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());