Erap Estrada

Hey guys.

I've been out of the IT industry close to two years now and I'm having a hard time landing a job.

I'm taking an SCJP exam at the end of the month that I'm hoping it will help.

BUT, after that what's your advice on the next certfication should I take?

What are the skills that you feel are in demand now or at least in the near future.

Database? SCWD?

Thanks for the advice!

Henry Wong wrote:
But it comes with a price, since your method must work with any type, and you don't know the generic type (except to say that it extends container). How can you add anything? You can only add items that satisfies all possible types supported by your method, and that is only null.

Henry

But changing the above line to this compiles fine:

void addMugs(List<? super Mug> container)

It's still many possibilities right?

So you're saying that you can add an object to that original list object creation but not within this method?

What type or subtypes can you add inside this method?

You can read only?

The book says you can't add it in the line below. Why? Where can you add new object then?

Thanks for helping me out.

public class GenericSubtypeTest { public static void main(String[] args){ List<Mug> mugs = new ArrayList<Mug>(); mugs.add(new Mug()); mugs.add(new Mug()); GenericSubtypeTest gst = new GenericSubtypeTest(); gst.addMugs(mugs); } void addMugs(List<? extends Container> container){ container.add(new Mug()); // COMPILER ERROR HERE } } class Container { } class Mug extends Container{ } class Cup extends Container{ }

I'm playing around some code, and got this:
public static void main(String[] args){ Map labels = new HashMap(); labels.put("1", "Bio"); labels.put("2", "Ala"); labels.put("3", "Aaron"); labels.put("4", "Aaahh"); Set keys = labels.entrySet(); for(Object s : keys){ System.out.println(s); } }

The result is this:

3=Aaron
2=Ala
1=Bio
4=Aaahh

Why is this the result? Or it should vary? It doens't say in the API that it should return a sorted Set or something.

Thanks for the help.

First question, from Oracle site it says I don't need to buy a voucher. I can just register to prometrix, is that right?

Second question, how come Whizlabs is still selling a voucher for only USD250? Is this legit? Can I use this voucher here in Canada?

In the S&B Book in page 578, it says...

When solving searching and sorting questions, two big gotchas are:

1. ... [this part is clear]
2. Using a Comparator in either the sort or the search, but not both.

You need the same comparator that you use in sorting to search it right? So you need it for both transaction.

Can someone please clarify the sentences quoted?

Thank you in advance.

Great. Thanks guys for the clarification.

public class SearchObjArray { public static void main(String[] args){ String[] sa = {"one", "two", "three", "four"}; Arrays.sort(sa); for(String s:sa) System.out.print(s+ " "); System.out.println("\none = "+Arrays.binarySearch(sa, "one")); System.out.println("--- reverse ---"); ResortComparator rs = new ResortComparator(); Arrays.sort(sa, rs); for(String s : sa) System.out.print(s+ " "); System.out.println("\none = "+Arrays.binarySearch(sa, "one")); System.out.println("one = "+Arrays.binarySearch(sa, "one",rs)); } } class ResortComparator implements Comparator<String>{ public int compare(String a, String b){ return b.compareTo(a); } }

Results are:

four one three two
one = 1
--- reverse ---
two three one four
one = -1
one = 2


Why "-1"?

Great questions and great answers. Thanks a lot guys!

I noticed in Java 6 API that the interface "Set" extends another interface "Collection".

I just thought you can't extend an interface but should be IMPLEMENTED ONLY.

Can anyone clarify this java rule?

Thanks a lot!

Hi guys. I just wonder what's more effective in terms of review.

Let's say after reading a chapter and take the self-quiz (which you miserably failed) you realized that you missed some important concept.

Should you move on to the next chapter and review it later or go back again and re-read it?

Thanks!

Pattern p = Pattern.compile("0[xX]([0-9a-fA-F])+"); // line 1 Matcher m = p.matcher("12 0x 0x12 0xf 0xg"); while(m.find()){ System.out.print(m.start() + " "); }

The output for that code is 6 and 11. BUT if you put space between the closing parenthesis and the plus (+) sign in line 1 the output is just 11.

My question is, how critical this spaces in the exam? This can be really tricky.

Thanks!

String s = new String ("abc");

In this case, because we used the new keyword, Java will create a new String object in normal (nonpool) memory, and s will refer to it. In addition, the literal "abc" will be placed in the pool.

What's a nonpool memory? How come there are two object from the above line of code?

Thanks guys!

Hi Guys.

I'm reviewing for SCJP 6 Using Kathy and Berth Book.

Where can I find mock exams that's targeting ONLY the lessons learned in a certain chapter of the book?

Online, the mock exams are combination of every topic in the book but I'm still in chapter 3.

Thanks!