ABSTRACT CLASSES AND INTERFACES - Introduction to Java Programming - page 588

83 return true ;

84 else

85 return false ;

86 }
87
88 @Override // Implement the abstract intValue method in Number
89

public int intValue() {

90 return ( int )doubleValue();

91 }
92
93 @Override // Implement the abstract floatValue method in Number
94 public float floatValue() {

95 return ( float )doubleValue();

96 }
97
98 @Override // Implement the doubleValue method in Number
99

public double doubleValue() {

100 return numerator * 1.0 / denominator;

101 }
102
103 @Override // Implement the abstract longValue method in Number
104 public long longValue() {

105 return ( long )doubleValue();

106 }
107
108 @Override // Implement the compareTo method in Comparable
109

public int compareTo(Rational o) {

110 if ( this .subtract(o).getNumerator() > 0 )

111 return 1 ;

112 else if ( this .subtract(o).getNumerator() < 0 )

113 return -1 ;

114 else

115 return 0 ;

116 }
117 }

The rational number is encapsulated in a Rational object. Internally, a rational number is
represented in its lowest terms (line 13), and the numerator determines its sign (line 14). The
denominator is always positive (line 15).
The gcd method (lines 19-30 in the Rational class) is private; it is not intended for use
by clients. The gcd method is only for internal use by the Rational class. The gcd method
is also static, since it is not dependent on any particular Rational object.
The abs(x) method (lines 20-21 in the Rational class) is defined in the Math class and
returns the absolute value of x .
Two Rational objects can interact with each other to perform add, subtract, multiply, and
divide operations. These methods return a new Rational object (lines 43-70).
The methods toString and equals in the Object class are overridden in the Rational
class (lines 72-86). The toString() method returns a string representation of a Rational
object in the form numerator/denominator , or simply numerator if denominator is 1 .
The equals(Object other) method returns true if this rational number is equal to the
other rational number.
The abstract methods intValue , longValue , floatValue , and doubleValue in the
Number class are implemented in the Rational class (lines 88-106). These methods return
the int , long , float , and double value for this rational number.
The compareTo(Rational other) method in the Comparable interface is imple-
mented in the Rational class (lines 108-116) to compare this rational number to the other
rational number.