Parameters:

power - the power to raise the fraction to

Returns:

this if the power is one, ONE if the power is zero (even if the fraction equals ZERO) or a new fraction instance raised to the appropriate power

Throws:

ArithmeticException - if the resulting numerator or denominator exceeds Integer.MAX_VALUE

add

public Fraction add(Fraction fraction)

Adds the value of this fraction to another, returning the result in reduced form. The algorithm follows Knuth, 4.5.1.

Parameters:

fraction - the fraction to add, must not be null

Returns:

a Fraction instance with the resulting values

Throws:

IllegalArgumentException - if the fraction is null

ArithmeticException - if the resulting numerator or denominator exceeds Integer.MAX_VALUE

subtract

public Fraction subtract(Fraction fraction)

Subtracts the value of another fraction from the value of this one, returning the result in reduced form.

Parameters:

fraction - the fraction to subtract, must not be null

Returns:

a Fraction instance with the resulting values

Throws:

IllegalArgumentException - if the fraction is null

ArithmeticException - if the resulting numerator or denominator cannot be represented in an int.

multiplyBy

public Fraction multiplyBy(Fraction fraction)

Multiplies the value of this fraction by another, returning the result in reduced form.

Parameters:

fraction - the fraction to multiply by, must not be null

Returns:

a Fraction instance with the resulting values

Throws:

IllegalArgumentException - if the fraction is null

ArithmeticException - if the resulting numerator or denominator exceeds Integer.MAX_VALUE

divideBy

public Fraction divideBy(Fraction fraction)

Divide the value of this fraction by another.

Parameters:

fraction - the fraction to divide by, must not be null

Returns:

a Fraction instance with the resulting values

Throws:

IllegalArgumentException - if the fraction is null

ArithmeticException - if the fraction to divide by is zero

ArithmeticException - if the resulting numerator or denominator exceeds Integer.MAX_VALUE

equals

public boolean equals(Object obj)

Compares this fraction to another object to test if they are equal.

.

To be equal, both values must be equal. Thus 2/4 is not equal to 1/2.

Overrides:

equals in class Object

Parameters:

obj - the reference object with which to compare

Returns:

true if this object is equal

hashCode

public int hashCode()

Gets a hashCode for the fraction.

Overrides:

hashCode in class Object

Returns:

a hash code value for this object

compareTo

public int compareTo(Object object)

Compares this object to another based on size.

Note: this class has a natural ordering that is inconsistent with equals, because, for example, equals treats 1/2 and 2/4 as different, whereas compareTo treats them as equal.

Specified by:

compareTo in interface Comparable

Parameters:

object - the object to compare to

Returns:

-1 if this is less, 0 if equal, +1 if greater

Throws:

ClassCastException - if the object is not a Fraction

NullPointerException - if the object is null

toString

public String toString()

Gets the fraction as a String.

The format used is 'numerator/denominator' always.

Overrides:

toString in class Object

Returns:

a String form of the fraction

toProperString

public String toProperString()

Gets the fraction as a proper String in the format X Y/Z.

The format used in 'wholeNumber numerator/denominator'. If the whole number is zero it will be ommitted. If the numerator is zero, only the whole number is returned.

Returns:

a String form of the fraction