18.12.15
Java a class can not implement two identical interfaces, compile-time error will be reported: Interface repeat
19.6.4
Constructor call sequence:
1. Call parent class constructor, from the beginning inherit the top down recursive
2. declaration order, call member class
Initialization method
3. Call the current class constructor body
The actual initialization process:
1. Before anything else happens, the storage space allocated to the object is initialized to binary zero
2. The order of constructor calls
19.6.5
Set——
HashSet: not stored in any order, but getting elements fastest - hash
TreeSet: the comparison result in ascending order - to use red-black tree
LinkedHashSet: added sorting order - use a hash, but the additional use of a linked list maintenance element insertion order
Each key can only be stored once Map--
HashMap: Find technology provides the fastest and disorderly
TreeMap: high Save button
LinkedHashMap: insertion order to save the key, while retaining the HashMap query speed