Wrap Up

To wrap up this part of the course, let's go back and 0:00 take a look at the list of methods the system.object provides. 0:03 As we've seen we can override most of these methods 0:07 with their own implementations. 0:09 We've seen how overwriting ToString can provide a better conversion 0:11 of objects to string. 0:15 The default implementation provided by system.object is 0:17 just to print the object's type name. 0:21 We've seen how we can redefine what it means for 0:23 two objects to be equal by overriding equals and get hash code. 0:26 There are a couple more methods in system.object, we haven't looked at yet. 0:31 Finalize is used by the memory management system, 0:35 also known as the garbage collector. 0:39 You see every time a new object is created, 0:41 it's stored some place in the computer's memory. 0:44 We may create lots and 0:47 lots of objects, eventually we don't need access to some of these objects any more. 0:48 We don't have any way to delete them from memory and free up that space for 0:54 other objects, so these objects can just sit in memory taking up space. 0:58 Periodically, .NET memory management system runs the garbage collector which 1:04 goes through the memory and 1:09 finds objects that aren't being used by the program anymore. 1:10 It removes them from the memory and frees up the space. 1:13 We're given the opportunity to run some final code 1:17 right before the object is removed, that's the purpose of the finalize method. 1:20 We can override the finalize method and write whatever code we want there. 1:26 Typically, finalize is used to close files and 1:30 clean up any other computer resources that the object may have been using. 1:33 Most of the time we don't need to think about the finalizer method. 1:37 Writing finalizer methods is something that is rare, 1:41 so we won't go into it right now. 1:44 The MemberwiseClone method is exactly what it sounds like. 1:46 It is used to create a copy of an object. 1:50 The method is protected so it's only accessible from within the subclass. 1:53 But it also can't be overridden by subclasses because it's not virtual, 1:57 this method is rarely used in practice. 2:02 So that's the system.object class. 2:05 In most cases, we don't interact with this class directly, 2:08 instead we use it indirectly through a subclass. 2:12 Because all classes inherit from system.object, 2:16 we can count on all objects having these methods. 2:19 This is just one more example of how polymorphism 2:23 with virtual methods is useful. 2:27 In the next part of this course, we'll learn about the final basic principle of 2:29 object oriented programming, abstraction. 2:33 We'll learn how C # supports this principle by 2:36 further extending the tree house defense game. 2:39