Class Fraction

java.lang.Object
java.lang.Number
org.apache.commons.lang3.math.Fraction
All Implemented Interfaces:
Serializable, Comparable<Fraction>
public final class Fraction extends Number implements Comparable<Fraction>
Fraction is a Number implementation that stores fractions accurately.

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

Note that this class is intended for common use cases, it is int based and thus suffers from various overflow issues. For a BigInteger based equivalent, please see the Commons Math BigFraction class.

Since:
2.0
See Also:

  • Field Details

  • Method Details

    • getFraction

      public static Fraction getFraction(double value)
      Gets 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 - Thrown if |value| &gt; Integer.MAX_VALUE or value = NaN.
      ArithmeticException - Thrown if the calculated denominator is zero.
      ArithmeticException - Thrown if the algorithm does not converge.

    • getFraction

      public static Fraction getFraction(int numerator, int denominator)
      Gets 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 - Thrown if the denominator is zero or the denominator is negative and the numerator is Integer#MIN_VALUE.

    • getFraction

      public static Fraction getFraction(int whole, int numerator, int denominator)
      Gets 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 - Thrown if the denominator is zero.
      ArithmeticException - Thrown if the denominator is negative.
      ArithmeticException - Thrown if the numerator is negative.
      ArithmeticException - Thrown if the resulting numerator exceeds Integer.MAX_VALUE.

    • getFraction

      public static Fraction getFraction(String str)
      Gets 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:
      NullPointerException - Thrown if the string is null
      NumberFormatException - Thrown if the number format is invalid, or if the string is well-formed but its value cannot be represented as a Fraction: a zero denominator such as "1/0", a value outside the range of an int such as "9999999999.5", or a mixed number whose combined numerator overflows. For those unrepresentable values, the causal ArithmeticException is preserved as the cause.

    • getReducedFraction

      public static Fraction getReducedFraction(int numerator, int denominator)
      Gets 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 - Thrown if the denominator is zero, or the reduced numerator or positive denominator cannot be represented as an int.

    • abs

      public Fraction abs()
      Gets a fraction that is the positive equivalent of this one.

      More precisely: (fraction &gt;= 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

    • 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:
      NullPointerException - Thrown if the fraction is null.
      ArithmeticException - Thrown if the resulting numerator or denominator exceeds Integer.MAX_VALUE.

    • compareTo

      public int compareTo(Fraction other)
      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<Fraction>
      Parameters:
      other - The object to compare to
      Returns:
      -1 if this is less, 0 if equal, +1 if greater
      Throws:
      ClassCastException - Thrown if the object is not a Fraction.
      NullPointerException - Thrown if the object is null.

    • 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:
      NullPointerException - Thrown if the fraction is null.
      ArithmeticException - Thrown if the fraction to divide by is zero.
      ArithmeticException - Thrown if the resulting numerator or denominator exceeds Integer.MAX_VALUE.

    • 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

    • 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

    • 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

    • getDenominator

      public int getDenominator()
      Gets the denominator part of the fraction.
      Returns:
      The denominator fraction part

    • 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

    • 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

    • hashCode

      public int hashCode()
      Gets a hashCode for the fraction.
      Overrides:
      hashCode in class Object
      Returns:
      A hash code value for this object

    • 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

    • 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 - Thrown if the fraction represents zero.

    • 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

    • 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:
      NullPointerException - Thrown if the fraction is null.
      ArithmeticException - Thrown if the resulting numerator or denominator exceeds Integer.MAX_VALUE.

    • 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

    • 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 - Thrown if the resulting numerator or denominator exceeds Integer.MAX_VALUE.

    • 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

    • 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:
      NullPointerException - Thrown if the fraction is null.
      ArithmeticException - Thrown if the resulting numerator or denominator cannot be represented in an int.

    • 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 omitted. If the numerator is zero, only the whole number is returned.

      Returns:
      A String form of the fraction

    • 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