No lock - biased locking - Lightweight lock (spinlocks CAS) - heavyweight lock
1. biased locking
Specific to a thread, a biased locking thread, such as thread id
2. Lightweight lock
When there are multiple threads competing for a lock, the lock upgrade lightweight, the stack pointer to the record, a process known as CAS
3. heavyweight lock
When competing threads more than 10 times, upgraded to heavyweight lock, user mode to kernel mode to upgrade the efficiency of slow