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Rational

public final class Rational
extends Number implements Comparable<Rational>

java.lang.Object
   ↳ java.lang.Number
     ↳ android.util.Rational


An immutable data type representation a rational number.

Contains a pair of ints representing the numerator and denominator of a Rational number.

Summary

Fields

public static final Rational NEGATIVE_INFINITY

Constant for the negative infinity value of the Rational type.

public static final Rational NaN

Constant for the Not-a-Number (NaN) value of the Rational type.

public static final Rational POSITIVE_INFINITY

Constant for the positive infinity value of the Rational type.

public static final Rational ZERO

Constant for the zero value of the Rational type.

Public constructors

Rational(int numerator, int denominator)

Create a Rational with a given numerator and denominator.

Public methods

int compareTo(Rational another)

Compare this rational to the specified rational to determine their natural order.

double doubleValue()

Returns the value of the specified number as a double.

boolean equals(Object obj)

Compare this Rational to another object and see if they are equal.

float floatValue()

Returns the value of the specified number as a float.

int getDenominator()

Gets the denominator of the rational

The denominator may return 0, in which case the rational may represent positive infinity (if the numerator was positive), negative infinity (if the numerator was negative), or NaN (if the numerator was 0).

int getNumerator()

Gets the numerator of the rational.

int hashCode()

Returns a hash code value for the object.

int intValue()

Returns the value of the specified number as a int.

boolean isFinite()

Indicates whether this rational represents a finite value.

boolean isInfinite()

Indicates whether this rational represents an infinite value.

boolean isNaN()

Indicates whether this rational is a Not-a-Number (NaN) value.

boolean isZero()

Indicates whether this rational represents a zero value.

long longValue()

Returns the value of the specified number as a long.

static Rational parseRational(String string)

Parses the specified string as a rational value.

short shortValue()

Returns the value of the specified number as a short.

String toString()

Return a string representation of this rational, e.g.

Inherited methods

From class java.lang.Number
From class java.lang.Object
From interface java.lang.Comparable

Fields

NEGATIVE_INFINITY

added in API level 21
Rational NEGATIVE_INFINITY

Constant for the negative infinity value of the Rational type.

Equivalent to constructing a new rational with a negative numerator and a denominator equal to 0.

NaN

added in API level 21
Rational NaN

Constant for the Not-a-Number (NaN) value of the Rational type.

A NaN value is considered to be equal to itself (that is NaN.equals(NaN) will return true; it is always greater than any non-NaN value (that is NaN.compareTo(notNaN) will return a number greater than 0).

Equivalent to constructing a new rational with both the numerator and denominator equal to 0.

POSITIVE_INFINITY

added in API level 21
Rational POSITIVE_INFINITY

Constant for the positive infinity value of the Rational type.

Equivalent to constructing a new rational with a positive numerator and a denominator equal to 0.

ZERO

added in API level 21
Rational ZERO

Constant for the zero value of the Rational type.

Equivalent to constructing a new rational with a numerator equal to 0 and any non-zero denominator.

Public constructors

Rational

added in API level 21
Rational (int numerator, 
                int denominator)

Create a Rational with a given numerator and denominator.

The signs of the numerator and the denominator may be flipped such that the denominator is always positive. Both the numerator and denominator will be converted to their reduced forms (see equals(Object) for more details).

For example,

  • a rational of 2/4 will be reduced to 1/2.
  • a rational of 1/-1 will be flipped to -1/1
  • a rational of 5/0 will be reduced to 1/0
  • a rational of 0/5 will be reduced to 0/1

Parameters
numerator int: the numerator of the rational

denominator int: the denominator of the rational

See also:

Public methods

compareTo

added in API level 21
int compareTo (Rational another)

Compare this rational to the specified rational to determine their natural order.

NaN is considered to be equal to itself and greater than all other Rational values. Otherwise, if the objects are not equal, then the following rules apply:

  • Positive infinity is greater than any other finite number (or negative infinity)
  • Negative infinity is less than any other finite number (or positive infinity)
  • The finite number represented by this rational is checked numerically against the other finite number by converting both rationals to a common denominator multiple and comparing their numerators.

Parameters
another Rational: the rational to be compared

Returns
int a negative integer, zero, or a positive integer as this object is less than, equal to, or greater than the specified rational.

Throws
NullPointerException if another was null

doubleValue

added in API level 21
double doubleValue ()

Returns the value of the specified number as a double.

The double is calculated by converting both the numerator and denominator to a double; then returning the result of dividing the numerator by the denominator.

Returns
double the divided value of the numerator and denominator as a double.

equals

added in API level 21
boolean equals (Object obj)

Compare this Rational to another object and see if they are equal.

A Rational object can only be equal to another Rational object (comparing against any other type will return false).

A Rational object is considered equal to another Rational object if and only if one of the following holds:

  • Both are NaN
  • Both are infinities of the same sign
  • Both have the same numerator and denominator in their reduced form

A reduced form of a Rational is calculated by dividing both the numerator and the denominator by their greatest common divisor.

(new Rational(1, 2)).equals(new Rational(1, 2)) == true   // trivially true
 (new Rational(2, 3)).equals(new Rational(1, 2)) == false  // trivially false
 (new Rational(1, 2)).equals(new Rational(2, 4)) == true   // true after reduction
 (new Rational(0, 0)).equals(new Rational(0, 0)) == true   // NaN.equals(NaN)
 (new Rational(1, 0)).equals(new Rational(5, 0)) == true   // both are +infinity
 (new Rational(1, 0)).equals(new Rational(-1, 0)) == false // +infinity != -infinity
 

Parameters
obj Object: a reference to another object

Returns
boolean A boolean that determines whether or not the two Rational objects are equal.

floatValue

added in API level 21
float floatValue ()

Returns the value of the specified number as a float.

