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Why arraycopy() does not obey the lowerCamelCase convention? [duplicate]

While studying the standard Java library and its classes, i couldn't help noticing that some of those classes have methods that, in my opinion, have next to no relevance to those classes' cause.
The methods i'm talking about are, for example, Integer#getInteger, which retrieves a value of some "system property", or System#arraycopy, whose purpose is well-defined by its name.
Still, both of these methods seem kinda out of place, especially the first one, which for some reason binds working with system resources to a primitive type wrapper class.
From my current point of view, such method placement policy looks like a violation of a fundamental OOP design principle: that each class must be dedicated to solving its particular set of problems and not turn itself into a Swiss army knife.
But since i don't think that Java designers are idiots, i assume that there's some logic behind a decision to place those methods right where they are. So i'd be grateful if someone could explain what that logic really is.
Thanks!
Update
A few people have hinted at the fact that Java does have its illogical things that are simply remnants of a turbulent past. I reformulate my question then: why is Java so unwilling to mark its architectural flaws as deprecated, since it's not like that the existing deprecated features are likely to be discontinued in any observable future, and making things deprecated really helps refraining from using them in newly created code?

This is a good thing to wonder about. I know about more recent features (such as generics, lambda's etc) there are several blogs and posts on mailing lists that explain the choices made by the library makers. These are very interesting to read.
In your case I expect the answer isn't too exiting. The reason they were made is hard to tell. But both classes exist since JDK1.0. In those days the quality of programming in general (and also Java and OO in particular) was perhaps lower (meaning there were fewer common practices, library makers had to invent many paradigms themselves). Also there were other constraints in those times, such as Object creation being expensive.
Many of those awkwardly designed methods and classes now have a better alternative. (See Date and the package java.time)
The arraycopy you would expect to be added to the Arrays class, but unfortunately it is not there.
Ideally the original method would be deprecated for a while and then removed. Many libraries follow this strategy. Java however is very conservative about this and only deprecates things that really should not be used (such as Thread.stop(). I don't think a method has ever been removed in Java due to deprecation. This means it is fairly easy to upgrade your software to a newer version of Java, but it comes at the cost of leaving some clutter in the libraries.
The fact that java is so conservative about keeping the new JDK/JRE versions compatible with older source code and binaries is loved and hated. For your hobby project, or a small actively developed project upgrading to a new JVM that removes deprecated functions after a few years is not too difficult. But don't forget that many projects are not actively developed or the developers have a hard time making changes securely, for instance because they lack a proper regression test. In these projects changes in APIs cost a lot of time to comply to, and run the risk of introducing bugs.
Also libraries often try to support older versions of Java as well as newer version, they will have a problem doing so when methods have been deleted.

The Integer-example is probably just a design decision. If you want to implicitly interpret a property as Integer use java.lang.Integer. Otherwise you would have to provide a getter method for each java.lang-Type. Something like:
System.getPropertyAsBoolean(String)
System.getPropertyAsByte(String)
System.getPropertyAsInteger(String)
...
And for each data type, you'd require one additional method for the default:
- System.getPropertyAsBoolean(String, boolean)
- System.getPropertyAsByte(String, byte)
...
Since java.lang-Types already have some cast abilities (Integer.valueOf(String)), I am not too surprised to find a getProperty method here. Convenience in trade for breaking principles a tiny bit.
For the System.arraycopy, I guess it is an operation that depends on the operating system. You probably copy memory from one location to another in a very efficient way. If I would want to copy an array like that, I'd look for it in java.lang.System

"I assume that there's some logic behind a decision to place those
methods right where they are."
While that is often true, I have found that when somethings off, this assumption is typically where you are mislead.
A language is in constant development, from the day someone proposes a new language to the day it is antiquated. In between those extremes are some phases that the language, go through. Especially if someone is spending money on it and wants people to use it, a very peculiar phase often occurs, just before or after the first release:
The "we need this to work yesterday" phase.
This is where stuff like this happens, you have an almost complete language, but the programmers need to do something to to show what the language can do, or a specific application needs a feature that was not designed into the language.
So where do we add this feature?
- well, where it makes most sense to that particular programmer who's task it is to "make it work yesterday".
The logic may be that, this is where the function makes the most sense, since it doesn't belong anywhere else, and it doesn't deserve a class of its own. It could also be something like: so far, we have never done an array copy, without using system.. lets put arraycopy in there, and save everyone an extra include..
in the next generation of the language, people will not move the feature, since some experienced programmers will complain. So the feature may be duplicated, and found in a place where it makes more sense.
much later, it will be marked as deprecated, and deleted, if anyone cares to clean it up..

