الواجهات و Lambda

public interface Drawable {
    void draw();  // دالة مجردة
    void setColor(String color);  // دالة مجردة
}

public class Circle implements Drawable {
    private String color;
    
    @Override
    public void draw() {
        System.out.println("رسم دائرة");
    }
    
    @Override
    public void setColor(String color) {
        this.color = color;
        System.out.println("اللون: " + color);
    }
}

public class Rectangle implements Drawable {
    private String color;
    
    @Override
    public void draw() {
        System.out.println("رسم مستطيل");
    }
    
    @Override
    public void setColor(String color) {
        this.color = color;
        System.out.println("اللون: " + color);
    }
}

Drawable[] shapes = {new Circle(), new Rectangle()};

for (Drawable shape : shapes) {
    shape.setColor("أحمر");
    shape.draw();
}

public interface Printable {
    void print();
}

public interface Serializable {
    void save();
}

public class Document implements Printable, Serializable {
    @Override
    public void print() {
        System.out.println("طباعة المستند");
    }
    
    @Override
    public void save() {
        System.out.println("حفظ المستند");
    }
}

public interface Logger {
    void log(String message);
    
    // دالة افتراضية
    default void logError(String message) {
        log("خطأ: " + message);
    }
    
    // دالة ثابتة
    static Logger createConsoleLogger() {
        return message -> System.out.println("[LOG] " + message);
    }
}

public class FileLogger implements Logger {
    @Override
    public void log(String message) {
        System.out.println("[FILE] " + message);
    }
}

// الاستخدام
Logger logger = new FileLogger();
logger.log("رسالة");           // [FILE] رسالة
logger.logError("خطأ");       // [FILE] خطأ: خطأ

Logger console = Logger.createConsoleLogger();
console.log("رسالة");         // [LOG] رسالة

@FunctionalInterface
public interface Calculator {
    int calculate(int a, int b);
}

// استخدام Lambda
Calculator add = (a, b) -> a + b;
Calculator subtract = (a, b) -> a - b;
Calculator multiply = (a, b) -> a * b;

System.out.println(add.calculate(5, 3));       // 8
System.out.println(subtract.calculate(5, 3));  // 2
System.out.println(multiply.calculate(5, 3));  // 15

public class Student implements Comparable<Student> {
    private String name;
    private double gpa;
    
    public Student(String name, double gpa) {
        this.name = name;
        this.gpa = gpa;
    }
    
    @Override
    public int compareTo(Student other) {
        return Double.compare(this.gpa, other.gpa);
    }
}

// استخدام
ArrayList<Student> students = new ArrayList<>();
students.add(new Student("أحمد", 3.5));
students.add(new Student("محمد", 3.8));
students.add(new Student("علي", 3.2));

Collections.sort(students);  // ترتيب حسب GPA

public class MyTask implements Runnable {
    @Override
    public void run() {
        System.out.println("المهمة تعمل في خيط: " + Thread.currentThread().getName());
    }
}

// استخدام
Thread thread = new Thread(new MyTask());
thread.start();

// بـ Lambda
Thread thread2 = new Thread(() -> {
    System.out.println("Lambda تعمل في خيط");
});
thread2.start();