BubbleSort.java

package Arrays.Sorting;

public class BubbleSort {
    /*
     * This method takes a int array as input
     * Then sorts the array using BUBBLE SORT algorithm
     * Then returns the sorted array
     */
    public static int[] sort(int[] arr) {
        int n = arr.length;

        for (int i = 0; i < n; i++) {
            for (int j = 0; j < n - 1; j++) {
                if (arr[j] > arr[j + 1]) {
                    int temp = arr[j];
                    arr[j] = arr[j + 1];
                    arr[j + 1] = temp;
                }
            }
        }
        return arr;
    }
}

Bubble Sort

it is the simplest sorting algorithm that works by repeatedly swapping the adjacent elements if they are in the wrong order. This algorithm is not suitable for large data sets as its average and worst-case time complexity is quite high.

Input: arr[] = {5, 1, 4, 2, 8}

First Pass:

Bubble sort starts with very first two elements, comparing them to check which one is greater.
    ( 5 1 4 2 8 ) –> ( 1 5 4 2 8 ), Here, algorithm compares the first two elements, and swaps since 5 > 1. 
    ( 1 5 4 2 8 ) –>  ( 1 4 5 2 8 ), Swap since 5 > 4 
    ( 1 4 5 2 8 ) –>  ( 1 4 2 5 8 ), Swap since 5 > 2 
    ( 1 4 2 5 8 ) –> ( 1 4 2 5 8 ), Now, since these elements are already in order (8 > 5), algorithm does not swap them.

Second Pass:

Now, during second iteration it should look like this:
    ( 1 4 2 5 8 ) –> ( 1 4 2 5 8 ) 
    ( 1 4 2 5 8 ) –> ( 1 2 4 5 8 ), Swap since 4 > 2 
    ( 1 2 4 5 8 ) –> ( 1 2 4 5 8 ) 
    ( 1 2 4 5 8 ) –>  ( 1 2 4 5 8 )