类的修饰符

public class JuXin {
    


    //    double chang;
//    double kuan;
//    
//    JuXin()
//    {
//        chang=10;
//        kuan=5;
//    }
//    
//    double getMianJi()
//    {
//        return (chang*kuan);
//    }
//    
//    public static void main(String[] args)
//    {
//        JuXin myJX=new JuXin();
//        System.out.println("矩形的面积是："+myJX.getMianJi());
//    }
//
    //私有的   本类内部才能用
    private double chang;
   
    //默认修饰符，保护，本包内用
    //protected double kuan;
     double kuan;

    

    

    
    
    
    
    public double getChang()
    {
        return chang;
    }
    public double getKuan()
    {
        return kuan;
    }
    
    
    
    
    public void setChang(double chang)
    {
        //加上验证
        if(chang>0)
        {
            this.chang=chang;
        }
        else
        {
            System.out.println("长度值"+chang+"无效");
        }
    }
    
    public void setKuan(double kuan)
    {
        if(kuan<=0)
        {
            System.out.println("宽度值"+kuan+"无效");
        }
        else
        {
            this.kuan=kuan;
        }
    }
    
    public JuXin()
    {
        
    }
    
    
    
    
   public JuXin( double chang,double kuan)//包外用，加public
    {
//        this.chang=chang;
//        this.kuan=kuan;
       setChang(chang);
       setKuan(kuan);
        
    }
   public double getMianJi()
    {
        return chang*kuan;
    }
    
    //公共的
    public static void main(String args[])
    {
        JuXin myJx=new JuXin(20,6);
        System.out.println("长："+myJx.chang);
        System.out.println(myJx.getMianJi());
        
    }



    public static void main1(String[] args) {
        
        //juxing.JuXin myJX2=new JuXin();
        JuXin myJX1=new JuXin(20,6);//外部用，在原先类创建，加public

        
        
        
        //读取属性值，不能修改,开放
//        public double getChang()
//        {
//            return chang;
//        }
//        public double grtKuan()
//        {
//            return kuan;
//        }
        System.out.println("宽="+myJX1.getKuan());
        System.out.println("长="+myJX1.getChang());
        
        JuXin myJx2=new JuXin();
        
        myJx2.setChang(30);
        myJx2.setKuan(15);
        
        System.out.println("矩形面积："+myJx2.getMianJi());




public static void main(String[] args) {
        
        //juxing.JuXin myJX2=new JuXin();
        JuXin myJX1=new JuXin(20,6);//外部用，在原先类创建，加public

        
        
        
        //读取属性值，不能修改,开放
//        public double getChang()
//        {
//            return chang;
//        }
//        public double grtKuan()
//        {
//            return kuan;
//        }
        System.out.println("宽="+myJX1.getKuan());
        System.out.println("长="+myJX1.getChang());