instanceof

instanceof判断是否为某个类的对象实例

package polyMorphism;
 class Book {
 public void canBeRead(){
  System.out.println("All the books can be used for reading");
 }
 
}

package polyMorphism;
 class ComputerBook extends Book {
 public void canGetInfo(){
  System.out.println("The books about computer will lead you to a world about How CPU worked in your computer");
  
 }
}

package polyMorphism;
 class ComicBook extends Book{
  public void canBeFun()
  {
   System.out.println("Comic books are read for fun in my leisure time");
  }
}

package polyMorphism;
class checkPolyMorphism {
 public static void main (String [] args)
 {
  Book book1= new ComputerBook();
  Book book2= new Book();
  ComputerBook book3 = new ComputerBook();
  if (book1 instanceof ComputerBook)
   ((ComputerBook) book1).canGetInfo();
  if (book2 instanceof ComicBook)
   System.out.println(book2 instanceof ComicBook);
 // if (book3 instanceof ComicBook)
 //  System.out.println(book3 instanceof ComicBook);
 }
}

输出结果：

The books about computer will lead you to a world about How CPU worked in your computer