Please explain this code....

Question

public class Program {
public static void main(String[] args) {
int [ ] myArr = {6, 42, 3, 7};
int sum=0;
for(int x=0; x<myArr.length; x++) {
sum += myArr[x];
}
System.out.println(sum);
}
}

Answer 1

You should focus on x's values in the for loop on this line:
for (int x=0; x<myArr.length; x++) {}

We know that myArr.length is 4, thus we can short it a little:
for (int x=0; x<4; x++) {}

These 3 statements say:
In the beginning x gets value 0.
Loop will continue iterating as long as x < 4 is true.
x gets incremented by 1 in each iteration.

We can conclude, that the loop breaks when x equals 4 and thus the loop will iterate 4 times for: x=0, x=1, x=2 & x=3.

In program it's not profitable to do so,
but we could split the for loop to:
int x;
x = 0;
sum += myArr[x];
x = 1;
sum += myArr[x];
x = 2;
sum += myArr[x];
x = 3;
sum += myArr[x];

And:
sum += myArr[0];
sum += myArr[1];
sum += myArr[2];
sum += myArr[3];

We know what are in myArr indices 0, 1, 2 and 3.

So we can minimize previous clip a little more.
sum += 6;
sum += 42;
sum += 3;
sum += 7;

Thus in the end sum will be:
sum = 6 + 42 + 3 + 7;

And thus sum = 58.

Answer 2

Seb TheS wow, that's a nice explanation👏👏👌