import jakarta.ejb.Stateless;

@Stateless
public class CalculatorBean {
    
    public int add(int a, int b) {
        return a + b;
    }
}

#کاربرـحرفهـای

🆔 @javapro_ir
🆔 @group_javapro

import jakarta.persistence.*;

@Entity
public class User {
    
    @Id
    @GeneratedValue
    private Long id;

    private String name;

    private String email;

    // Getter و Setterها
}

import jakarta.ejb.Stateless;
import jakarta.persistence.*;

@Stateless
public class UserService {

    @PersistenceContext
    private EntityManager em;

    public void addUser(String name, String email) {
        User user = new User();
        user.setName(name);
        user.setEmail(email);
        em.persist(user); // ذخیره در پایگاه‌داده
    }

    public User findUser(Long id) {
        return em.find(User.class, id); // بازیابی کاربر بر اساس ID
    }
}

#کاربرـحرفهـای

🆔 @javapro_ir
🆔 @group_javapro

<dependency>
    <groupId>org.apache.commons</groupId>
    <artifactId>commons-exec</artifactId>
    <version>1.3</version>
</dependency>

import org.apache.commons.exec.*;

public class ShellCommandExample {
    public static void main(String[] args) {
        try {
            CommandLine cmd = new CommandLine("mkdir");
            cmd.addArgument("-p");
            cmd.addArgument("/tmp/myfolder");

            DefaultExecutor executor = new DefaultExecutor();
            int exitCode = executor.execute(cmd);

            System.out.println("کد خروج: " + exitCode);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

import org.apache.commons.exec.*;

import java.io.ByteArrayOutputStream;

public class ShellListDirectory {
    public static void main(String[] args) {
        try {
            CommandLine cmd = CommandLine.parse("ls -la /tmp");

            ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
            PumpStreamHandler streamHandler = new PumpStreamHandler(outputStream);

            DefaultExecutor executor = new DefaultExecutor();
            executor.setStreamHandler(streamHandler);

            executor.execute(cmd);

            String output = outputStream.toString("UTF-8");
            System.out.println("خروجی دستور:\n" + output);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

#کاربرـپیشرفته

🆔 @javapro_ir
🆔 @group_javapro

import java.nio.file.*;
import java.io.IOException;
import java.util.List;

public class ReadFileExample {
    public static void main(String[] args) {
        try {
            Path filePath = Paths.get("data.txt");
            List<String> lines = Files.readAllLines(filePath);

            for (String line : lines) {
                System.out.println(line);
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

import java.nio.file.*;
import java.io.IOException;
import java.util.Arrays;

public class WriteFileExample {
    public static void main(String[] args) {
        try {
            Path filePath = Paths.get("output.txt");
            Files.write(filePath, Arrays.asList("Hello World", "This is a text file"), StandardOpenOption.CREATE);
            System.out.println("File written successfully.");
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

Files.write(filePath, Arrays.asList("New line added"), StandardOpenOption.CREATE, StandardOpenOption.APPEND);

#کاربرـپیشرفته

🆔 @javapro_ir
🆔 @group_javapro

String s = "hello";
s += " world";

String result = "";
for (int i = 0; i < 10000; i++) {
    result += i;
}

StringBuilder result = new StringBuilder();
for (int i = 0; i < 10000; i++) {
    result.append(i);
}

#کاربر_مبتدی

🆔 @javapro_ir
🆔 @group_javapro

String a = "hello";
String b = "hello";
String c = new String("hello");

System.out.println(a == b);     // true (به علت String Pool)
System.out.println(a == c);     // false (شیء جدید در Heap)
System.out.println(a.equals(c)); // true (برابری محتوا)

class User {
    String name;
    User(String name) {
        this.name = name;
    }
}

public class Test {
    public static void main(String[] args) {
        User u1 = new User("Ali");
        User u2 = new User("Ali");

        System.out.println(u1 == u2);        // false
        System.out.println(u1.equals(u2));   // false (تا زمانی که equals بازنویسی نشده باشد)
    }
}

@Override
public boolean equals(Object obj) {
    if (this == obj) return true;
    if (obj == null || getClass() != obj.getClass()) return false;
    User user = (User) obj;
    return name.equals(user.name);
}

#کاربر_مبتدی

🆔 @javapro_ir
🆔 @group_javapro

public class Counter {
    int count = 0;
}

public class Counter {
    static int count = 0;
}

public class Example {
    int instanceVar = 0;
    static int staticVar = 0;

    public void increment() {
        instanceVar++;
        staticVar++;
    }
}

public class Main {
    public static void main(String[] args) {
        Example a = new Example();
        Example b = new Example();

        a.increment();
        b.increment();

        System.out.println("a.instanceVar = " + a.instanceVar); // 1
        System.out.println("b.instanceVar = " + b.instanceVar); // 1

        System.out.println("a.staticVar = " + a.staticVar);     // 2
        System.out.println("b.staticVar = " + b.staticVar);     // 2
    }
}

Counter.count++;
System.out.println(Counter.count);

#کاربر_مبتدی

🆔 @javapro_ir
🆔 @group_javapro

public class Calculator {
    public int add(int a, int b) {
        return a + b;
    }

    public double add(double a, double b) {
        return a + b;
    }
}

class Animal {
    public void speak() {
        System.out.println("Animal speaks");
    }
}

class Dog extends Animal {
    @Override
    public void speak() {
        System.out.println("Dog barks");
    }
}

public class Test {
    public static void main(String[] args) {
        Animal animal = new Dog();
        animal.speak();  // خروجی: Dog barks
    }
}

#کاربرـپیشرفته

🆔 @javapro_ir
🆔 @group_javapro