The difference between java--string and StringBuilder, StringBuffer?

1.String is a read-only string, and the referenced string content cannot be changed.

The string objects of 2.StringBuffer and StringBuilder can be modified directly.

3.StringBuilder is not modified by synchronized keyword, thread is unsafe, efficiency is higher than stringbuffer,stringbuffer thread safety.

4. If the resulting string is already present in the static store, the "+" performance is better than the Stringbuffer/stringbuilder append method.

The difference between java--string and StringBuilder, StringBuffer?