LISTING 13.13 1 public class Rational extends Number implements Comparable<Ratio

Question

LISTING 13.13

1 public class Rational extends Number implements Comparable<Rational> {
2 // Data fields for numerator and denominator
3 private long numerator = 0;
4 private long denominator = 1;
5
6 /** Construct a rational with default properties */
7 public Rational() {
8 this(0, 1);
9 }
10
11 /** Construct a rational with specified numerator and denominator */
12 public Rational(long numerator, long denominator) {
13 long gcd = gcd(numerator, denominator);
14 this.numerator = ((denominator > 0) ? 1 : -1) * numerator / gcd;
15 this.denominator = Math.abs(denominator) / gcd;
16 }
17
18 /** Find GCD of two numbers */
19 private static long gcd(long n, long d) {
20 long n1 = Math.abs(n);
21 long n2 = Math.abs(d);
22 int gcd = 1;
23
24 for (int k = 1; k <= n1 && k <= n2; k++) {
25 if (n1 % k == 0 && n2 % k == 0)
26 gcd = k;
27 }
28
29 return gcd;
30 }
31
32 /** Return numerator */
33 public long getNumerator() {
34 return numerator;
35 }
36
37 /** Return denominator */
38 public long getDenominator() {
39 return denominator;
40 }
41
42 /** Add a rational number to this rational */
43 public Rational add(Rational secondRational) {
44 long n = numerator * secondRational.getDenominator() +
45 denominator * secondRational.getNumerator();
46 long d = denominator * secondRational.getDenominator();
47 return new Rational(n, d);
48 }
49
50 /** Subtract a rational number from this rational */
51 public Rational subtract(Rational secondRational) {
52 long n = numerator * secondRational.getDenominator()
53 - denominator * secondRational.getNumerator();
54 long d = denominator * secondRational.getDenominator();
55 return new Rational(n, d);
56 }
57
58 /** Multiply a rational number by this rational */
59 public Rational multiply(Rational secondRational) {
60 long n = numerator * secondRational.getNumerator();
61 long d = denominator * secondRational.getDenominator();
62 return new Rational(n, d);
63 }
64
65 /** Divide a rational number by this rational */
66 public Rational divide(Rational secondRational) {
67 long n = numerator * secondRational.getDenominator();
68 long d = denominator * secondRational.numerator;
69 return new Rational(n, d);
70 }
71
72 @Override
73 public String toString() {
74 if (denominator == 1)
75 return numerator + "";
76 else
77 return numerator + "/" + denominator;
78 }
79
80 @Override // Override the equals method in the Object class
81 public boolean equals(Object other) {
82 if ((this.subtract((Rational)(other))).getNumerator() == 0)
83 return true;
84 else
85 return false;
86 }
87
88 @Override // Implement the abstract intValue method in Number
89 public int intValue() {
a
b + c
d = ad + bc
bd
a
b - c
d = ad - bc
bd
a
b * c
d = ac
bd
a
b , c
d = ad
bc
13.9 Case Study: The Rational Class 523
524 Chapter 13 Abstract Classes and Interfaces
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 }

13.14 (Demonstrate the benefits of encapsulation) Rewrite the Rational class in Listing 13.13 using a new internal representation for the numerator and denomina- tor. Create an array of two integers as follows: private long]r new long[ 2] Use r[0] to represent the numerator and r[1] to represent the denominator. The signatures of the methods in the Rational class are not changed, so a client application that uses the previous Rational class can continue to use this new Rational class without being recompiled.

Explanation / Answer

public class Rational extends Number implements Comparable<Rational> {
// Data fields for numerator and denominator
private long[] r= new long[2];

/** Construct a rational with default properties */
public Rational() {
this(0, 1);
}

/** Construct a rational with specified numerator and denominator */
public Rational(long numerator, long denominator) {
long gcd = gcd(numerator, denominator);
this.r[0] = ((denominator > 0) ? 1 : -1) * numerator / gcd;
this.r[1] = Math.abs(denominator) / gcd;
}

/** Find GCD of two numbers */
private static long gcd(long n, long d) {
long n1 = Math.abs(n);
long n2 = Math.abs(d);
int gcd = 1;

for (int k = 1; k <= n1 && k <= n2; k++) {
if (n1 % k == 0 && n2 % k == 0)
gcd = k;
}

return gcd;
}

/** Return numerator */
public long getNumerator() {
return this.r[0];
}

/** Return denominator */
public long getDenominator() {
return this.r[1];
}

/** Add a rational number to this rational */
public Rational add(Rational secondRational) {
long n = this.r[0] * secondRational.getDenominator() + this.r[1]* secondRational.getNumerator();
long d = this.r[1] * secondRational.getDenominator();
return new Rational(n, d);
}

/** Subtract a rational number from this rational */
public Rational subtract(Rational secondRational) {
long n = this.getNumerator() * secondRational.getDenominator() - this.getDenominator() * secondRational.getNumerator();
long d = this.getDenominator() * secondRational.getDenominator();
return new Rational(n, d);
}

/** Multiply a rational number by this rational */
public Rational multiply(Rational secondRational) {
long n = this.getNumerator() * secondRational.getNumerator();
long d = this.getDenominator() * secondRational.getDenominator();
return new Rational(n, d);
}

/** Divide a rational number by this rational */
public Rational divide(Rational secondRational) {
long n = this.getNumerator() * secondRational.getDenominator();
long d = this.getDenominator() * secondRational.getNumerator();
return new Rational(n, d);
}

@Override
public String toString() {
if (this.getDenominator() == 1)
return this.getNumerator() + "";
else
return this.getNumerator() + "/" + this.getDenominator();
}

@Override
// Override the equals method in the Object class
public boolean equals(Object other) {
if ((this.subtract((Rational) (other))).getNumerator() == 0)
return true;
else
return false;
}

@Override
// Implement the abstract intValue method in Number
public int intValue() {
return (int) doubleValue();
}

@Override
// Implement the abstract floatValue method in Number
public float floatValue() {
return (float) doubleValue();
}

@Override
// Implement the doubleValue method in Number
public double doubleValue() {
return this.getNumerator() * 1.0 / this.getDenominator();
}

@Override
// Implement the abstract longValue method in Number
public long longValue() {
return (long) doubleValue();
}

@Override
// Implement the compareTo method in Comparable
public int compareTo(Rational o) {
if (this.subtract(o).getNumerator() > 0)
return 1;
else if (this.subtract(o).getNumerator() < 0)
return -1;
else
return 0;
}
}

Here is the code after changing numerator denominator as per requriement

Advice: Try putting code without numbers.

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