overriding

The generic entity, super class: @MappedSuperclass public abstract class GenericEntity { private Integer id; public Integer getId() {return id;} public void setId(Integer id) {this.id = id;} } The pojo: @Entity @Table(name = "POJO_ONE") @SequenceGenerator(name = "HB_SEQ_POJO_ONE", sequenceName = "SEQ_POJO_ONE", allocationSize = 1) public class PojoOne extends GenericEntity { @Id @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "HB_SEQ_POJO_ONE") @Column(name = "ID") @AttributeOverride(name = "id", column = @Column(name = "ID")) private Integer id; @Override public Integer getId(

How can I call the eat and drink method of the Animal class with the myAnimal instance in the code? public class Animal { public void eat() { System.out.println("Animal Eats"); } public void drink() { System.out.println("Animal Drinks"); } } public class Cat extends Animal { @Override public void eat() { System.out.println("Cat Eats"); } @Override public void drink() { System.out.println("Cat Drinks"); } public static void main(String[] args) { Cat myCat = new Cat(); myCat.eat(); myCat.drink(); Animal myAnimal = myCat; myAnimal.eat(); myAnimal.drink(); } } Output that I am getting: Cat Eats

I am trying to write a class library that can catch the windows messages to notify me if a device has been attached or removed. Normally, in a windows forms app I would just override the WndProc method but there is not WndProc method in this case. Is there another way I can get the messages? You'll need a window, there's no way around that. Here's a sample implementation. Implement an event handler for the DeviceChangeNotifier.DeviceNotify event to get notifications. Call the DeviceChangeNotifier.Start() method at the start of your program. Call DeviceChangeNotifier.Stop() at the end of your

Let's assume this scenario in Visual C++ 2010: #include <iostream> #include <conio.h> using namespace std; class Base { public: int b; void Display() { cout<<"Base: Non-virtual display."<<endl; }; virtual void vDisplay() { cout<<"Base: Virtual display."<<endl; }; }; class Derived : public Base { public: int d; void Display() { cout<<"Derived: Non-virtual display."<<endl; }; virtual void vDisplay() { cout<<"Derived: Virtual display."<<endl; }; }; int main() { Base ba; Derived de; ba.Display(); ba.vDisplay(); de.Display(); de.vDisplay(); _getch(); return 0; }; Theoretically, the output of this

After reading through References To Theme Attributes I am trying to reference the value of an attribute in the my custom theme that I have set. I am applying a user-defined style to a CheckedTextView <CheckedTextView android:id="@+id/contactInfo" style="@style/ListViewCheckedTextViewRowStyle" > </CheckedTextView> The user-defined style is defined as : <style name="ListViewCheckedTextViewRowStyle" parent="@style/ListViewRowStyle"> <item name="android:checkMark">?android:listChoiceIndicatorMultiple</item> </style> My theme I created is defined as : <style name="Theme.Yellowgreen" parent="android

There is a possible optimization I could apply to one of my methods, if I can determine that another method in the same class is not overridden. It is only a slight optimization, so reflection is out of the question. Should I just make a protected method that returns whether or not the method in question is overridden, such that a subclass can make it return true? I wouldn't do this. It violates encapsulation and changes the contract of what your class is supposed to do without implementers knowing about it. If you must do it, though, the best way is to invoke class.getMethod("myMethod")

Why does the compiler give an error message when you reduce the visibility of a method while overriding it in the subclass? Joachim Sauer Because every instance of the subclass still needs to be a valid instance of the base class (see Liskov substitution principle ). If the subclass suddenly has lost one property of the base class (namely a public method for example) then it would no longer be a valid substitute for the base class. Because if this was allowed, the following situation would be possible: Class Sub inherits from class Parent. Parent has a public method foo , Sub makes that method