1. Object-Oriented (construction method constructor Overview and format)
- A: Overview and role of construction methods
- Initialize the object's data (properties)
- B: Construction Method Format features
- A: The method name is the same as the class name (the size should also match the class name)
- B: No return value type, not even void
- C: No specific return value returned;
2. Object-oriented (overloading of construction methods and precautions)
- A: Case Demo
- Overloading of construction methods
- Overloading: Method names are the same, regardless of the return value type (construction method has no return value), see only the parameter list
- B: Construction Method considerations
- A: If we do not give a construction method, the system will automatically provide a non-parametric construction method.
- B: If we give a construction method, the system will no longer provide a default parameterless construction method.
- Note: This time, if we still want to use the parameterless construction method, we have to give it ourselves. It is recommended that you always give the method of non-parametric construction
3. Object-oriented (the difference between two ways to assign a value to a member variable)
- A:setxxx () method
- modifying property values
- B: Construction method
- To initialize an attribute in an object
4. Object-oriented (code and test of student Class)
07.05_ Object-oriented (code and test of mobile phone Class) (master)
- A: Case Demo
- Imitate the student class, complete the phone class code
6. Object-oriented (steps to create an object)
- A: Drawing Demo
- Drawing describes what has been done during the creation of an object?
- Student s = new Student ();
- 1,student.class Loading into memory
- 2, declaring a student type reference s
- 3, the object is created in heap memory,
- 4, default initialization value for property in Object
- 5, the property is displayed for initialization
- 6, constructs the method into the stack, assigns the value to the attribute in the object, constructs the method the bomb stack
- 7, assign the object's address value to s
7. Object-oriented (rectangular case practice)
- A: Case Demo
- Demand:
- Defines a rectangle class that defines the method for calculating the circumference and area,
- Then define a test class to test.
8, Object-oriented (Employee class case practice)
- A: Case Demo
- Requirements: Define an employee class employee
- Analyze several members yourself and then give the member variables
- Name Name, work number ID, payroll salary
- Construction method,
- Null parameter and the argument
- GetXxx () setxxx () method,
- And a way to display all of the member information. and tested.
9. Object-oriented (static keyword and memory map)
A: Case Demo
- Introduce the static keyword through a case.
- Human: person. Everyone has a nationality, China.
B: Drawing Demo
- Memory diagram with Static
10. Object-oriented (characteristics of the static keyword)
- Features of the A:static keyword
- A: Loaded with the load of the class
- B: Precedence over object existence
- C: Shared by all objects of the class
- Example: Students in our class should share the same class number.
- In fact, this feature is also telling us when to use static?
- If a member variable is shared by all objects, it should be defined as static.
- Example:
- Water dispenser (with static modification)
- Water Cup (cannot be modified by static)
- Common use static, non-static characteristics
- D: Can be called by the class name
- In fact, it can also be called by the object name itself.
- It is recommended to call with the class name.
- Content that is statically modified is generally referred to as: Class-related, Class-member
- B: Case Demo
- Features of the Static keyword
11. Object-oriented (static considerations)
- A:static precautions
- A: There is no this keyword in the static method
- How to understand it?
- Static is loaded as the class loads, and this is present as the object is created.
- Static than object exists first.
- B: Static methods can only access static member variables and static member methods
- static method:
- Member variables: Only static variables can be accessed
- Member method: Only static member methods can be accessed
- Non-static methods:
- Member variable: can be static or non-static
- Member method: However, it is a static member method or a non-static member method.
- Easy to remember:
- Static can only be accessed statically.
- B: Case Demo
- Considerations for Static
12. Object-oriented (the difference between static variables and member variables)
- A static variable is also called a class variable member variable also called an object variable
- A: Belong to different
- Static variables belong to classes, so they are also referred to as class variables
- Member variables belong to an object, so also known as instance variables (object variables)
- B: Different locations in memory
- Static variables stored in the static area of the method area
- member variables stored in heap memory
- C: Memory occurrence time is different
- Static variables are loaded as the class is loaded and disappear as the class disappears
- Member variables exist as the object is created and disappear as the object disappears
- D: Call Different
- A static variable can be called by a class name, or it can be called by an object
- Member variables can only be called by object name
13. Object-oriented (the format of the main method is explained in detail)
- A: Format
- public static void Main (string[] args) {}
- B: Explanation of the format
- Public is called by the JVM, and access permissions are large enough.
- Static is called by the JVM without creating objects, accessing the class name directly
- Void is called by the JVM and does not need to return a value to the JVM
- Main a generic name, although not a keyword, but is recognized by the JVM
- String[] args was previously used to receive keyboard input
- C: Demo Case
- Receiving keyboards via args such as data
14. Object-oriented (use static in tool Class)
- A: Make a tool class
- Arraytool
- 1, gets the maximum value
- 2, the traversal of the array
- 3, the inverse of the array
15, object-oriented (the production process of the manual)
- A: Add A document Comment to the tool class
- B: Generate instructions by Javadoc command
- @author (extract author content)
- @version (extract version content)
- javadoc-d the specified file directory-author-version Arraytool.java
- @param parameter name//variable name of formal parameter @return function runs out of returned data
16. Object-oriented (how to use the Help document provided by the JDK)
- A: Locate the document, open the document
- B: Click on the display, find the index, the input box appears
- C: You should know who you're looking for. Example: Scanner
- D: Look at the structure of this class (requires no guide package)
- Member Variable fields
- Constructing methods of construction method
- Member Method methods
17. Object-Oriented (learn the random number function of math class)
- Open the help documentation provided by the JDK to learn
- A:math class overview
- class contains methods for performing basic mathematical operations
- B:math class Characteristics
- Because the math class is under the Java.lang package, there is no need for a guide package.
- Because its members are all static, private construction methods
- C: Method of obtaining a random number
- public static Double Random (): Returns a double with a positive number that is greater than or equal to 0.0 and less than 1.0.
- D: I'm going to get a random number between 1-100, swollen?
- int number = (int) (Math.random () *100) +1;
18_ Object-oriented (guess digital mini-game case)
- A: Case Demo
- Need: Guess number games (data between 1-100)
Java EE Basics (vii)
