成为高级开发者，必须掌握这些Java开发的核心技术

public class MultiThreadExample {
    public static void main(String[] args) {
        Thread thread1 = new Thread(new MyThread());
        Thread thread2 = new Thread(new MyThread());
        thread1.start();
        thread2.start();
    }
}

class MyThread implements Runnable {
    public void run() {
        for (int i = 0; i < 10; i++) {
            System.out.println(Thread.currentThread().getName() + " : " + i);
        }
    }
}

import java.util.ArrayList;
import java.util.Iterator;

public class CollectionExample {
    public static void main(String[] args) {
        ArrayList<String> list = new ArrayList<String>();
        list.add("Java");
        list.add("Python");
        list.add("C++");
        
        Iterator<String> iterator = list.iterator();
        while (iterator.hasNext()) {
            System.out.println(iterator.next());
        }
    }
}

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;

public class IOExample {
    public static void main(String[] args) {
        try {
            BufferedReader reader = new BufferedReader(new FileReader("input.txt"));
            BufferedWriter writer = new BufferedWriter(new FileWriter("output.txt"));

            String line;
            while ((line = reader.readLine()) != null) {
                writer.write(line);
                writer.newLine();
            }

            reader.close();
            writer.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}