封装

面向对象的三大特征:封装，继承，多态。
封装:告诉我们，如何正确设计对象的属性和方法。
封装的原则:对象代表什么，就得封装对应的数据，并提供数据对应的行为。

基本概念

画圆需要的是圆的属性，是圆的行为。

门被关，李四被噶

总结

1.什么是封装啊?
告诉我们，如何正确设计对象的属性和方法。
原则:对象代表什么，就得封装对应的数据，并提供数据对应的行为。
2.理解封装思想有什么好处?
让编程变得很简单，有什么事，找对象，调方法就行。
降低我们的学习成本，可以少学、少记，或者说压根不用学，
不用记对象的那么多方法，有需要时去找就行

如何更好的封装

package com.itheima.encapsulation;

public class Student {
    private int age;

    public void setAge(int age){
        if(age>=0&&age<=200){
            this.age=age;
        }else{
            System.out.println("您的年龄数据有问题！");
        }
    }

    public int getAge(){
        return age;
    }
}

package com.itheima.encapsulation;

public class Test {
    public static void main(String[] args) {
        Student s =new Student();
        s.setAge(-23);
        System.out.println(s.getAge());
    }

}

总结

1．如何进行更好的封装?

• 一般会把成员变量使用private隐藏起来，对外就不能直接访问了。
• 提供public修饰的getter和setter方法暴露其取值和赋值。

JavaBean

package com.itheima.javabean;

public class User {
    private String name;
    private double height;
    private double salary;

    public User() {
    }

    public User(String name, double height, double salary) {
        this.name = name;
        this.height = height;
        this.salary = salary;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public double getHeight() {
        return height;
    }

    public void setHeight(double height) {
        this.height = height;
    }

    public double getSalary() {
        return salary;
    }

    public void setSalary(double salary) {
        this.salary = salary;
    }
}

package com.itheima.javabean;

public class Test {
    public static void main(String[] args) {
        User u1 = new User();
        u1.setName("吴彦祖");
        u1.setHeight(180.5);
        u1.setSalary(1000.0);
        System.out.println(u1.getName());
        System.out.println(u1.getHeight());
        System.out.println(u1.getSalary());

        User u2 = new User("古天乐",175,300000);
        System.out.println(u2.getName());
        System.out.println(u2.getHeight());
        System.out.println(u2.getSalary());
    }
}

补充知识：成员变量，局部变量区别

综合案例

package com.itheima.moviedemo;

public class Movie {
    private String name;
    private double score;
    private String actor;

    public Movie() {
    }

    public Movie(String name, double score, String actor) {
        this.name = name;
        this.score = score;
        this.actor = actor;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public double getScore() {
        return score;
    }

    public void setScore(double score) {
        this.score = score;
    }

    public String getActor() {
        return actor;
    }

    public void setActor(String actor) {
        this.actor = actor;
    }
}

package com.itheima.moviedemo;

public class Test {
    public static void main(String[] args) {
        Movie [] movies = new Movie[3];

        movies[0]= new Movie("长津湖",9.7,"吴京");
        movies[1]= new Movie("我和我的父辈",9.6,"吴京");
        movies[2]= new Movie("扑水少年",9.5,"王川");

        for(int i =0;i<movies.length;i++){
            Movie m = movies[i];
            System.out.println(m);
            System.out.println("电影名:"+m.getName());
            System.out.println("得分："+m.getScore());
            System.out.println("主演:"+m.getActor());
            System.out.println("-----------------");
        }
    }
}