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Lära Understanding SOLID Principles | Fundamental Coding Principles
Concepts and Principles in Java

bookUnderstanding SOLID Principles

When you write Java code, following strong design principles helps you create software that is easy to understand, maintain, and extend. The SOLID principles are a set of five fundamental guidelines for object-oriented programming that make your code more robust and flexible. These principles are:

Single Responsibility Principle (SRP)
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Explanation: A class should have only one reason to change, meaning it should focus on a single task or responsibility.

Implications in Java: If a class grows to handle multiple concerns, it becomes harder to maintain and test. For example, mixing data persistence logic with business logic in the same class violates SRP.

Common Pitfalls: Creating "God classes" that handle too many unrelated tasks, making the codebase fragile and hard to update.

Open/Closed Principle (OCP)
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Explanation: Software entities like classes, modules, and functions should be open for extension but closed for modification.

Implications in Java: You should be able to add new features by extending existing classes or implementing interfaces, rather than altering existing code. This is often achieved using inheritance or the strategy pattern.

Common Pitfalls: Modifying existing classes every time requirements change, leading to bugs and regression issues.

Liskov Substitution Principle (LSP)
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Explanation: Objects of a superclass should be replaceable with objects of a subclass without affecting the correctness of the program.

Implications in Java: Subclasses must honor the contracts of their superclasses. For example, overriding methods should not throw unexpected exceptions or change expected behaviors.

Common Pitfalls: Subclasses that override parent behavior in incompatible ways, causing runtime errors or logic bugs.

Interface Segregation Principle (ISP)
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Explanation: No client should be forced to depend on methods it does not use; interfaces should be specific and focused.

Implications in Java: Instead of having large interfaces with many methods, break them into smaller, role-specific interfaces. This lets classes implement only what they need.

Common Pitfalls: Creating "fat" interfaces that force implementing classes to provide empty or meaningless method bodies.

Dependency Inversion Principle (DIP)
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Explanation: High-level modules should not depend on low-level modules; both should depend on abstractions.

Implications in Java: Use interfaces or abstract classes so that concrete implementations can be swapped easily, supporting testability and flexibility.

Common Pitfalls: Directly instantiating dependencies inside classes, which makes code harder to test and modify.

Understanding and applying these principles in Java will help you avoid common pitfalls such as tightly coupled code, code duplication, and classes that are difficult to test or extend in the future.

question mark

Which of the following best describes the SOLID principles in Java?

Select the correct answer

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Hur kan vi förbättra det?

Tack för dina kommentarer!

Avsnitt 1. Kapitel 1

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bookUnderstanding SOLID Principles

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When you write Java code, following strong design principles helps you create software that is easy to understand, maintain, and extend. The SOLID principles are a set of five fundamental guidelines for object-oriented programming that make your code more robust and flexible. These principles are:

Single Responsibility Principle (SRP)
expand arrow

Explanation: A class should have only one reason to change, meaning it should focus on a single task or responsibility.

Implications in Java: If a class grows to handle multiple concerns, it becomes harder to maintain and test. For example, mixing data persistence logic with business logic in the same class violates SRP.

Common Pitfalls: Creating "God classes" that handle too many unrelated tasks, making the codebase fragile and hard to update.

Open/Closed Principle (OCP)
expand arrow

Explanation: Software entities like classes, modules, and functions should be open for extension but closed for modification.

Implications in Java: You should be able to add new features by extending existing classes or implementing interfaces, rather than altering existing code. This is often achieved using inheritance or the strategy pattern.

Common Pitfalls: Modifying existing classes every time requirements change, leading to bugs and regression issues.

Liskov Substitution Principle (LSP)
expand arrow

Explanation: Objects of a superclass should be replaceable with objects of a subclass without affecting the correctness of the program.

Implications in Java: Subclasses must honor the contracts of their superclasses. For example, overriding methods should not throw unexpected exceptions or change expected behaviors.

Common Pitfalls: Subclasses that override parent behavior in incompatible ways, causing runtime errors or logic bugs.

Interface Segregation Principle (ISP)
expand arrow

Explanation: No client should be forced to depend on methods it does not use; interfaces should be specific and focused.

Implications in Java: Instead of having large interfaces with many methods, break them into smaller, role-specific interfaces. This lets classes implement only what they need.

Common Pitfalls: Creating "fat" interfaces that force implementing classes to provide empty or meaningless method bodies.

Dependency Inversion Principle (DIP)
expand arrow

Explanation: High-level modules should not depend on low-level modules; both should depend on abstractions.

Implications in Java: Use interfaces or abstract classes so that concrete implementations can be swapped easily, supporting testability and flexibility.

Common Pitfalls: Directly instantiating dependencies inside classes, which makes code harder to test and modify.

Understanding and applying these principles in Java will help you avoid common pitfalls such as tightly coupled code, code duplication, and classes that are difficult to test or extend in the future.

question mark

Which of the following best describes the SOLID principles in Java?

Select the correct answer

Var allt tydligt?

Hur kan vi förbättra det?

Tack för dina kommentarer!

Avsnitt 1. Kapitel 1
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