edu.cmu.cs.pattis.cs151xx
Class Rational

java.lang.Object
  edu.cmu.cs.pattis.cs151xx.Rational

public class Rational
extends java.lang.Object

Objects constructed from the Rational class act like fractions (rational numbers have a sign, numerator, and denominator). This class implements some standard arithemetic and relational operations (as methods) on values of this class. Object constructed from this class obey the following class invariants

• Zero is always stored as 0/1
• Denominators are always positive
• Numerators and Denominators are in lowest common terms (they have no common factors)

Note that objcets constructed from this class are immutable, so once these invariants are satisfied by the constructor, they always stay true.

Field Summary

static Rational	ONE Stores the fraction 1/1.
static Rational	ZERO Stores the fraction 0/1.

Constructor Summary

Rational()
Constructs a Rational object 0/1.

Rational(int numerator)
Constructs a Rational object, specifying the numerator of the fraction (the denominator is one).

Rational(int numerator, int denominator)
Constructs a Rational object, specifying the numerator and denominator of the fraction.

Rational(Rational other)
Constructs a Rational object whose state is the same as other.

Method Summary

Rational	abs() Returns a new fraction that is the absolute value of this one.
Rational	add(Rational other) Returns a new fraction that is the sum of this one and other.
int	compareTo(Rational other) Returns the trichotomous comparison of this value and other.
Rational	divide(Rational other) Returns a new fraction that is the dividend of this one and other.
boolean	equals(Rational other) Returns whether or not this fraction is equal to other.
int	getDenominator() Returns the denominator of the fraction.
int	getNumerator() Returns the numerator of the fraction.
Rational	multiply(Rational other) Returns a new fraction that is the product of this one and other.
Rational	negate() Returns a new fraction that is the negated value of this one.
static Rational	prompt(java.lang.String message) Returns a new fraction after prompting the user for its numerator and denominator.
Rational	reciprocal() Returns a new fraction that is the reciprocal value of this one: 1/this.
Rational	subtract(Rational other) Returns a new fraction that is the difference of this one and other.
java.lang.String	toDecimalString(int decimalPlaces) Returns a String representation of the state of this fraction, as a decimal value approximating the fraction.
java.lang.String	toString() Returns a String representation of the state of this fraction: numerator/denominator.

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

ZERO

public static final Rational ZERO

Stores the fraction 0/1.

ONE

public static final Rational ONE

Stores the fraction 1/1.

Constructor Detail

Rational

public Rational(int numerator,
                int denominator)
         throws java.lang.IllegalArgumentException

Constructs a Rational object, specifying the numerator and denominator of the fraction. These value are examined and put in a canonical form to ensure the following class invariants

• Zero is always stored as 0/1
• Denominators are always positive
• Numerators and Denominators are in lowest common terms (they have no common factors)

Parameters:

numerator - specifies the numerator of the fraction

denominator - specifies the denominator of the fraction

Throws:

java.lang.IllegalArgumentException - if denominator is 0

Rational

public Rational(int numerator)

Constructs a Rational object, specifying the numerator of the fraction (the denominator is one).

Parameters:

numerator - specifies the numerator of the fraction

Rational

public Rational()

Constructs a Rational object 0/1.

Rational

public Rational(Rational other)

Constructs a Rational object whose state is the same as other.

Parameters:

other - specifies the fraction whose value to store into the state of this object

Method Detail

getNumerator

public int getNumerator()

Returns the numerator of the fraction.

Returns:

the numerator of the fraction

getDenominator

public int getDenominator()

Returns the denominator of the fraction.

Returns:

the denominator of the fraction

equals

public boolean equals(Rational other)

Returns whether or not this fraction is equal to other.

Parameters:

other - specifies the other fraction in the equality check

Returns:

whether or not this fraction is equal to other

compareTo

public int compareTo(Rational other)

Returns the trichotomous comparison of this value and other. More specifically:

• a negative value if this < other
• zero if this = other
• a positive value if this > other

Example use, checking whether f1 is less than or equal to f2:

  if (f1.compareTo(f2) <= 0)

Parameters:

other - specifies the other fraction in the comparison

Returns:

the trichotomous comparison of this value and other

abs

public Rational abs()

Returns a new fraction that is the absolute value of this one.

Returns:

a new fraction that is the absolute value of this one.

negate

public Rational negate()

Returns a new fraction that is the negated value of this one.

Returns:

a new fraction that is the negated value of this one.

reciprocal

public Rational reciprocal()
                    throws java.lang.IllegalStateException

Returns a new fraction that is the reciprocal value of this one: 1/this.

Returns:

a new fraction that is the reciprocal value of this one: 1/this

Throws:

java.lang.IllegalStateException - if this value is 0

add

public Rational add(Rational other)

Returns a new fraction that is the sum of this one and other.

Parameters:

other - specifies the other fraction in the sum

Returns:

a new fraction that is the sum of this one and other

subtract

public Rational subtract(Rational other)

Returns a new fraction that is the difference of this one and other.

Parameters:

other - specifies the other fraction in the difference

Returns:

a new fraction that is the difference of this one and other

multiply

public Rational multiply(Rational other)

Returns a new fraction that is the product of this one and other.

Parameters:

other - specifies the other fraction in the product

Returns:

a new fraction that is the product of this one and other

divide

public Rational divide(Rational other)
                throws java.lang.IllegalArgumentException

Returns a new fraction that is the dividend of this one and other.

Parameters:

other - specifies the other fraction in the division

Returns:

a new fraction that is the dividend of this one and other

Throws:

java.lang.IllegalArgumentException - if other value is 0

toString

public java.lang.String toString()

Returns a String representation of the state of this fraction: numerator/denominator.

Overrides:

toString in class java.lang.Object

Returns:

a String representation of the state of this fraction: numerator/denominator

toDecimalString

public java.lang.String toDecimalString(int decimalPlaces)

Returns a String representation of the state of this fraction, as a decimal value approximating the fraction. For example (new Rational(1,3)).toDecimalString(20) returns ".33333333333333333333"; (new Rational(1,7)).toDecimalString(13) returns ".1428571428571".

Parameters:

decimalPlaces - specifies the number of decimal places to use in the approximation

Returns:

a String representation of the state of this fraction, as a decimal value approximating the fraction

prompt

public static Rational prompt(java.lang.String message)

Returns a new fraction after prompting the user for its numerator and denominator. If an illegal value is entered, the user is reprompted For example, if we write Rational.prompt("Enter height") an interaction on the console screen might look like

  Enter Height
    Enter numerator  : 1
    Enter denominator: 3

Parameters:

message - specifies the message with which to prompt the user

Returns:

a new fraction after prompting the user for its numerator and denominator.