instanceof与generic类的结合使用例子

class Gen<T> {      
  T ob;     
        
  Gen(T o) {      
    ob = o;      
  }      
      
  // Return ob.      
  T getob() {      
    return ob;      
  }      
}      
     
// A subclass of Gen.     
class Gen2<T> extends Gen<T> {     
  Gen2(T o) {     
    super(o);     
  }     
}     
     
// Demonstrate runtime type ID implications of generic class hierarchy.     
public class HierDemo3 {      
  public static void main(String args[]) {      
        
    // Create a Gen object for Integers.     
    Gen<Integer> iOb = new Gen<Integer>(88);     
     
    // Create a Gen2 object for Integers.     
    Gen2<Integer> iOb2 = new Gen2<Integer>(99);      
       
    // Create a Gen2 object for Strings.     
    Gen2<String> strOb2 = new Gen2<String>("Generics Test");      
     
    // See if iOb2 is some form of Gen2.    
    if(iOb2 instanceof Gen2<?>)      
      System.out.println("iOb2 is instance of Gen2");     
    
    // See if iOb2 is some form of Gen.    
    if(iOb2 instanceof Gen<?>)      
      System.out.println("iOb2 is instance of Gen");     
     
    System.out.println();     
     
    // See if strOb2 is a Gen2.    
    if(strOb2 instanceof Gen2<?>)      
      System.out.println("strOb is instance of Gen2");     
     
    // See if strOb2 is a Gen.    
    if(strOb2 instanceof Gen<?>)      
      System.out.println("strOb is instance of Gen");     
    
    System.out.println();     
     
    // See if iOb is an instance of Gen2, which its not.    
    if(iOb instanceof Gen2<?>)      
      System.out.println("iOb is instance of Gen2");     
     
    // See if iOb is an instance of Gen, which it is.    
    if(iOb instanceof Gen<?>)      
      System.out.println("iOb is instance of Gen");     
     
    // The following can't be compiled because     
    // generic type info does not exist at runtime.    
//    if(iOb2 instanceof Gen2<Integer>)      
//      System.out.println("iOb2 is instance of Gen2<Integer>");     
  }      
}