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It compares the adjacent elements and swaps until the sorting is achieved.

For example,

int[] num= {90,24,46,35,32};

Lets see how bubble sort works

First round:

90,24,46,35,32
24,90,46,35,32
24,46,90,35,32
24,46,35,90,32
24,46,35,32,90

Second round:

24,46,35,32,90
24,35,46,32,90
24,35,32,46,90

Third round:

24,35,32,46,90
24,32,35,46,90

That's it after 3 rounds of adjacent element comparison we have achieved the sorted order using Bubble sort.

Let's start coding for bubble sort,

package com.praveen.sort;

import java.util.Arrays;

public class BubbleSort {

	public static void main(String[] args) {
		int[] arr = { 90, 24, 46, 35, 32 };
		bubble(arr);
		System.out.println(Arrays.toString(arr));
	}

	private static void bubble(int[] arr) {
		boolean swapped;
		// run the steps n-1 times
		for (int i = 0; i < arr.length; i++) {
			swapped = false;
			// for each step, max item will come at the last respective index
			for (int j = 1; j < arr.length - i; j++) {
				// swap if the item is smaller than the previous item
				if (arr[j] < arr[j - 1]) {
					// swap
					int temp = arr[j];
					arr[j] = arr[j - 1];
					arr[j - 1] = temp;
					swapped = true;
				}
			}
			// if you did not swap for a particular value of i, it means the array is sorted
			// hence stop the program
			if (!swapped) { // !false = true
				break;
			}
		}
	}

}

Output

[24, 32, 35, 46, 90]