org.apache.commons.lang.math
Class Fraction

java.lang.Object
  extended byjava.lang.Number
      extended byorg.apache.commons.lang.math.Fraction
All Implemented Interfaces:
java.lang.Comparable, java.io.Serializable

public final class Fraction
extends java.lang.Number
implements java.lang.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 599500 2007-11-29 16:25:54Z mbenson $
Author:
Travis Reeder, Stephen Colebourne, 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(java.lang.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(java.lang.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(java.lang.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.
 java.lang.String toProperString()
          Gets the fraction as a proper String in the format X Y/Z.
 java.lang.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:
java.lang.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:
java.lang.ArithmeticException - if the denomiator is zero
java.lang.ArithmeticException - if the denominator is negative
java.lang.ArithmeticException - if the numerator is negative
java.lang.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:
java.lang.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:
java.lang.ArithmeticException - if |value| > Integer.MAX_VALUE or value = NaN
java.lang.ArithmeticException - if the calculated denominator is zero
java.lang.ArithmeticException - if the the algorithm does not converge

getFraction

public static Fraction getFraction(java.lang.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:
java.lang.IllegalArgumentException - if the string is null
java.lang.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.

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.

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.

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.

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:
java.lang.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:
java.lang.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:
java.lang.IllegalArgumentException - if the fraction is null
java.lang.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:
java.lang.IllegalArgumentException - if the fraction is null
java.lang.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:
java.lang.IllegalArgumentException - if the fraction is null
java.lang.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:
java.lang.IllegalArgumentException - if the fraction is null
java.lang.ArithmeticException - if the fraction to divide by is zero
java.lang.ArithmeticException - if the resulting numerator or denominator exceeds Integer.MAX_VALUE

equals

public boolean equals(java.lang.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.

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.

Returns:
a hash code value for this object

compareTo

public int compareTo(java.lang.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 java.lang.Comparable
Parameters:
object - the object to compare to
Returns:
-1 if this is less, 0 if equal, +1 if greater
Throws:
java.lang.ClassCastException - if the object is not a Fraction
java.lang.NullPointerException - if the object is null

toString

public java.lang.String toString()

Gets the fraction as a String.

The format used is 'numerator/denominator' always.

Returns:
a String form of the fraction

toProperString

public java.lang.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


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