滚雪球学Java(29)：数组长度和排序算法：让你的程序更高效，有两下子！

Array Length and Sorting Algorithms in Java

This article, part of the 'Rolling Snowball Learning Java' column, delves into the concept of array lengths and the use of sorting algorithms to enhance program efficiency in Java. After understanding the basics of arrays, we explore advanced applications such as managing array lengths and implementing sorting algorithms. These concepts help to optimize data handling and program performance.

Summary

The article discusses the concept of array length in Java and introduces common sorting algorithms including bubble sort, selection sort, and quicksort. It provides examples to demonstrate how to implement these algorithms and discusses their efficiency and applicable scenarios.

• Array length represents the number of elements in an array, accessible via the length property.
• Sorting algorithms are used to order arrays in ascending or descending sequence.
• Common sorting algorithms include bubble sort, selection sort, and quicksort.
• The efficiency of sorting algorithms depends on the scale of data and algorithm implementation.

Java Arrays

Array Length

Array length is a key attribute determining array capacity. In Java, an array's length is immutable once created. To adjust the size, one must create a new array and copy the elements. Understanding the concept of array length is vital for array management and memory usage. For example, the length of an array can be obtained as follows:

        
int[] arr = {1, 2, 3, 4, 5};
int length = arr.length; // 5
        
    

Note that the array length is fixed, and to add or remove elements, a new array must be created.

Sorting Algorithms

Sorting is a classic problem in computer science involving rearranging a set of data in a specific order. Java provides various sorting algorithms, each with its characteristics and suitable scenarios. Sorting algorithms are applied to arrange data in ascending or descending order. Popular sorting algorithms in Java are bubble sort, selection sort, and quicksort.

Bubble Sort

Bubble sort is a straightforward sorting method that iterates through the array, compares the size of adjacent elements, and swaps their positions if necessary. Its basic idea is to compare adjacent elements and swap them if the preceding one is larger, continuing this process until the entire array is sorted. Below is an example implementation of bubble sort:

        
public static void bubbleSort(int[] arr) {
    int n = arr.length;
    for (int i = 0; i < n-1; i++) {
        // Implementation details...
    }
}