class area
{
double a,b;
double area;
public area(double x,double y)
{
a=x;
b=y;
}
public double setarea(double x,double y){
a=x;
b=y;
return a;
}
public double getarea(){
return a;
}
public double Toarea(double x,double y)
{
return area=0.5*a*b;
}
public String areais()
{ String s;
return s="面积为:"+area;
}
}
public class testarea
{
public static void main(String[]args)
{ area c=new area();
c.Toarea(1.0,2.0);
c.areais();
System.out.println("面积为:");
}
}
{
double a,b;
double area;
public area(double x,double y)
{
a=x;
b=y;
}
public double setarea(double x,double y){
a=x;
b=y;
return a;
}
public double getarea(){
return a;
}
public double Toarea(double x,double y)
{
return area=0.5*a*b;
}
public String areais()
{ String s;
return s="面积为:"+area;
}
}
public class testarea
{
public static void main(String[]args)
{ area c=new area();
c.Toarea(1.0,2.0);
c.areais();
System.out.println("面积为:");
}
}
area c=new area(); 应该改成area c=new area(数字1,数字2);
原因是你显示定义了有参构造,类默认的无参构造将不起作用。
好好看看书
应该就有结果了