Few points for consideration:

• You can achieve it by using Synchronization or thread-safe.

• You are using synchronization in your code which is correct. But you are trying to use same Scanner object across multiple threads. Scanner is not thread-safe. Each thread should ideally use its own scanner or you should synchronize access to the Scanner.

• You are calling addingForFirstList for all threads, which means you are adding values to wrong lists. You should call appropriate method for each list.

• You are using separate locks for each list, which is correct and it ensures each list is accessed independently.

• You may also consider Executor Framework, which provides high-level API for managing threads. And it's crucial to manage shared resources like Scanner