Interface Segregation Principle (ISP)

1. Introduction

The Interface Segregation Principle is one of the five SOLID principles of object-oriented programming and design. It states that no client should be forced to depend on methods it does not use. This principle encourages the creation of smaller, more focused interfaces instead of large, general-purpose ones.

2. Key Concepts

3. Best Practices

• Design interfaces to be client-specific.
• Use multiple interfaces for different client needs.
• Avoid "fat" interfaces that include unnecessary methods.
• Refactor large interfaces into smaller ones as needed.

4. Code Example

interface Printer {
    void print(Document doc);
}

interface Scanner {
    void scan(Document doc);
}

class MultiFunctionPrinter implements Printer, Scanner {
    public void print(Document doc) {
        // Print implementation
    }
    public void scan(Document doc) {
        // Scan implementation
    }
}

class SimplePrinter implements Printer {
    public void print(Document doc) {
        // Print implementation
    }
}

    

In this example, we have separated the functionalities into two interfaces: Printer and Scanner. The MultiFunctionPrinter implements both, while the SimplePrinter only implements the Printer interface, adhering to the ISP.

5. FAQ