Custom lock incrementation

package multithreading.lock;

public class CustomLock {

    private boolean isLocked = false;

    public void lock() throws InterruptedException {
        synchronized(this) {
            while(isLocked) wait();
            isLocked = true;
        }
    }

    public void unlock() {
        synchronized(this) {
            if(isLocked) {
                isLocked = false;
                notify();
            }
        }
    }
}

package multithreading.lock;

public class SomeObject {

    private final CustomLock lock = new CustomLock();

    public long count = 0;

    public void inc() throws InterruptedException {
        lock.lock();
        count++;
        lock.unlock();
    }
}

package multithreading.lock;

import java.util.ArrayList;
import java.util.List;

public class Client {

    public static void main(String[] args) {
        SomeObject someObject = new SomeObject();

        List<Thread> threads = new ArrayList<>();

        for (int i = 0; i < 500_000; i++) {
            threads.add(new Thread(() -> incTask(someObject), "Thread " + i));
        }

        threads.forEach(Thread::start);

        // Join all threads to complete
        threads.forEach(thread -> {
            try {
                thread.join();
            } catch (InterruptedException e) {
                throw new RuntimeException(e);
            }
        });

        System.out.println(
                "Value of count is " + someObject.count
        );
    }

    private static void incTask(SomeObject someObject) {
        try {
            someObject.inc();
        } catch (InterruptedException e) {
            throw new RuntimeException(e);
        }
    }
}