Object-oriented
Process Oriented (pop)
Analyze the specific implementation steps to achieve step by step
Object-oriented (oop->object-oriented programming)
Think and solve problems in a classified way, analyze and classify things as a whole
Case: Put the elephant in the refrigerator
Process-oriented thinking
1. Open the refrigerator door
2. Pack the elephant in
3. Close the refrigerator door
Object-oriented thinking
Design category:
1. Human (load stuff)
2. Elephant
3. Refrigerator (to store things)
4.Door (open door, close door)
Object-oriented is also inseparable from process-oriented, and the implementation of specific details is still process-oriented
Java class
A class is a template, which defines the common attributes and characteristics of a class object (object), and creates a file (.java class) to record this information.
Class definition:
The structure of the class:
Variables: description of the properties of things;
Method: the behavior of things;
Construction method: used to create objects;
Inner class: the class declared in the class body;
Block: A code block without a name
Design category:
1. Discover the class grammar
2.Define the attributes, characteristics, and variables of the class
3. Define the behavior, function, and method of the class
/**
* 发现类
* [访问权限修饰符] [修饰符] class(定义类) 类名 {
* 变量：事物属性的描述；
* 方法:事物的行为；（可以做的事情）
* 构造方法：用于创建对象；
* 内部类： 即在类体中声明的类。
* 块：一段没有名称的代码块
* }
* 访问修饰符有两种 public 或者 不写
* 修饰符: final , abstract
* 类名: 类名首字母大写,见名知意,驼峰表示
*/
public class People {
/**
* 发现共有属性
* 成员变量定义
* [访问权限修饰符] [修饰符] type 变量名;
*/
String name;
String sex;
int age;
/**
成员方法
人有睡觉吃饭学习等行为
[访问权限修饰符] [修饰符]/void 方法名(参数类型 参数名){
sout();
[return 返回值;]
}
*/
/*睡觉的方法*/
public void Sleep() {
System.out.println(name + "说费觉觉");
return;
}
/* 吃饭的方法*/
public void Eat() {
System.out.println(name + "说开饭了,冲冲冲");
}
/*学习的方法*/
public void Study() {
System.out.println(name + "说一秒不学习,浑身难受");
}
}
Java objects
An object is an instance of a class, which is an actual instance created in memory by the class as a template.
An object is actually an instance of concrete existence, and creating an object is to instantiate an object
/*
类定义好后,是一个文件,但不能使用
以类为模板创建对象,对象是实例,视具体存在的,可以被使用
People cui = new People();
new + People 类的构造方法,在内存中创建一个具体的对象
People cui 以People类为类型声明一个变量cui
= 让cui变量 指向(引用)内存中的对象
cui.name = "张三";
使用cui变量 . 调用对象中的属性(变量)\行为(方法)
*/
People zhang = new People();
zhang.name = "张三";
zhang.age = 21;
zhang.sex = "男";
System.out.println("姓名:" + zhang.name + "\t性别:" + zhang.sex + "\t年龄:" + zhang.age);
zhang.Eat();
zhang.Sleep();
zhang.Study();
Variable classification
Divided by data type:
Basic types: 8 types
Reference data type: class as type, array
Classified by location:
Member variables: properties of things
Defined in the class, outside the method body
All data types supported in java can be used
It is not necessary to initialize and assign values. When creating an object, the virtual machine assigns values by default.
String :null char:" " int:0 Boolean:false
Member variables can be accessed in member methods
Local variables: the behavior of things
Defined in methods, constructors, and code blocks, supporting all data types
Initialize the assignment before use, and the variable will be destroyed after the method ends
Method classification
Member method
/*
成员方法
[访问权限修饰符] [修饰符] [返回值类型]/void 方法名(参数类型 参数名){
语句块
[return 值]
}
*/
public void Sleep() {
System.out.println(name + "说费觉觉");
return;
}
//int day,String deep 方法参数也是局部变量
public void Play(int day,String deep){
System.out.println(name+deep+"使劲玩");
}
People zhang = new People();
//成员方法必须通过对象调用
zhang.Sleep();
zhang.Play(22222,"哈哈哈哈");