Java封装

1.什么是封装

封装可以认为是一个保护屏障，防止代码和数据被外部类定义的代码随机访问。封装最主要的功能在于我们可以修改自己的实现代码，而不用修改那些调用我们代码的程序片段。封装加强了代码的安全性。

2.封装的优点

1.良好的封装能够减少耦合性

3.实现封装的步骤

1. 修改属性的可见性来限制对属性的访问private

public class Person {    private String name;    private int age;}复制代码

2.对每个值属性提供对外的公共方法访问，使用get，set方法

public class Person{    private String name;    private int age;​    public int getAge(){      return age;    }​    public String getName(){      return name;    }​    public void setAge(int age){      this.age = age;    }​    public void setName(String name){      this.name = name;    }}复制代码

代码实例

public class Dog {	// 静态变量	private String name;	private int health;// 健康值	private int love;	private String strain;// 宠物的品种	public void show() {		System.out.println("我叫" + name + "，现在健康值是:" + health + ",亲密度是：" + love + ",品种是：" + strain);	}	public Dog() {	}	public Dog(int health, int love, String strain) {		this.health = health;		this.love = love;		this.strain = strain;	}	// 不能够轻易的可以通过对象名.属性名来修改数据 只提供一个方法给他 具体参数合法性判断由我们自己来决定	public void setHealth(int health) {		if (health < 0 || health > 100) {			System.out.println("健康值是0-100，默认值是60");			this.health = 60;			return;		}		this.health = health;	}	public int getHealth() {		return this.health;	}	public void setName(String name) {		this.name = name;	}	public String getName() {		return this.name;	}}复制代码

public class Demo02 {	public static void main(String[] args) {		// TODO Auto-generated method stub		Dog dog = new Dog();		// 封装属性 外部观察不到 只能看到相对应的方法 并且可以在方法里面实现控制		dog.setHealth(1001);		dog.setName("哈哈");		System.out.println(dog.getName());		System.out.println(dog.getHealth());		// 没有封装属性 可以随意的查看对象的属性		Dog2 dog2 = new Dog2();		dog2.health = -100;		dog2.show();	}}复制代码

public class Demo01 {	public static void main(String[] args) {		// TODO Auto-generated method stub		// 人有姓名 年龄 身高 体重 使用封装思想来创建类		Person person = new Person();		person.setName("张三");		person.setAge(18);		person.setHeight(175);		person.setWeight(130);		System.out.println(person.toString());	}}class Person {	private String name;	private int age;	private int height;	private int weight;	public String getName() {		return name;	}	public void setName(String name) {		this.name = name;	}	public int getAge() {		return age;	}	public void setAge(int age) {		this.age = age;	}	public int getHeight() {		return height;	}	public void setHeight(int height) {		if (height < 0) {			this.height = 0;			return;		}		this.height = height;	}	@Override	public String toString() {		return "Person [name=" + name + ", age=" + age + ", height=" + height + ", weight=" + weight + "]";	}	public int getWeight() {		return weight;	}	public void setWeight(int weight) {		if (weight < 0) {			this.weight = 0;			return;		}		this.weight = weight;	}}复制代码