Package, modifier, inner class, Anonymous inner class (Java Basics 10)

Overview and role of 1.package keywords

* A: Why should I have a bag
* Classify the byte code (. Class)
* B: Overview of the Package
*
* C: The role of the package
* Package name to be defined in the first line,
* Package name. * All classes under this package are visible
* Concrete analogy is better, can improve efficiency

2. Package Definition and Precautions

* A: Define the format of the package
* Package name;
* Multi-stage pack. Separate
* B: Considerations for defining packages
* The A:package statement must be the first executable code of the program
* B:package statements can only have one in a Java file
* C: If there is no package, default means no packages (previously defined classes do not have a package name)
* C: Case Demo
* Package Definition and Precautions

Overview and use of 3.import keywords

* A: Case Presentation
* Why should I have an import
* B: Guide Package format
* Import Package name (all-inclusive name);
Note
* This way the import is to the name of the class.
* Although can be written last *, but not recommended.
* C:package,import,class There is no sequential relationship (interview question)
* First line of package, import second, class third

4. Common modifiers used by the class and its composition

* A: modifier:
* Permission modifier: private, Default (Defalut), protected,public
* Status modifier: static,final
* Abstract modifier: Abstraction
* B: Class:
* Permission modifier: default modifier, public
* Status modifier: Final
* Abstract modifier: Abstraction
* The most used is: public
* C: Member Variable:
* Permission modifier: private, default, Protected,public
* Status modifier: static,final
* The most used is: private
* D: Construction Method:
* Permission modifier: private, default, Protected,public
* The most used is: public
* E: Member Method:
* Permission modifier: private, default, Protected,public
* Status modifier: static,final
* Abstract modifier: Abstraction
* The most used is: public
* F: In addition to the combination of rules:
* Member variable: public static final
* Member Method:
* public static
* Public abstract
* Public Final

5. Internal class overview and accessibility features

A: Internal class overview
*
* B: Internal class Access features
* A: The inner class can access the members of the external class directly, including the private.
* B: External class to access members of an inner class, you must create an object.

6. Internal class classification and direct use of members ' internal classes

* A: According to the internal class location classification
* Member Location: The class defined in the member location, called the member inner class.
* Local location: The class defined in the local location, called the local inner class.
* B: Member Inner class
* How to access the members of the inner class directly in the test class.
* External class name. Internal class Name Object name = External Class object. Inner class object;

7. Common modifiers and applications of members ' inner classes

* A: Modifier of the member's inner class:
* Private to ensure the security of the data
* Static for easy access to data
* Note: External class data accessed by static internal classes must be statically decorated.
* B: The member inner class is accessed by statically modifying the following methods:
* External class name. Internal class Name Object name = new External class name. Internal class name ();
* Static members cannot be defined in a non-static member inner class

8. The face question of the members ' inner class

Requirements: Use known variables in the console output 30,20,10. classOuter { Public intnum = 10; classInner { Public intnum = 20;  Public voidShow () {intnum = 30;                    SYSTEM.OUT.PRINTLN (num); System.out.println ( This. Num); System.out.println (Outer. This. Num); }            }        }        classInnerclasstest { Public Static voidMain (string[] args) {Outer.Inner Oi=NewOuter ().NewInner ();            Oi.show (); }            }

* Local internal classes access local variables, local variables must be final decorated.

9. The format and understanding of anonymous inner classes

* A: Anonymous inner class
* is a simplified notation of the inner class.
* B: Premise: There is a class or interface
* The class can be either a concrete class or an abstract class.
* C: Format:
*
New class name or interface name () {//Inherit this class or implement this class
Override method; overriding methods in a class or in an interface
}. Method name ();
* D: What is the essence?
* is an anonymous object that inherits the class or implements the interface's subclass.

10. Application of anonymous inner class in development

Write abstract classes Here, interfaces are OK
Abstract class Person {
public abstract void Show ();
}
Class Persondemo {
public void Method (person p) {
S.show ();
}
}
Class Persontest {
public static void Main (string[] args) {
How do I call method methods in Persondemo?
Persondemo PD = new Persondemo ();
Pd.method (new person () {
public void Show () {
System.out.println ("show");
}
});
}
}

11. Anonymous inner class of face question

according to the requirements, the CodeInterfaceInter {voidshow ();} classOuter { Public StaticInter Method () {return NewInter () { Public voidShow () {System.out.println ("Helloworld!");            }                }; }        }        classOuterdemo { Public Static voidMain (string[] args) {Outer.method (). Show (); //chained programming: The calling method returns an object, and you can continue to invoke the method}} requires output from the console "HelloWorld"

Package, modifier, inner class, Anonymous inner class (Java Basics 10)