Java的封装

1 封装

封装：将类的某些信息隐藏在类内部，不允许外部程序直接访问，而是通过该类提供的方法来实现对隐藏信息的操作和访问。

封装的步骤

[1]属性私有化

[2]提供公共的设置器和访问器

[3]在设置器和访问器中添加业务校验逻辑

public class Dog{
	
	// 【1】private 私有的，对外不可见
	private String name;
	private int health;
	private int love;
	private String strain;

	// 【2】提供公共的设置器(setter)和访问器(getter)
	public void setName(String name){
		// 【3】逻辑校验
		if(name.equals("")){
			System.out.println("姓名不能为空.");
		}else{
			this.name = name;
		}
	}
	public String getName(){
		return this.name;
	}
	
	public void setHealth(int health){
		if(health < 0){
			System.out.println("健康值不合法.");
			this.health = 0;
		}else{
			this.health = health;
		}
	}
	public int getHealth(){
		return this.health;
	}
	
	public void setLove(int love){
		if(love < 0){
			System.out.println("亲密度不合法.");
			this.love = 0;
		}else{
			this.love = love;
		}
	}
	public int getLove(){
		return this.love;
	}
	
	public void setStrain(String strain){
		if(strain.equals("")){
			System.out.println("品种不能为空.");
		}else{
			this.strain = strain;
		}
	}
	public String getStrain(){
		return this.strain;
	}
	
	
	public Dog(){
		
	}

	public Dog(String name,int health,int love,String strain){
		this.setName(name);
		this.setHealth(health);
		this.setLove(love);
		this.setStrain(strain);
	}
	
	public void showInfo(){
		System.out.print("我的名字叫"+this.name);
		System.out.print(",健康值"+this.health);
		System.out.print(",亲密度"+this.love);
		System.out.println(",我是一只"+this.strain);
	}
}

 2 静态常量

果一个量的值不会发生改变，可以把该量声明为静态常量，用static final修饰。

public class Penguin{
    
    private String name;
    private int health;
    private int love;
    private String gender;
    
    static final String SEX_MALE = "雄";
    static final String SEX_FEMALE = "雌";
    
    public void setName(String name){
        this.name = name;
    }
    public String getName(){
        return this.name;
    }
    
    public void setHealth(int health){
        if(health>100 && health<1){
            this.health = 60;
            System.out.println("健康值必须在1-100之间，默认为60");
        }else{
            this.health = health;
        }
    }
    public int getHealth(){
        return this.health;
    }
    
    public void setLove(String love){
        this.love = love;
    }
    public int getLove(){
        return this.love;
    }
    
    public void setGender(String gender){
        this.gender = gender;
    }
    public String getGender(){
        return this.gender;
    }
    
    public Penguin(){
        
    }
    public Penguin(String name,String gender){
        this.setName(name);
        this.setGender(gender);
    }
    
    public Penguin(String name,int health,int love,String gender){
        this(name,gender);
        this.setHealth(health);
        this.setLove(love);
    }
    
    public void showInfo(){
        System.out.print("我的名字叫"+name);
        System.out.print(",健康值"+health);
        System.out.print(",亲密度"+love);
        System.out.println(",性别"+gender);
    }
    
    
}
public class Test02{
    public static void main(String[] args){
        
        Penguin penguin = new Penguin("大脚",100,0,Penguin.SEX_MALE);
    }
}