The float is calculated by converting both the numerator and denominator to a float; then returning the result of dividing the numerator by the denominator.

Returns
float the divided value of the numerator and denominator as a float.

getDenominator

added in API level 21
int getDenominator ()

Gets the denominator of the rational

The denominator may return 0, in which case the rational may represent positive infinity (if the numerator was positive), negative infinity (if the numerator was negative), or NaN (if the numerator was 0).

The denominator will always return 1 if the numerator is 0.

Returns
int

getNumerator

added in API level 21
int getNumerator ()

Gets the numerator of the rational.

The numerator will always return 1 if this rational represents infinity (that is, the denominator is 0).

Returns
int

hashCode

added in API level 21
int hashCode ()

Returns a hash code value for the object. This method is supported for the benefit of hash tables such as those provided by HashMap.

The general contract of hashCode is:

  • Whenever it is invoked on the same object more than once during an execution of a Java application, the hashCode method must consistently return the same integer, provided no information used in equals comparisons on the object is modified. This integer need not remain consistent from one execution of an application to another execution of the same application.
  • If two objects are equal according to the equals(Object) method, then calling the hashCode method on each of the two objects must produce the same integer result.
  • It is not required that if two objects are unequal according to the equals(java.lang.Object) method, then calling the hashCode method on each of the two objects must produce distinct integer results. However, the programmer should be aware that producing distinct integer results for unequal objects may improve the performance of hash tables.

As much as is reasonably practical, the hashCode method defined by class Object does return distinct integers for distinct objects. (This is typically implemented by converting the internal address of the object into an integer, but this implementation technique is not required by the Java™ programming language.)

Returns
int a hash code value for this object.

intValue

added in API level 21
int intValue ()

Returns the value of the specified number as a int.

Finite rationals are converted to an int value by dividing the numerator by the denominator; conversion for non-finite values happens identically to casting a floating point value to an int, in particular:

  • Positive infinity saturates to the largest maximum integer MAX_VALUE
  • Negative infinity saturates to the smallest maximum integer MIN_VALUE
  • Not-A-Number (NaN) returns 0.

Returns
int the divided value of the numerator and denominator as a int.

isFinite

added in API level 21
boolean isFinite ()

Indicates whether this rational represents a finite value.

A finite value occurs when the denominator is not 0; in other words the rational is neither infinity or NaN.

Returns
boolean true if this rational is a (positive or negative) infinite value; false if this is a finite number value (or NaN)

isInfinite

added in API level 21
boolean isInfinite ()

Indicates whether this rational represents an infinite value.

An infinite value occurs when the denominator is 0 (but the numerator is not).

Returns
boolean true if this rational is a (positive or negative) infinite value; false if this is a finite number value (or NaN)

isNaN

added in API level 21
boolean isNaN ()

Indicates whether this rational is a Not-a-Number (NaN) value.

A NaN value occurs when both the numerator and the denominator are 0.

Returns
boolean true if this rational is a Not-a-Number (NaN) value; false if this is a (potentially infinite) number value

isZero

added in API level 21
boolean isZero ()

Indicates whether this rational represents a zero value.

A zero value is a finite rational with a numerator of 0.

Returns
boolean true if this rational is finite zero value; false otherwise

longValue

added in API level 21
long longValue ()

Returns the value of the specified number as a long.

Finite rationals are converted to an long value by dividing the numerator by the denominator; conversion for non-finite values happens identically to casting a floating point value to a long, in particular:

  • Positive infinity saturates to the largest maximum long MAX_VALUE
  • Negative infinity saturates to the smallest maximum long MIN_VALUE
  • Not-A-Number (NaN) returns 0.

Returns
long the divided value of the numerator and denominator as a long.

parseRational

added in API level 21
Rational parseRational (String string)

Parses the specified string as a rational value.

The ASCII characters \u003a (':') and \u002f ('/') are recognized as separators between the numerator and denumerator.

For any Rational r: Rational.parseRational(r.toString()).equals(r). However, the method also handles rational numbers expressed in the following forms:

"num/den" or "num:den" => new Rational(num, den);, where num and den are string integers potentially containing a sign, such as "-10", "+7" or "5".

Rational.parseRational("3:+6").equals(new Rational(1, 2)) == true
 Rational.parseRational("-3/-6").equals(new Rational(1, 2)) == true
 Rational.parseRational("4.56") => throws NumberFormatException
 

Parameters
string String: the string representation of a rational value.

Returns
Rational the rational value represented by string.

Throws
NumberFormatException if string cannot be parsed as a rational value.
NullPointerException if string was null

shortValue

added in API level 21
short shortValue ()

Returns the value of the specified number as a short.

Finite rationals are converted to a short value identically to intValue(); the int result is then truncated to a short before returning the value.

Returns
short the divided value of the numerator and denominator as a short.

toString

added in API level 21
String toString ()

Return a string representation of this rational, e.g. "1/2".

The following rules of conversion apply:

  • NaN values will return "NaN"
  • Positive infinity values will return "Infinity"
  • Negative infinity values will return "-Infinity"
  • All other values will return "numerator/denominator" where numerator and denominator are substituted with the appropriate numerator and denominator values.

Returns
String a string representation of the object.

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