Java - Can you please explain this code?

Question

public class P17 {
public static void main(String[] args) {
int[] v = { 1, 2, 3, 4 };
print(v);
fiddle(v, v[2] - 1);
print(v);
fiddle(v, v[2] - 1);
print(v);
}
public static void fiddle(int[] array, int idx) {
array[idx] = array[idx - 1] + 2;
}
public static void print(int[] array) {
System.out.print(array[0]);
for (int i = 1; i < array.length; i++)
System.out.print(", " + array[i]);
System.out.println();
}
}

Answer 1

Array (original values)
index |0 |1 |2 |3|
value |1 |2 |3 |4|

* First call to fiddle:
fiddle(v, v[2] - 1)
Knowing v[2] = 3 we know v[2] - 1 = 2
So we''ll pass 2 as idx argument to fiddle

* Inside fiddle (remember idx = 2)
array[idx] = array[idx - 1] + 2;
v[2] = v[1] + 2 meaning v[2] = 2 + 2
v[2] = 4

====================================

Array (values modified by first call)
index |0 |1 |2 |3|
value |1 |2 |4 |4|

* Second call to fiddle:
fiddle(v, v[2] - 1)
Knowing v[2] = 4 we know v[2] - 1 = 3
So we''ll pass 3 as idx argument to fiddle

* Inside fiddle (remember idx = 3)
array[idx] = array[idx - 1] + 2;
v[3] = v[2] + 2 meaning v[2] = 4 + 2
v[3] = 6

Hth, cmiiw

Answer 2

You're welcome! glad if it helps : )

Answer 3

Thank you for explanation, I truly appreciate your help!