Question

java编程求错，求改！！

首先编写一个抽象类，要求该类有如下3个抽象方法：
public abstract void f(int x);
public abstract void g(int x,int y);
public abstract double h(double x);
然后分别给出该类的3个子类。要求：在应用程序的主类中使用这些子类创建对象，然后让他们的上转型对象调用方法：f(),g(),h()

abstract class A
{
public abstract void f(int x);
public abstract void g(int x,int y);
public abstract double h(double x);

}
class X extends A
{
public void f(int x)
{
System.out.println(x);
}
public void g(int x,int y)
{
System.out.println(x,y);
}
public double h(double x)
{
System.out.println(x);
}
}
class Y extends A
{
public void f(int x)
{
System.out.println(x);
}
public void g(int x,int y)
{
System.out.println(x,y);
}
public double h(double x)
{
System.out.println(x);
}
}
class Z extends A
{
public void f(int x)
{
System.out.println(x);
}
public void g(int x,int y)
{
System.out.println(x,y);
}
public double h(double x)
{
System.out.println(x);
}
}

public class P111_2
{
public static void main(String args[])
{
A a1;
a1=new X();
a1.f(10);

A a2;
a2=new Y();
a2.g(10,20);

A a3;
a3=new Z();
a3.h(10.0);
}
}

Answer 1

出错问题：1.System.out.println(x,y);错了 2.有些方法要返回值eg:return x;
修改后的代码：
abstract class A
{
public abstract void f(int x);
public abstract void g(int x,int y);
public abstract double h(double x);
}
class X extends A
{
public void f(int x)
{
System.out.println(x);
}
public void g(int x,int y)
{
System.out.println(x +" "+ y);
}
public double h(double x)
{
System.out.println(x);
return x;
}
}
class Y extends A
{
public void f(int x)
{
System.out.println(x);
}
public void g(int x,int y)
{
System.out.println(x +" "+ y);
}
public double h(double x)
{
System.out.println(x);
return x;
}
}
class Z extends A
{
public void f(int x)
{
System.out.println(x);
}
public void g(int x,int y)
{
System.out.println(x +" "+ y);
}
public double h(double x)
{
System.out.println(x);
return x;
}
}

public class P111_2
{
public static void main(String args[])
{
A a1;
a1=new X();
a1.f(10);

A a2;
a2=new Y();
a2.g(10,20);

A a3;
a3=new Z();
a3.h(10.0);
}
}

Answer 2

额，你不是已经给出实现代码了嘛

Answer 3

没太明白你的意思，你程序写错了？，这句话是什么意思：然后让他们的上转型对象调用方法：f(),g(),h()

Answer 4

你的system.out.println()出错了，这个方法只能有一个String参数，而你写的其中有两个，所以错了，你改成一个参数就行了