// abstract class    
public abstract class AbsClass<T1 extends Par1Class,T2 extends Par2Class> {
        // code 
    }
 
 
// parametrized imlementation class
public class RealClass extends AbsClass<ClassThatExtendsPar1,ClassThatExtendsPar2Class> {
   // code
}
 
// non-parametrized imlementation class
public class RealClass extends AbsClass {
   // code
}

在我的实现中,我必须指定NONE或ALL参数.有可能使第二个参数不是强制性的,像这样：

// abstract class    
public abstract class AbsClass<T1 extends Par1Class,T2 extends Par2Class : default Par2Class > {
        // code 
    }
 
// parametrized only mandatory imlementation class
public class RealClass extends AbsClass<ClassThatExtendsPar1> {
   // code
}