Using a For Loop to Manually Sort an Array - Java

Question

I'm having trouble manually sorting the array with a for loop. It works except for the first and last number. Here's my code:

Scanner numInput = new Scanner(System.in);

int tempVar, num;
String numbersString;
int[] numbers = {4, 11, 13, 12, 17, 35, 15, 7, 19, 3, 45};

for (int i = 0; i < numbers.length - 1; i++)
{
  for(int j = 0; j < numbers.length - 1; j++)
  {
    if(numbers[i] < numbers[j + 1])
    {
      tempVar = numbers [j + 1];
      numbers [j + 1]= numbers [i];
      numbers [i] = tempVar;
    }
  }
} 

numbersString = Arrays.toString(numbers);

System.out.println(numbersString);

Answer 1

You have to initialize the value for j as i+1, this sorting algorithm is called bubble sort, that works by repeatedly swapping the adjacent elements if they are in wrong order. The below method is always runs O(n^2) time even if the array is sorted.

public static void main (String[] args)
{
    int[] array = {4,2,1,3,5,9,6,8,7};

    for(int i = 0 ; i < array.length;i++)
    {
        for(int j = i+1 ; j< array.length;j++)
        {
            if(array[i] > array[j])
            {
                int temp = array[i];
                array[i] = array[j];
                array[j] = temp;
            }
        }
    }