java-thread-safe and non-thread-safe differences in understanding

1. ArrayList: The bottom layer is the array structure, Query Fast, adding and deleting slow

linkedlist: The underlying structure is linked list, query slow , delete quickly

2. Thread-safe and non-thread-safe

non-thread-safe refers to a problem that can occur with multithreaded operations on the same object .

thread Safety is not a problem with multithreaded operations on the same object .

Thread safety must use many synchronized keywords to synchronize control, so it inevitably leads to degraded performance.

ArrayList is non-thread-safe, vector is thread-safe

HashMap is non-thread-safe, Hashtable is thread-safe

StringBuilder is non-thread-safe, StringBuffer is thread-safe

java-thread-safe and non-thread-safe differences in understanding