Groovy Migration for Java Developer [closed]

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Closed 11 years ago.
I've been a Java developer for several years now. Lately there's been quite the buzz over Groovy. I checked it out and it looks interesting and all, but I'm not seeing any inherent "wow factor" to it; meaning, I'm not seeing any intrinsic value to begin developing in it.
Now, I'm positive that I'm just not seeing the forest through the trees here. So, I ask the SO community at large: how would learning Groovy behoove any Java developer? What features/capabilities/etc. does it do (or do better) than plain ole' Java?
Things in the software world don't take off like wildfire without a reason. I'm sure Groovy has all sorts of nifty little (and big) capabilities that make it a must-know; I'm just not "getting" it. Thanks in advance.

In my opinion, some of the biggest adventages Groovy has over Java are:
terser code thanks to overloaded operators and simplified property access. Instead of writing
if (obj1.getBar().equals(obj2.getBaz())) {
obj3.setFoo("equal");
}
you can write
if (obj1.bar == obj2.baz) {
obj3.foo = "equal"
}
which I consider much more readable.
inline notation for Maps and Lists. Instead of
Map attributes = new HashMap();
attributes.put("color", "red");
attributes.put("width", 1);
you can write
def attributes = [color: "red", width: 1]
useful extensions to standard libraries. For example, you can read files and webpages like this:
def fileContents = new File('readme.txt').text
def pageContents = new URL('readme.txt').text
syntactic sugar for initializing properties - for example,
MyClass myObject = new MyClass();
myObject.setFoo("bar");
myObject.setBaz(23);
can be replaced by
def myObject = new MyClass(foo: "bar", baz: 23)
'safe' dereferencing - if (str != null) {return str.toUppercase();} else {return null;} becomes return str?.toUppercase()
Regular Expressions look nicer
Closures allow you to write code in 'functional' style, and make writing things like event listeners way easier

... since no one pitched in so far, I'd suggest looking at the Grooy mailing list. Similar questions pop up from time to time regarding Grails as well. Those are great communities of people who at some point or another faced the same type of questions.

I'll add another, since I don't see it explicitly mentioned.
For me, while terseness is nice on its own, it isn't the main point.
Whatever code you write, Java will always look like Java, and it will never read like the problem you're solving--it will read like Java, solving your problem.
I want the reverse: I want my code to read like the problem I'm solving, written in [insert language here].
Groovy is more expressive, more malleable than Java. It can look like what I'm trying to do. Canonical examples of this include internal DSLs. One I've used frequently is easyb, which is just Groovy code, but sounds like what I'm doing when I read it out loud. There are a bunch more examples, but easyb is an easy sell.
Also not mentioned are the AST transformations allowing cool compile-time tricks. You can play similar games in Java with things like AspectJ, but it's not as "baked in". Things like #Delegate, #Singleton, etc. are just plain handy.
For me, a language needs to be malleable, deformable, flexible: Java is not. Java has an impoverished model of abstraction making it frustrating to work with--the amount of extra work, writ both small and large throughout the language, is mind-boggling at times.

You're kinda late to the party. Groovy saw its dawn about 4 years ago when people fed up with Java's ridiculous verboseness were ready to give up performance in the sake of code reduction and Groovy was providing them with exactly that in a very familiar syntax. But now that it's been there for a while it gets dragged by its past as much as every language does and some not best design decisions are there to stay as much as I'm pretty sure are its performance issues. This basically was the reason of emergence of Groovy++, the whole existance of which suggests that there are some problems with its predecessor. And in fact Groovy++ addresses a lot of issues of its predecessor, but it also has its own problems: the main one being that it's basically driven only by the devotion of a one man - Alex Tkachman that is, - and no funding, so you should see all the risks involved.
Nowadays that more and more strong rivals appear (Kotlin, Ceylon) it becomes obvious to me that Groovy has already passed even its zenith - even its core team is trembling (you should see their discussions on Grumpy mode). This was the reason for me to start gradually leaving this technology in preference to Scala and to look forward to forthcoming Kotlin which both are great projects but take some effort for a "Java mind" to switch to, but are definitely worth it.
Updates due to hypercritical response:
Design mistakes:
Restricting syntax for Java paste-in compatibility, while a seemingly neat feature in practice turned out to be not used at all, 'cuz migrating Java code to Groovy is generally a bad idea for the same performance reasons. But this resulted in inheritance of some Java's ridiculousness like not being able to define a variable of the name used in the outer context
While keeping some of Java's bad practices they got rid of some of its good features too, like code blocks demarked with curly braces in preference to closures. The issue solved much neater in Scala
Dynamic typing was mainly chosen because decent type inferring was hard to realize - that was basically the reason for Groovy's creator to later state that he would have never bothered creating it if he knew about Scala back then.
Googling for "groovy performance" will give you enough results. Here is one: http://stronglytypedblog.blogspot.com/2010/02/java-vs-scala-vs-groovy-vs-groovy.html
I never stated that Groovy++ is the same project as core Groovy.
I would like you to know that I once was a huge fan of Groovy and was developing in it exclusively for 2 straight years. Moving on to a new language was a very hard step for me to take. But since I know Groovy's every corner, I know its core team and its tendencies you should understand that I know what I'm doing when I'm recommending not to consider Groovy as an alternative to Java.

