Bubble Sort Java: A Simple and Efficient Sorting Algorithm

Bubble Sort in Java: A Simple and Efficient Sorting Algorithm

If you are looking for a simple and efficient way to sort an array of elements in Java, you might want to consider bubble sort. Bubble sort is one of the most straightforward sorting algorithms that works by repeatedly swapping the adjacent elements if they are in the wrong order until the array is sorted.

bubble sort java

What is Bubble Sort?

Bubble sort is a comparison-based sorting algorithm that compares each pair of adjacent elements in an array and swaps them if they are in the wrong order. The algorithm repeats this process until no more swaps are needed, which means that the array is sorted.

How does it work?

To understand how bubble sort works, let's take an example of an array of integers that we want to sort in ascending order:

int[] arr = 4, 2, 1, 6, 3, 5;

We start by comparing the first two elements, 4 and 2. Since 4 is greater than 2, we swap them:

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int[] arr = 2, 4, 1, 6, 3, 5;

Then we compare the next pair of elements, 4 and 1. Again, we swap them since 4 is greater than 1:

int[] arr = 2, 1, 4, 6, 3, 5;

We keep doing this for the rest of the elements until we reach the end of the array:

int[] arr = 2, 1, 4, 6, 3, 5; int[] arr = 2, 1, 4, 3, 6, 5; int[] arr = 2, 1, 4, 3, 5, 6;

At this point, we have completed one iteration of the algorithm. We can see that the last element, 6, is now in its correct position. We can also see that the array is not fully sorted yet. Therefore, we need to repeat the same process for the remaining elements, excluding the last one.

In general, for an array of size n, we need to perform n-1 iterations of the algorithm. In each iteration, we compare and swap each pair of adjacent elements until we reach the end of the unsorted part of the array. As a result, after each iteration, one more element will be in its correct position at the end of the array.

The following table shows how the array changes after each iteration:

IterationArray

0 (initial)4, 2, 1, 6, 3, 5

12, 1, 4, 3, 5, 6

style="color:red">3, 4, 5, 6}

31, 2, 3, 4, 5, 6

41, 2, 3, 4, 5, 6

5 (final)1, 2, 3, 4, 5, 6

What are the advantages and disadvantages of bubble sort?

Bubble sort has some advantages and disadvantages that you should be aware of before using it. Here are some of them:

Advantages:

• Bubble sort is easy to understand and implement.

• Bubble sort does not require any extra space, as it sorts the array in place.

• Bubble sort is stable, which means that it preserves the relative order of equal elements.

Disadvantages:

• Bubble sort is inefficient, as it performs many unnecessary comparisons and swaps.

• Bubble sort has a high time complexity, which makes it slow for large arrays.

• Bubble sort is not adaptive, which means that it does not take advantage of the existing order in the array.

How to implement Bubble Sort in Java?

Now that you know what bubble sort is and how it works, let's see how to implement it in Java. There are two versions of bubble sort that you can use: the basic algorithm and the optimized algorithm.

The basic algorithm

The basic algorithm of bubble sort is the one that we have described above. It consists of two nested loops: an outer loop that runs for n-1 iterations, and an inner loop that compares and swaps each pair of adjacent elements until the end of the unsorted part of the array. The pseudocode of the basic algorithm is as follows:

for i from 0 to n-2 for j from 0 to n-i-2 if arr[j] > arr[j+1] swap arr[j] and arr[j+1] end if end for end for

The optimized algorithm

The optimized algorithm of bubble sort is a slight modification of the basic algorithm that improves its performance. It introduces a flag variable that keeps track of whether any swap occurred in the inner loop. If no swap occurred, it means that the array is already sorted and there is no need to continue the outer loop. The pseudocode of the optimized algorithm is as follows:

flag = true for i from 0 to n-2 if flag == false break end if flag = false for j from 0 to n-i-2 if arr[j] > arr[j+1] swap arr[j] and arr[j+1] flag = true end if end for end for

The Java code example

Here is an example of how to implement both versions of bubble sort in Java. We use a helper method called swap to exchange the values of two elements in an array. We also use a helper method called printArray to display the contents of an array.

// A helper method to swap two elements in an array public static void swap(int[] arr, int i, int j) int temp = arr[i]; arr[j] = temp; // A helper method to print an array public static void printArray(int[] arr) for (int num : arr) System.out.print(num + " "); System.out.println(); // The basic bubble sort algorithm public static void bubbleSortBasic(int[] arr) int n = arr.length; for (int i = 0; i arr[j + 1]) swap(arr, j, j + 1); // The optimized bubble sort algorithm public static void bubbleSortOptimized(int[] arr) int n = arr.length; boolean flag = true; for (int i = 0; i arr[j + 1]) swap(arr, j, j + 1); flag = true; // A test case public static void main(String[] args) int[] arr = 4, 2, 1, 6, 3, 5; System.out.println("The original array is:"); printArray(arr); System.out.println("The sorted array using basic bubble sort is:"); bubbleSortBasic(arr); printArray(arr); System.out.println("The sorted array using optimized bubble sort is:"); bubbleSortOptimized(arr); printArray(arr);

How to test and analyze Bubble Sort in Java?

After implementing bubble sort in Java, you might want to test and analyze its performance and behavior. Here are some aspects that you can consider:

The test case

To test your bubble sort implementation, you can use different types of arrays as input, such as:

• An empty array

• An array with one element

• An array with two elements

• An array that is already sorted

• An array that is sorted in reverse order

• An array that has duplicate elements

• An array that has random elements

For each type of array, you can check if the output is correct and matches the expected result. You can also pri