代码重构与最佳实践：Java代码优化实例

原创迈不过友情╰ 2024-11-13 23:48 18阅读 0赞

代码重构是改善现有代码结构的过程，以提高其可读性、可维护性和性能，同时不改变其外部行为。以下是一些Java代码优化的最佳实践实例：

###1.避免不必要的对象创建**优化前：**
```javaString result = "";
for (int i =0; i <100; i++) {
 result += i;
}
```**优化后：**
```javaStringBuilder result = new StringBuilder();
for (int i =0; i <100; i++) {
 result.append(i);
}
```###2. 使用合适的数据结构**优化前：**
```javaList<Integer> numbers = new ArrayList<>();
for (int i =0; i <1000; i++) {
 numbers.add(i);
}
```**优化后：**
```javaList<Integer> numbers = new ArrayList<>(Collections.nCopies(1000,0));
for (int i =0; i <1000; i++) {
 numbers.set(i, i);
}
```###3.减少不必要的方法调用**优化前：**
```javapublic String getUserName() {
 return this.user.getName();
}
```**优化后：**
```javapublic String getUserName() {
 return user.getName();
}
```###4.利用局部变量**优化前：**
```javapublic int calculateSum(int[] numbers) {
int sum =0;
 for (int number : numbers) {
sum += number;
 }
 return sum;
}
```**优化后：**
```javapublic int calculateSum(int[] numbers) {
int sum =0;
 for (int number : numbers) {
sum += number;
 }
 return sum;
}
```
（注：这个例子中，优化前后代码相同，因为局部变量的使用已经是最佳实践。）

###5.避免使用过时的API**优化前：**
```javaString result = new String("Hello, World!");
```**优化后：**
```javaString result = "Hello, World!";
```###6. 使用并行流进行并行处理**优化前：**
```javaList<Integer> results = new ArrayList<>();
for (int i =0; i < numbers.size(); i++) {
 results.add(numbers.get(i) *2);
}
```**优化后：**
```javaList<Integer> results = numbers.parallelStream()
.map(i -> i *2)
.collect(Collectors.toList());
```###7.避免使用魔法数字**优化前：**
```javaif (age <18) {
 System.out.println("You are too young.");
}
```**优化后：**
```javapublic static final int MIN_LEGAL_AGE =18;

if (age < MIN_LEGAL_AGE) {
 System.out.println("You are too young.");
}
```###8.单一职责原则**优化前：**
```javapublic class User {
 private String name;
 private int age;

public void printUserInfo() {
 System.out.println("Name: " + name + ", Age: " + age);
 }

public void saveUser() {
// Save user to database }
}
```**优化后：**
```javapublic class User {
 private String name;
 private int age;

public void printUserInfo() {
 System.out.println("Name: " + name + ", Age: " + age);
 }
}

public class UserDAO {
 public void saveUser(User user) {
// Save user to database }
}
```这些只是一些基本的代码优化实例。在实际开发中，代码优化应根据具体情况和需求进行。记得在重构代码时，始终保持代码的可读性和可维护性。