Can Someone explain this to me please

Estimate the order of growth for the following methods.

1.

// Method 1

public static int getSum(int[] arr) {

int sum = 0;

int n = arr.length;

for (int i = 0; i < n; i++) {

sum += arr[i];

}

return sum;

}

2.

// Method

2

public static int getSum(int[] arr) {

int sum = 0;

int n = arr.length;

for (int i = 1; i < n; i *= 3) {

sum += arr[i];

}

return sum;

}

3. /

/ Method 5

public static int getSum(int[] arr) {

int sum = 0;

int n = arr.length;

for (int i = 2; i < n; i *= 2) {

sum += arr[i];

}

return sum;

}