public void printNumbers(int... numbers) {
    for (int num : numbers) {
        System.out.print(num + " ");
    }
}

printNumbers(1, 2, 3);
printNumbers(10, 20, 30, 40, 50);
printNumbers(); // حتی بدون هیچ آرگومانی

public void example(String name, int... scores) { }

public class VarargsExample {
    public static int sum(int... numbers) {
        int total = 0;
        for (int num : numbers) {
            total += num;
        }
        return total;
    }

    public static void main(String[] args) {
        System.out.println(sum(1, 2, 3));        // خروجی: 6
        System.out.println(sum(10, 20));         // خروجی: 30
        System.out.println(sum());               // خروجی: 0
    }
}

#کاربرـحرفهـای

🆔 @javapro_ir
🆔 @group_javapro

public class User {
    private String name;

    public String getName() {
        return name;
    }
}

public class Test {
    public static void main(String[] args) {
        User user = null;
        // اینجا خطای NullPointerException رخ می‌دهد
        System.out.println(user.getName());
    }
}

import java.util.Optional;

public class Test {
    public static void main(String[] args) {
        Optional<String> name = Optional.ofNullable(null);

        // اگر مقدار null باشد، "Unknown" چاپ می‌شود
        System.out.println(name.orElse("Unknown"));
    }
}

Optional<String> opt1 = Optional.of("Hello");       // مقدار حتماً باید غیر null باشد
Optional<String> opt2 = Optional.ofNullable(null);  // می‌تواند null یا غیر null باشد
Optional<String> opt3 = Optional.empty();           // همیشه خالی

if(opt1.isPresent()) {
    System.out.println(opt1.get());
}

String value = opt2.orElse("Default Value");
String value2 = opt2.orElseGet(() -> "Generated Value");

opt1.ifPresent(v -> System.out.println("Value: " + v));

Optional<String> upper = opt1.map(String::toUpperCase);
System.out.println(upper.orElse("No Value"));

#کاربرـحرفهـای

🆔 @javapro_ir
🆔 @group_javapro

import java.util.function.Predicate;

public class Main {
    public static void main(String[] args) {
        Predicate<String> isLong = s -> s.length() > 5;

        System.out.println(isLong.test("Hello"));   // false
        System.out.println(isLong.test("FunctionalInterface")); // true
    }
}

import java.util.function.Function;

public class Main {
    public static void main(String[] args) {
        Function<String, Integer> stringLength = s -> s.length();

        System.out.println(stringLength.apply("Java"));       // 4
        System.out.println(stringLength.apply("LambdaExpr")); // 10
    }
}

import java.util.function.Consumer;

public class Main {
    public static void main(String[] args) {
        Consumer<String> printer = s -> System.out.println("Hello, " + s);

        printer.accept("Ali");   // Hello, Ali
        printer.accept("Sara");  // Hello, Sara
    }
}

import java.util.function.*;

public class Main {
    public static void main(String[] args) {
        Predicate<Integer> isEven = n -> n % 2 == 0;
        Function<Integer, String> toString = n -> "عدد شما: " + n;
        Consumer<String> show = s -> System.out.println(s);

        int number = 8;
        if (isEven.test(number)) {
            String result = toString.apply(number);
            show.accept(result);  // خروجی: عدد شما: 8
        }
    }
}

#کاربرـپیشرفته

🆔 @javapro_ir
🆔 @group_javapro

constructor

getters

toString(), equals(), hashCode()

public record Person(String name, int age) { }

public final class Person {
    private final String name;
    private final int age;

    public Person(String name, int age) {
        this.name = name;
        this.age = age;
    }

    public String name() { return name; }
    public int age() { return age; }

    @Override
    public String toString() { return "Person[name=" + name + ", age=" + age + "]"; }

    @Override
    public boolean equals(Object o) { ... }

    @Override
    public int hashCode() { ... }
}

public class Main {
    public static void main(String[] args) {
        Person p1 = new Person("Ali", 25);
        Person p2 = new Person("Ali", 25);

        System.out.println(p1); // Person[name=Ali, age=25]
        System.out.println(p1.equals(p2)); // true
    }
}

public record Rectangle(double width, double height) {
    public double area() {
        return width * height;
    }
}

public class Main {
    public static void main(String[] args) {
        Rectangle r = new Rectangle(5, 3);
        System.out.println("Area = " + r.area()); // Area = 15.0
    }
}

#کاربرـحرفهـای

🆔 @javapro_ir
🆔@group_javapro

import lombok.Data;

@Data
public class User {
    private String name;
    private int age;
}

public class User {
    private String name;
    private int age;

    // Getters & Setters
    public String getName() { return name; }
    public void setName(String name) { this.name = name; }
    public int getAge() { return age; }
    public void setAge(int age) { this.age = age; }

    // toString
    @Override
    public String toString() {
        return "User(name=" + name + ", age=" + age + ")";
    }

    // equals & hashCode
    @Override
    public boolean equals(Object o) { /* کد تولیدشده */ }
    @Override
    public int hashCode() { /* کد تولیدشده */ }
}

public class Main {
    public static void main(String[] args) {
        User u1 = new User();
        u1.setName("Saleh");
        u1.setAge(23);

        System.out.println(u1); 
        // خروجی: User(name=Saleh, age=23)

        User u2 = new User();
        u2.setName("Saleh");
        u2.setAge(23);

        System.out.println(u1.equals(u2)); 
        // true چون Lombok خودش equals و hashCode را نوشته
    }
}

<dependency>
  <groupId>org.projectlombok</groupId>
  <artifactId>lombok</artifactId>
  <version>1.18.30</version>
  <scope>provided</scope>
</dependency>

compileOnly 'org.projectlombok:lombok:1.18.30'
annotationProcessor 'org.projectlombok:lombok:1.18.30'

#کاربرـحرفهـای

🆔 @javapro_ir
🆔 @group_javapro