The Core Logic (Step-by-Step)

At its heart, the Bubble Sort algorithm is one of the most straightforward sorting methods. Its logic is built on a simple, repetitive action: comparing two adjacent elements and swapping them if they are not in the correct order. Let's break down this process into clear, manageable steps to understand how Bubble Sort works from the ground up. 

The algorithm always starts its journey at the very first element of the array. It takes the first two elements (at index 0 and index 1) and compares them.

• If the first element is greater than the second, it means they are in the wrong order. So, the algorithm swaps them.
• If the first element is smaller than or equal to the second, they are already in the correct order, so no action is needed.

This adjacent element comparison is the fundamental operation of Bubble Sort.

Complete One Full Pass

After the first comparison, the algorithm moves one position to the right. It now compares the elements at index 1 and index 2 and performs a swap if necessary. It continues this process, ompare, and swap if needed for every adjacent pair until it reaches the end of the array.

When the algorithm completes this journey from the start to the end of the array, we call it one full pass. A crucial thing happens after the first pass: the largest element in the entire array is guaranteed to have "bubbled up" to its correct final position at the very end of the array.

Repeat for Remaining Elements

Now that the largest element is sorted and in its final place, we don't need to check it again. For the second pass, the algorithm repeats the exact same process, but this time it only needs to go up to the second-to-last element. After the second pass, the second-largest element will be in its correct position.

This pattern continues. With each new pass, the sorted portion at the end of the array grows by one, and the next pass has one less element to check. This step-by-step sorting approach ensures that the list becomes progressively more ordered.

Stop When Sorted

How does the algorithm know when to stop? It will continue making passes through the array as long as swaps are being made. If it completes a full pass without making a single swap, it means every element is in its correct sorted order. At that point, the array is fully sorted, and the algorithm can terminate. This is a key optimization that prevents unnecessary checks on an already sorted list, making the sorting in Java more efficient in the best-case scenario.