Java learning 9--Object-oriented

(Focus: Memory analysis)

Definition of Class

1 //define a class with the class keyword2 classPerson {3     //member Variable definition4     Private intID;5     Private intAge = 20;6     //method Definition7      Public intGetage () {8         returnAge ;9     }Ten      Public voidSetage (inti) { OneAge =i; A     } -      Public intgetId () { -         returnID; the     } -}

Member variables

1. member variables can use any of the data types in the Java language (including basic types and reference types);

2, the function of the member variable is the whole class body;

3, the member variable can be initialized when it is defined, and if not initialized, Java uses the default value to initialize it.

Reference

1. Variable types other than basic types in the Java language are referred to as reference types.

2. Manipulating objects by reference in Java

1 // declares a reference variable of type string, but does not point it to an object 2 String S; 3 // use the new statement to create a string object and point it to it to complete its operation with s 4 New String ("Hello world!!");

Construction method

1. Create a new object by using New + construction method

2. A constructor is a function that is defined in a Java class to initialize an object

3. The constructor has the same name as the class and no return value

4. When a constructor is not specified, the compiler automatically adds a default constructor for the class

1  Public classPerson {2     Private intID;3     Private intAge = 20;4     //constructor Function5Person (intNinti) {6ID =N;7Age =i;8     }9      Public Static voidMain (String args[]) {Ten         //use constructors to initialize the object's member variables when creating an object OnePerson Tom =NewPeron (1, 25); A     } -}

Overloading of methods

1. A class can define multiple methods with the same name and return type, but with different parameters (number and type).

2, when called, the corresponding method will be selected according to the different parameter table

3. Overloads that can also be used to construct functions

1  Public classPerson {2     Private intID;3     Private intAge = 20;4     //constructor Function5Person (intNinti) {6ID =N;7Age =i;8     }9 Ten     voidinfo () { OneSYSTEM.OUT.PRINTLN ("My ID is" +ID); A     } -  -     //Overloaded Info Method the     voidinfo (String t) { -System.out.println (t + "ID is" +ID); -     } -  +      Public Static voidMain (String args[]) { -         //use constructors to initialize the object's member variables when creating an object +Person Tom =NewPeron (1, 25); A p.info (); atP.info ("Lily"); -     } -}

Recommended naming rules

1, the first letter of the class name capital

2. The first letter of the variable name and method name is lowercase

3, the use of hump marking

Java learning 9--Object-oriented