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Java Best Practices

This guide covers essential Java programming best practices for writing clean, efficient, and maintainable code.

🎯 Core Java Best Practices

Naming Conventions

  • Classes: Use PascalCase (e.g., StudentRecord, DatabaseManager)
  • Methods: Use camelCase (e.g., calculateTotal(), getUserInput())
  • Variables: Use camelCase with meaningful names (e.g., studentName, totalAmount)
  • Constants: Use UPPER_SNAKE_CASE (e.g., MAX_RETRY_ATTEMPTS, DEFAULT_TIMEOUT)
  • Packages: Use lowercase with dots (e.g., com.example.utils)

Code Organization

  • Single Responsibility: Each class should have one reason to change
  • DRY Principle: Don't Repeat Yourself - extract common code into methods
  • Encapsulation: Keep fields private, use getters/setters
  • Interface Segregation: Prefer small, focused interfaces

Memory Management

  • Object Creation: Minimize object creation in loops
  • String Handling: Use StringBuilder for string concatenation in loops
  • Collections: Choose appropriate collection types (ArrayList vs. LinkedList)
  • Resource Management: Use try-with-resources for AutoCloseable objects

Exception Handling

  • Specific Exceptions: Catch specific exceptions, not generic Exception
  • Custom Exceptions: Create meaningful custom exception classes
  • Finally Blocks: Always clean up resources in finally blocks
  • Logging: Log exceptions with context information

🔧 Java-Specific Techniques

Input/Output

// Good: Using try-with-resources
try (Scanner scanner = new Scanner(System.in)) {
    int number = scanner.nextInt();
    System.out.println("You entered: " + number);
} catch (InputMismatchException e) {
    System.err.println("Invalid input: Please enter a number");
}

// Bad: Manual resource management
Scanner scanner = new Scanner(System.in);
int number = scanner.nextInt();
scanner.close(); // Might not execute if exception occurs

Collection Usage

// Good: Use diamond operator for type inference
List<String> names = new ArrayList<>();

// Good: Use enhanced for-loop
for (String name : names) {
    System.out.println(name);
}

// Bad: Raw types and traditional for-loop
List names = new ArrayList();
for (int i = 0; i < names.size(); i++) {
    System.out.println(names.get(i));
}

Method Design

// Good: Clear parameters and return type
public double calculateAverage(List<Integer> numbers) {
    if (numbers == null || numbers.isEmpty()) {
        throw new IllegalArgumentException("Numbers list cannot be null or empty");
    }

    double sum = 0;
    for (int num : numbers) {
        sum += num;
    }
    return sum / numbers.size();
}

// Bad: Unclear method purpose
public Object process(List data) {
    // What does this method do?
    return null;
}

⚠️ Common Java Pitfalls

Null Pointer Exceptions

  • Always check for null before method calls
  • Use Optional for potentially null values
  • Use Objects.equals() for null-safe comparison

String Comparison

// Wrong: Reference comparison
if (name == "John") { ... }

// Correct: Value comparison
if (name.equals("John")) { ... }

// Better: Null-safe comparison
if ("John".equals(name)) { ... }

Floating Point Arithmetic

// Bad: Direct comparison
if (0.1 + 0.2 == 0.3) { ... } // false!

// Good: Use epsilon comparison
private static final double EPSILON = 0.000001;
if (Math.abs((0.1 + 0.2) - 0.3) < EPSILON) { ... }

🚀 Performance Optimization

Loop Optimization

// Good: Cache array length
int[] array = getLargeArray();
int length = array.length;
for (int i = 0; i < length; i++) {
    // Process array[i]
}

// Bad: Repeated length calculation
for (int i = 0; i < array.length; i++) {
    // Process array[i]
}

StringBuilder Usage

// Good: StringBuilder for concatenation
StringBuilder result = new StringBuilder();
for (int i = 0; i < 1000; i++) {
    result.append(i).append(" ");
}

// Bad: String concatenation in loop
String result = "";
for (int i = 0; i < 1000; i++) {
    result += i + " ";
}