java面相对象学习笔记

private 权限修饰符

被private修饰的成员只能在本类中访问

App类

public class App {
        private String AppName;
        private int App;
        private double app;

        public void setAppName(String name){
            AppName = name;
        }
        public String getAppName(){
            return AppName;
        }
          //给成员变量赋值的
        public void setApp(int app){
            App=app;
        }
          //从外调用App属性的
        public int getApp(){
            return App;
        }

        public void setapp(double appdouble){
            app=appdouble;
        }
        public double getapp(){
            return app;
        }
        public void sout(){
            System.out.println("这是一个测试");
        }

    
}

App测试类

public class AppTest {
    public static void main(String[] args) {
        App test = new App();
        test.setApp(12);
        test.setapp(12.0);


        int App=test.getApp();
        test.setAppName("test");       //用setAppName方法给App赋值
        String Appname=test.getAppName(); //用getAppName方法调用App属性
        System.out.println(App);
        System.out.println(Appname);

    }
     
}

this关键字

this可以区分成员变量和局部变量

App类

public class App {
        private String AppName;
        private int App;
        private double app;

        public void setAppName(String AppName){
            this.AppName = AppName;
        }
        public String getAppName(){
            return AppName;
        }

        public void setApp(int App){
            this.App=App;
        }//this.App是private int App(成员变量)，App表示的是局部变量
        public int getApp(){
            return App;
        }

        public void setapp(double app){
            this.app=app;
        }
        public double getapp(){
            return app;
        }
        public void sout(){
            System.out.println("这是一个测试");
        }

    
}

App测试类

public class AppTest {
    public static void main(String[] args) {
        App test = new App();
        test.setApp(12);
        test.setAppName("test");
        test.setapp(12.0);


        int App=test.getApp();
        String Appname=test.getAppName();
        System.out.println(App);
        System.out.println(Appname);

    }
     
}

构造方法

App类

public class App {
        private String AppName;
        private int App;
        private double app;

        public App(){

        }//空参构造方法
    
    //如果已经定义了构造方法，系统将不再提供默认的构造方法，所以无论是否使用，都要手写无参构造方法和带全部参数的构造方法
    
        public App(String AppName,int App,double app){
            //带参构造方法
            this.AppName = AppName;
            this.App = App;
            this.app = app;
        }//写了带参构造方法就可以不用再写set方法了
        
        public String getAppName(){
            return AppName;
        }
        public int getApp(){
            return App;
        }
        public double getapp(){
            return app;
        }

    
}

App测试类

public class AppTest {
    public static void main(String[] args) {
        App test = new App("test",12,12.0);
        
        //写了带参构造方法，可以直接调用get方法
        int App=test.getApp();
        String Appname=test.getAppName();
        
        System.out.println(App);
        System.out.println(Appname);

    }
     
}

App类，标准JavaBean

package exa;

public class App {
    private String user;
    private int Password;
    private int corppassword;
    private String email;
    private int ord;

    //空参
    public App(){

    }

    //带全部参数
    public App(String user,int Password,int corppassword,String email,int ord){
        this.user=user;
        this.Password=Password;
        this.corppassword=corppassword;
        this.email=email;
        if(ord>=19&&ord<=25){
            this.ord=ord;  
        }

    }

        //get和set
    public String getUser() {
        return user;
    }

    public void setUser(String user) {
        this.user = user;
    }

    public int getPassword() {
        return Password;
    }

    public void setPassword(int Password) {
        this.Password = Password;
    }

    public int getCorppassword() {
        return corppassword;
    }

    public void setCorppassword(int corppassword) {
        this.corppassword = corppassword;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }

    public int getOrd() {
        return ord;
    }

    public void setOrd(int ord) {
        this.ord = ord;
    }
 
}

使用alt+insert或alt+fn+insert可以一键生成，空参构造方法，带参构造方法，get和set，(vscode要安装IntelliJ IDEA Keybindings才能使用和idea一样的快捷健)

App测试类

package exa;

public class AppTest {
    public static void main(String[] args) {
        App test = new App("xiaoliu", 123456,123456, "3509342843@qq.com", 20);
        int ord = test.getord();
        String user = test.getuser();
        int Password = test.getcorppassword();
        System.out.println(Password);
        System.out.println(user);
        System.out.println(ord);
    } 
}