Crazy java study notes a

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java data types

1.java basic data type and reference types into
eight basic types:
byte, char, Boolean, Short, int, Long, a float, Double
reference types:
in memory address value is represented by: a class name @ 16 hex memory address
2.java 8 provides a basic type packaging corresponding to
Byte, Character, Boolean, Short, Integer, Long, the Float, Double
3. special class
String, modified final immutable class
4. macro variables
in compile-time can be determined, immutable
Final H String = "the Hello";
Final W String = "World"
String HW = H + W;
5.String constants stored in the constant pool
String = L "look";
6. the array ( storing primitive types and application type)
array is the most basic java container class, is a linear data storage.
two-dimensional array (multidimensional array)
7 collections (containers) storage type reference
collection collections collection tool
linear List , ArrayList, Vector, LinkedList, Dequen , Quen, Set, HashSet, LinkedHashSet, TreeSet
key-value对 Map HashMap HashTable LinkedHashMap TreeMap