遵循命名規(guī)范使代碼像散文一樣易讀；2. 方法要小而專注，單一職責(zé)便于測試和復(fù)用；3. 寫有意義的注釋解釋“為什么”，而非顯而易見的操作；4. 優(yōu)先使用不可變性和封裝，防止外部意外修改；5. 異常要妥善處理，不忽略并提供清晰信息；6. 單元測試需命名清晰、覆蓋關(guān)鍵路徑；7. 合理使用現(xiàn)代Java特性如var和Stream提升可讀性；8. 按功能分層組織包結(jié)構(gòu)，提升項目導(dǎo)航效率——這些實踐共同確保Java代碼長期可維護。

Writing maintainable Java code isn’t just about making it work—it’s about making it easy to understand, modify, and extend over time. Whether you're working solo or in a team, clean and maintainable code saves hours of debugging, onboarding, and refactoring. Here are key best practices that experienced Java developers follow:

? 1. Follow Consistent Naming Conventions

Use clear, descriptive names for classes, methods, variables, and constants.

• Classes: PascalCase → UserService, OrderProcessor
• Methods: camelCase → calculateTotal(), isValidUser()
• Variables: camelCase → userName, orderCount
• Constants: UPPER_SNAKE_CASE → MAX_RETRIES, DEFAULT_TIMEOUT_MS

Why it matters: Code should read like prose. If someone can guess what a method does from its name, you’re on the right track.

? 2. Keep Methods Small and Focused (Single Responsibility)

Each method should do one thing—and do it well.
Aim for methods under 20–30 lines. If it’s longer, consider extracting parts into smaller methods.

Example:

public void processOrder(Order order) {
    validateOrder(order);
    calculateTotal(order);
    saveToDatabase(order);
}

This is easier to test, debug, and reuse than a 100-line monolith.

? 3. Write Meaningful Comments—Not Obvious Ones

Avoid:

i++; // increment i

Instead, explain why something is done:

// Retry up to 3 times due to known flakiness in payment gateway
for (int i = 0; i < MAX_RETRIES; i++) {
    ...
}

Also use Javadoc for public APIs:

/**
 * Calculates total price including tax and shipping.
 * @param items List of order items
 * @return total amount in USD
 */
public BigDecimal calculateTotal(List<Item> items) { ... }

? 4. Favor Immutability and Encapsulation

• Make fields private unless there's a strong reason not to.
• Return copies of mutable objects (like List, Date) from getters to prevent external modification.
• Use final for variables that shouldn’t change after assignment.

Example:

public class User {
    private final String name;
    private List<String> roles;

    public User(String name, List<String> roles) {
        this.name = name;
        this.roles = new ArrayList<>(roles); // defensive copy
    }

    public List<String> getRoles() {
        return new ArrayList<>(roles); // prevent external mutation
    }
}

? 5. Handle Exceptions Gracefully

• Don’t catch and ignore exceptions (catch (Exception e) {}).
• Log meaningful errors or wrap them in custom exceptions when needed.
• Fail fast: validate inputs early and throw descriptive exceptions.

Good example:

if (userId == null) {
    throw new IllegalArgumentException("User ID cannot be null");
}

? 6. Write Unit Tests (and Keep Them Clean Too)

• Test one behavior per test method.
• Use clear naming: shouldThrowExceptionWhenUserIdIsNull()
• Use tools like JUnit 5 + Mockito for mocks.
• Aim for high coverage, but prioritize testing critical paths over vanity metrics.

? 7. Use Modern Java Features Wisely

• Prefer var for local variables when type is obvious:

  var users = new ArrayList<User>();

• Use Streams for filtering, mapping, etc.—but don’t overcomplicate:

  List<String> names = users.stream()
                            .map(User::getName)
                            .toList();

• Avoid premature optimization—readability > cleverness.

? 8. Organize Code with Packages and Layers

Structure your project logically:

com.yourapp
├── service      → Business logic
├── repository   → Data access
├── controller   → REST endpoints (if web app)
├── model        → DTOs, entities
└── config       → Spring or other configs

This makes navigation intuitive—even for new developers.

Bottom line: Maintainable Java code is readable, testable, and predictable. It respects conventions, avoids magic, and assumes the next reader knows nothing about your intent. Write code like you’re explaining it to your future self—or a junior dev inheriting your project.

Basically, if someone can read your code and say “oh, I get it” without asking you—mission accomplished.

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