Overview timing of load and load class:
A: Overview
When you want to use a class if the class has not yet been loaded into memory, the system by loading, connect, initialize three steps to achieve this class is initialized
load
The class file is read into memory, and whom to create a Class object. Any class that will be used by the system to create a class object
connection
Verify that the correct internal structure, and coordinated with other classes
Responsible for the preparation of a static class members to allocate memory and set the default initialization value
Parsing the binary data class is replaced symbolic references direct reference
initialization
It is the initialization step
B: Load opportunity
Create an instance of the class
Access class static variable or static variable assignment
Static method call class
Using reflection to create a way to force the class or interface objects corresponding java.lang.class
Initiating a subclass of class
Direct use java.exe command to run a master class
Class loader and an overview of the classification:
A: Overview
Responsible for loading .class file into memory for, and generate the corresponding class object.
B: Classification
Bootstap ClassLoader root class loader
Extension ClassLoader extension classloader
System ClassLoader system class loader
C: Role
Bootstap ClassLoader root class loader
Also known as the bootstrap class loader is responsible for loading java core classes
Such as System, String. In rt.jar file under the JDK jre lib directory
Extension ClassLoader extension classloader
JRE extensions directory is responsible for loading the jar package
In the JDK jre lib directory under ext directory
System ClassLoader system class loader
Responsible for loading class files from the java command, and classpath environment variable specified jar package and class path when JVM startup
Reflection Overview:
A: Overview
JAVA reflection really operating state, for any class, are made known to all properties and methods of this class
For any object, you can call any of its methods and properties
Reflection function of this approach and the dynamic invocation object information acquired dynamically called java language
To Anatomy of a class, you must first get to the bytecode file object class
The class's method is used in anatomy, so first acquired each object class bytecode files corresponding to the type of
B: three ways
a: getClass Object class () method, it is determined whether the two objects are the same bytecode files
b: static property class. Lock objects
c: forName class class static method (), reads the configuration file
class.forName () reads the configuration file example:
Juicer
Obtaining parameters configured by a reflection method using:
Constructor
Obtain and use the member variables by reflection:
Field
By using the method for obtaining and reflecting:
Method
By reflection across the generic inspection:
Write a generic set of an object by reflecting a property value specified:
Exercise:
Dynamic Agent overview and implementation:
A: Overview
Agent: things could have been done yourself, others do, was asked who is the proxy object
Dynamic Agent: generating the object program is running, dynamic proxies in fact be generated by reflecting a proxy
Overview template design patterns and use:
A: Overview
Template Method is to define the skeleton of an algorithm, the algorithm will be specific to subclasses to achieve a delay
B: advantages and disadvantages
a: the advantages
Template Method pattern, the definition of the algorithm in the skeleton at the same time, can be very flexible to achieve specific algorithm to meet user demand for flexible
b: shortcomings
If the algorithm has to modify the skeleton, then you need to modify the abstract class
JDK5 new features (own implementation enumerated classes):
A: Overview
Refers to the value of the variable to be listed, the value of the variable is limited within a range of values enumerated.
B: Recall singleton design pattern: singleton instance of a class has only one
Example much class is a class has multiple instances, but not an infinite number of examples, but the limited number of examples. This order is an enumeration class
C：Demo
Achieved by enumeration class enum:
Note enumeration:
Enumeration class that defines use keyword enum
All of the enumeration classes are subclasses of Enum
On the first line enumeration class must enumeration, enumeration semicolon after the last entry can be omitted, but if there are other things enumeration class, the semicolon can not be omitted. Best not to omit
Enum class can have a constructor, but it must be private, and it's the default is private
Enum class can have abstract methods, but enumeration must override this method
A common method of enumeration class:
JDK7 of six new features:
A: binary literals
B: numeric literals can be underlined
C: switch statement can use the string
D: Generic simplified, generic diamond
E: abnormal multiple catch merger, each with abnormal or |
F: try-with-resources statement
JDK8 new features:
Interface may be defined with a body methods, if modified non-static, default must
If you do not have to be static