Sun Certified Java Programmer 310-065-Lesson 8-Assignments-Part 1

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Title: Sun Certified Java Programmer 310-065-Lesson 8-Assignments-Part 1

Duration: 15:30 min.

Summary: In this video, we move into assignments. Our exercises will cover scope, which is the lifetime of an object. Java Supports 4 basic variable scopes: Static variable, instance variable, local variable, and block variable. We will also talk about passing variables into methods, Arrays, and initialization blocks. Static initialization blocks run once, when the class is first loaded. Instance initialization blocks run every time a new instance is created. This video and the next will include discussions of garbage collection. Garbage collection is the way Java claims memory that is not reachable by the application.

Methodology of the development of example: Good coding standard and simplified design to prepare for the Java programmer certification exam CX-310-065.

Technology Used: Java - Core Concepts

Keywords: Sun Certified Java Programmer, Stack, Heap, Scope, Variable, Object, class, Assignment, Methods, reference, garbage collection, Array, initialization blocks, Boxing, Overloading.

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Matthew Casperson
The code for question 1 is:

class CardBoard {

Short story = 200;

CardBoard go(CardBoard cb) {

cb = null;

return cb;

}

public static void main(String[] args) {

CardBoard c1 = new cardBoard();

CardBoard c2 = new cardBoard();

CardBoard c3 = c1.go(c2);

c1 = null;

// do stuff

} }

When // do Stuff is reached, it is correct that 2 objects are eligible for GC, however it is not for the reasons described in the video.

The CardBoard object that was pointed to by c1 is eligible for GC, because c1 is set to null.

The Short object referenced by the CardBoard object referenced by c1 is also eligible for GC, because it's parent object is now no longer accessible (because c1 was set to null).

However, the variable c2 still points to an instance of the CardBoard class even after c1.go(c2) has returned. The video states that c2 will be set to null, which is incorrect. If you were to add the line of code

System.out.println(c2.story.toString());

before // do stuff, "200" would be printed to the console. This can only be the case of c2 still points to a CardBoard object.

[+1 year ago] Answer it

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Sun Certified Java Programmer 310-065-Lesson 8-Assignments-Part 1 | Java courses

In this video, we move into assignments. Our exercises will cover scope, which is the lifetime of an object.