Java Best Practices for Clean Code

 Writing clean, maintainable Java code is essential for building reliable software. Here are some Java best practices for clean code, categorized for clarity:

✅ 1. Naming Conventions

Use meaningful and descriptive names

java

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// Bad

int d;  

// Good

int daysSinceLastUpdate;

Use camelCase for variables and methods, PascalCase for classes

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int maxCount;

void processData();

class UserProfile { }

Avoid abbreviations unless they are well-known

Use maximumValue instead of maxVal, unless it’s a domain standard.

✅ 2. Code Structure and Formatting

Stick to consistent indentation (4 spaces is typical)

Group related methods together

Limit class size: One class per file, ideally under ~300 lines

✅ 3. Object-Oriented Principles

Follow the SOLID principles:

Single Responsibility

Open/Closed

Liskov Substitution

Interface Segregation

Dependency Inversion

Use encapsulation: keep fields private, expose via getters/setters

Prefer composition over inheritance when possible

✅ 4. Error Handling

Use exceptions wisely

Avoid empty catch blocks

Catch specific exceptions, not general ones

Don't use exceptions for control flow

✅ 5. Comments and Documentation

Write self-explanatory code to minimize need for comments

Use Javadoc for public APIs

Avoid redundant comments

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// Bad

int age; // age of the person

// Good

/**

 * Age in years.

 */

private int age;

✅ 6. Code Reusability and DRY Principle

Avoid repetition: extract methods for repeated logic

Use utility/helper classes for shared functionality

✅ 7. Collections and Streams

Prefer interfaces (List, Map) over implementations (ArrayList)

Use Java Streams for clean, functional-style operations

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List<String> names = people.stream()

                           .filter(p -> p.getAge() > 18)

                           .map(Person::getName)

                           .collect(Collectors.toList());

✅ 8. Immutability and Final

Use final for constants and variables that shouldn’t change

Prefer immutable classes for data transfer

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public final class User {

    private final String name;

    private final int age;

    // constructor, getters, no setters

}

✅ 9. Logging

Use logging frameworks like SLF4J or Log4J2 instead of System.out.println

Log at appropriate levels: INFO, DEBUG, ERROR, etc.

✅ 10. Unit Testing

Write unit tests using JUnit/TestNG

Follow TDD principles when possible

Use mocking frameworks like Mockito

Cover edge cases and boundary conditions

✅ 11. Dependency Management

Use build tools like Maven or Gradle

Define dependencies in pom.xml or build.gradle

Avoid hardcoding paths, versions, or credentials

✅ 12. Avoid Anti-Patterns

Don’t use magic numbers: use constants

Avoid God classes: break into smaller, focused classes

Don’t overuse static methods/variables

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