here are some multithreading exercises in Java that you can try:

1. Create a program that spawns multiple threads, each of which performs a different task. Use synchronization mechanisms to ensure that the threads execute in a specific order.

2. Create a program that implements a producer-consumer pattern. The program should have one or more producer threads that add items to a shared buffer and one or more consumer threads that remove items from the buffer.

3. Create a program that simulates a race between multiple threads. Each thread should represent a runner, and the race should be completed when all runners have finished. Use synchronization mechanisms to ensure that the runners do not interfere with each other.

4. Create a program that simulates a bank account. The program should have multiple threads that withdraw and deposit money from the account. Use synchronization mechanisms to ensure that the balance of the account remains consistent.

5. Create a program that implements a parallel quicksort algorithm. The program should use multiple threads to sort an array of numbers in parallel.

6. Create a program that downloads files from multiple URLs simultaneously. The program should use multiple threads to download the files and report the progress of each download.

7. Create a program that simulates a traffic intersection. The program should have multiple threads representing cars and traffic signals. Use synchronization mechanisms to ensure that the cars obey traffic signals and do not collide with each other.

These exercises can help you develop a better understanding of multithreading concepts in Java and improve your skills in writing efficient and reliable multithreaded applications.