？？？

真受不了你们, 切图比看你们复制下来的代码好看..

class Airplane
{
Engine call = new Engine();
private String a;
public Airplane(String a)
{
this.a=a;
call.setType(a);
}
void showinfo()
{
call.getType();
}
}
class Engine
{
private String type;
public void setType(String type)
{
this.type=type;
}
public void getType()
{
if(type=="jet")
System.out.println("这是喷气式引擎");
else if (type=="PDAirplane")
System.out.println("这是螺旋桨引擎");
}
}
public class Plane
{
public static void main(String[]args)
{
Airplane jet=new Airplane("jet");
jet.showinfo();
Airplane PDAirplane=new Airplane("PDAirplane");
PDAirplane.showinfo();
}
}
把类Engine定义出来，为外部类
这样就可以了