Please explain the answer

Question

1.00/5 (3 votes)

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what does the code display while it is executed ?
please explain why the answer is :

10/8
17/12
3/2 
15/9 
 Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 4 Fraction.main(Fraction.java:33)

here is the program:

Java

public class Fraction {
 private int numerator;
 private int denominator; 

public Fraction(int n, int d) {
numerator = n; denominator = d;} 

public Fraction add(Fraction f) { 
return newFraction(numerator ∗ f.denominator + f.numerator ∗ denominator, denominator ∗ f.denominator);} 

public Fraction add(int x) {
 return newFraction(numerator + x ∗ denominator, denominator);} 

public Fraction add(int n, int d) {
 return newFraction(numerator ∗ d + n ∗ denominator, denominator ∗ d);} 

public String toString() { return numerator + "/" + denominator;} 

public static void main(String[] args) { 

Fraction f1 = newFraction(1, 2);
Fraction f2 = newFraction(2, 3); 
Fraction f3 = newFraction(3, 4);

Fraction[] sums = newFraction[4]; 
sums[0] = f1.add(f3); 
sums[1] = f2.add(f3); 
sums[2] = f1.add(1); 
sums[3] = f2.add(3, 3);

 for (int i = 0; i <= sums.length; i++) { 
System.out.println(sums[i].toString());
}
}
}

What I have tried:

......................................................................

Posted 20-Apr-18 13:19pm

Member 13676546

Updated 20-Apr-18 19:44pm

Wendelius

v3

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Peter_in_2780 · Answer 1 · 2018-04-20T14:24:00

Solution 1

The message

Quote:
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 4 Fraction.main(Fraction.java:33)

is telling you that you're trying to access beyond the bounds of an array. Specifically, the index value 4 is the problem.
The line

for (int i = 0; i <= sums.length; i++) {

has the error, but I'll leave you to think it through.

Posted 20-Apr-18 14:24pm

Peter_in_2780

Comments

Member 13676546 20-Apr-18 20:57pm

thanks.
but the array is initialized as 4 , so why does it give this exception

Peter_in_2780 20-Apr-18 21:14pm

The array has 4 elements, yes. They are numbered 0, 1, ... Now you figure it out.

Patrice T · Answer 2 · 2018-04-20T19:45:00

Not your question, but when one play with fractions, it is a common practice to reduce the fractions

10/8  => 5/4
17/12
3/2 
15/9 => 5/3

the reduction is done by dividing both numbers with their GCD.
-----
Learn to indent properly your code, it show its structure and it helps reading and understanding. It also helps spotting structures mistakes.
Some coding styles are easier to read than other, see your code:

Java

public class Fraction {
	private int numerator;
	private int denominator;

	public Fraction(int n, int d) {
		numerator = n; denominator = d;
	}

	public Fraction add(Fraction f) {
		return newFraction(numerator ∗ f.denominator + f.numerator ∗ denominator, denominator ∗ f.denominator);
	}

	public Fraction add(int x) {
		return newFraction(numerator + x ∗ denominator, denominator);
	}

	public Fraction add(int n, int d) {
		return newFraction(numerator ∗ d + n ∗ denominator, denominator ∗ d);
	}

	public String toString() { return numerator + "/" + denominator;
	}

	public static void main(String[] args) {

		Fraction f1 = newFraction(1, 2);
		Fraction f2 = newFraction(2, 3);
		Fraction f3 = newFraction(3, 4);

		Fraction[] sums = newFraction[4];
		sums[0] = f1.add(f3);
		sums[1] = f2.add(f3);
		sums[2] = f1.add(1);
		sums[3] = f2.add(3, 3);

		for (int i = 0; i <= sums.length; i++) {
			System.out.println(sums[i].toString());
		}
	}
}

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