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
2.类内部的结构可以自由修改
3.隐藏信息，增强安全性

3.实现封装的步骤

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;
}

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;
    }
}

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;

	}
}

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();
	}

}

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;
	}

}