In-depth analysis of Java bubble sort algorithm and common implementation methods

Detailed explanation of Java bubble sorting algorithm and common implementation methods

Introduction:
Bubble sorting is a basic sorting algorithm, which uses Sorting by comparison and exchange. Although the time complexity of bubble sort is high (O(n^2)), due to its simple implementation, it is the basis for understanding the sorting algorithm and is also one of the common questions in interviews. This article will introduce in detail the principles, steps and common implementation methods of the Java bubble sort algorithm, and also give code examples.

1. Principle and steps:
The basic idea of ​​bubble sorting is to compare the elements to be sorted from beginning to end. If the adjacent elements are in reverse order, exchange them until the entire sequence is in order. The specific steps are as follows:

1. Start from the first element of the sequence to be sorted and compare the two adjacent elements.
2. If the first element is larger than the second element, swap their positions.
3. Continue to compare the second element and the third element, and exchange them if they are in reverse order, otherwise they remain unchanged.
4. Repeat the above steps until the entire sequence is in order.

2. Common implementation methods in Java:

1. Ordinary bubble sort:
   Ordinary bubble sort is to traverse the entire sequence to be sorted and sort each adjacent element Compare and swap. The specific implementation code is as follows:

public static void bubbleSort(int[] arr) {
    int n = arr.length;
    for (int i = 0; i < n - 1; i++) {
        for (int j = 0; j < n - i - 1; j++) {
            if (arr[j] > arr[j + 1]) {
                // 交换相邻元素的位置
                int temp = arr[j];
                arr[j] = arr[j + 1];
                arr[j + 1] = temp;
            }
        }
    }
}

2. Optimized bubble sorting:
   In ordinary bubble sorting, each sorting pass must traverse the entire sequence to be sorted, including the already ordered sequence. part. In fact, if no exchange is performed in a certain sorting pass, it means that the entire sequence is in order and the loop can be exited directly. This can reduce unnecessary comparison and exchange operations and improve sorting efficiency. The specific implementation code is as follows:

public static void bubbleSortOptimized(int[] arr) {
    int n = arr.length;
    boolean swapped; // 标识是否有交换操作
    for (int i = 0; i < n - 1; i++) {
        swapped = false;
        for (int j = 0; j < n - i - 1; j++) {
            if (arr[j] > arr[j + 1]) {
                // 交换相邻元素的位置
                int temp = arr[j];
                arr[j] = arr[j + 1];
                arr[j + 1] = temp;
                swapped = true;
            }
        }
        // 如果没有进行任何交换，说明已经有序，直接退出循环
        if (!swapped) {
            break;
        }
    }
}

3. Examples and testing:
An example is given below to test and verify the correctness of the code:

public static void main(String[] args) {
    int[] arr = {64, 34, 25, 12, 22, 11, 90};
    
    System.out.println("排序前：");
    for (int num : arr) {
        System.out.print(num + " ");
    }
    
    bubbleSortOptimized(arr);
    
    System.out.println("
排序后：");
    for (int num : arr) {
        System.out.print(num + " ");
    }
}

The output result is:
Before sorting: 64 34 25 12 22 11 90
After sorting: 11 12 22 25 34 64 90

Conclusion:
Bubble sorting is a simple but less efficient sorting algorithm , which implements sorting through comparison and exchange between adjacent elements. This article introduces the principles, steps and common implementation methods of the Java bubble sort algorithm in detail, and gives code examples for testing and verification. In practical applications, we can choose ordinary bubble sort or optimized bubble sort according to specific circumstances to improve sorting efficiency.

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