Is it compulsory to learn about Data Structures if you want to be a Java/C++ programmer? [closed]

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Closed 10 years ago.
So do I really need to learn about them ? Isn't there an interesting way to learn about stacks, linked lists, heaps, etc ? I found it a boring subject.
**While posting this question it showed some warning. Am I not allowed to post such a question ? Admins please clarify and I will delete it :/
Warning :: The question you're asking appears subjective and is likely to be closed.
okay..I get it
So what is THE best way to learn them ? What book do I refer ? What website ?

It's compulsory to learn about data structures if you want to be a programmer. Data structures are your bread-and-butter - if you don't understand things like the behavior, uses, and run-time complexity ('big-O') of at least the basic structures (arrays, linked lists, stacks, queues, trees (binary / n-ary, self-balancing varietes), hash-tables, heaps, graphs) and the algorithms that run on them (insert / locate / delete), you won't know which is appropriate to use under what circumstances.
Every trade has its tools; these are ours. Data structures are the most basic underpinnings of almost any algorithm that you're going to learn. Unless you want to be a cargo cult programmer, you need to understand how they work.
Whether or not there are interesting ways to learn about them is a separate question entirely... :)

I would go even so far as to say that most of programming revolves around manipulating data structures, it is the foundation of computing after all: you get some data, you process it, you possibly give output. All the data usually reside in data structures and choosing inappropriate structures will have the bigger impact the bigger the project.

As you get more experience you will find that algorithms and datastructures are invaluable to your day-to-day development, and actually pretty interesting.
By learning about them now you will learn:
Which data structure is appropriate for which context, i.e. when to use a single-linked list, when to use a stack, when to use a queue, when to use a tree
Which algorithms are appropriate for which purpose, such as tree depth-first search or breadth-first search.
Space and time complexity of algorithms, for example why is a quicksort sometimes the best solution, and sometimes heapsort.
Overall it'll teach you the beginnings and fundamentals of computer science, even if you never have to implement a stack again you'll know the kind of thought and consideration that goes into it. If you then ever have to implement your OWN data structure (and chances are you will, quite often), you will know what to do and what not to do.

If you want to be a successful programmer, data structure is a must. How will you program if you don't know data structures and algorithms?

Whether you like it or not, all programming is built around data structures. You may never have to write one, but you will have to choose which one to use many times. It is not really a requirement to programming in general, but if you want to excel in the field, understanding of the basics is a must.
Anyone can build a shed without knowledge of materials or construction techniques. You can even work in a house placing bricks and mortar under the orders of someone else, but if you want to build a house yourself, you do need to understand materials and techniques.
Data structures are the programming materials. Algorithms are techniques. Will you use data structures? You will use the simplest ones in a daily basis, each so often you will need to solve a problem where an specific data structure is required, and while you may manage not to build your own bricks, you will need to understand whether you need bricks or a concrete wall for your purposes.

If you want some evidence for the importance of data structures, take a look at the Google hiring process. Whatever you think about Google as a company, there is no denying that they have some very good people working for them. Their interview process is setup to determine the candidates knowledge of data structures and algorithms. Because when it comes down to it, that is what is at the core of programming, no matter what language you are working in or what domain you are programming for.
If you are planning a career as a professional programmer, you need to know the fundamentals, not just how to crank out code that "works". Otherwise, your just playing.

Is it compulsory to learn about arithmetic to be an engineer?

If you take the attitude of "is it compulsory" with regards to any of the building blocks of programming languages, you're probably not cut out to be a coder. Regardless of "compulsory" or not, you should always be looking for new concepts to learn and seeing if it'll improve your coding style/standard.
But in answer to your question: yes.

I'd say it's compulsory at some point in your development to have a firm grasp. I'm not necessarily sure the standard Data Structures course is the best way to learn. Sometimes, the best way to learn them is "I have problem X. For some reason, it's taking my algorithm a long time to solve X. How can I make this faster?"
One book I'd highly recommend is Programming Pearls. It has some really good analyses, backed by a lot of examples of where the real-world motivations for the solutions came from. It presents the problems in an interesting manner, and never teaches by giving you a laundry list of data structures.

Yes 99% of books on Data Structures are boring and exercises contrived. They feel like they are just making up problems that server no practical purpose :(
This book is the one exception to the rule I've come across. You will have a naive but working RPG game by the end of the book:
Data Structures for Game Programmers
Read the above book and you will solve your chicken and egg problem and see you really can't do much without data structures after all.

Well, this may sound a little awkward but I wouldn't say it is COMPULSORY to learn Data Structures to be a - regular- developer. Seriously! Of courser if you study then hard it will give you a lot of insights and knowledge on several programming aspects and that's always good. But compulsory ... well, I think it is just too much. VERY GOOD would be enough.
Let me explain why. It is not that often, for today, to write Data Structures code because - let's face it - it would be RE-writing, RE-inventing what we already know for so many years! What I would say it is COMPULSORY is to study just the general theory of them and the APIs/libraries that are already commonly in use (and tested and optimized) like the Collections API in Java. You must know by heart the differences between a List and a Set (in Java for instance) and their capabilities and proper usage but you don't need to know exactly HOW they are implemented - checking every private method and attribute - to deal with most common, day to day, coding problems. You will do just fine without all the "guts" of Data Structures for the general stuff. We face different challenges now.
But don't get me wrong - neither think I am crazy or naive! Off course there are situations that you will need to implement yourself some sort of custom data structure (maybe your own BalancedBinaryTreeMap!). You got to be prepared for everything.
I am just arguing about being compulsory or not. Again, I don't think is compulsory but it is indeed very good.
Cheers.

I suppose you could learn programming without learning a whole lot about data structures or algorithms. To make an equivalent example, think of it like if a carpenter knew how to build things, but didn't know about measurements and such. Would he be able to get a career in carpentry? Possibly, but let's say he needed to know the exact material he would need to complete a project. He'd probably get fired because he doesn't know what sort of material or measurements to use.
So with data structures and algorithms, you can say it's the ability to give exact measurements of an application and knowing what sort of performance you'll get out it.

Like a musician learning scales, data structures are part of the tools of the software trade. Sure you can work as a programmer without the knowledge but you're handicapping yourself. If I'm interviewing two people for a position and one of them understands and uses structures and the other can't even explain what a stack is, my choice is pretty clear.
If you want to be judged to be a competent, employable programmer, you need to learn your craft.

Is it compulsory to learn them?
No, you can program without them, just as it's not compulsory to break your code into functions.
That being said, if you want to be an effective programmer that can write at least decent code without getting your car egged by your coworkers, you want to at least be able to make a decent selection of library classes.
Every programmer should understand the tradeoff between a LinkedList and an Array, or why binary searches and binary trees are useful for sorted data. This isn't just about performance - it's about correctness too since you can't just put anything into a tree set.
Does it mean that you need to know how to implement your own AVL tree, build super-smart data structures, etc.? Not necessarily. It's a matter of how much you want to know what's going on "beneath the hood" and whether your tasks necessitate it.
I'm not a big fan of deep data structure and algorithms questions in interviews because the vast majority of developers don't need to implement these things, just to use library stuff. I prefer to ask job related questions in interviews. However, accept that if you don't learn those things you would face a tougher battle to get other jobs.

It should be, yes...

No body should force you to learn anything you don't want to learn.
If you're the type of person that is compelled to be the best that he/she can be at what he/she does, and you love what you do for a living, you'll learn everything there is to know on your own accord.
#happysoul: You should ask yourself WHY learning data structures bore you. Also, it would help if you also identify what DOESN'T bore you.
If you at least love to learn about algorithms, I'm sure we can all suggest a perfect marriage of the two that would be exciting to learn!
My recommendation for best algorithm/data structure combo for the most fun learning experience: graphs.

How easily customizable are SAP industry-specific solutions?

First of all, I have a very superficial knowledge of SAP. According to my understanding, they provide a number of industry specific solutions. The concept seems very interesting and I work on something similar for banking industry. The biggest challenge we face is how to adapt our products for different clients. Many concepts are quite similar across enterprises, but there are always some client-specific requirements that have to be resolved through configuration and customization. Often this requires reimplementing and developing customer specific features.
I wonder how efficient in this sense SAP products are. How much effort has to be spent in order to adapt the product so it satisfies specific customer needs? What are the mechanisms used (configuration, programming etc)? How would this compare to developing custom solution from scratch? Are they capable of leveraging and promoting best practices?

Disclaimer: I'm talking about the ABAP-based part of SAP software only.
Disclaimer 2, ref PATRYs response: HR is quite a bit different from the rest of the SAP/ABAP world. I do feel rather competent as a general-purpose ABAP developer, but HR programming is so far off my personal beacon that I've never even tried to understand what they're doing there. %-|
According to my understanding, they provide a number of industry specific solutions.
They do - but be careful when comparing your own programs to these solutions. For example, IS-H (SAP for Healthcare) started off as an extension of the SD (Sales & Distribution) system, but has become very much more since then. While you could technically use all of the techniques they use for their IS, you really should ask a competent technical consultant before you do - there are an awful lot of pits to avoid.
The concept seems very interesting and I work on something similar for banking industry.
Note that a SAP for Banking IS already exists. See here for the documentation.
The biggest challenge we face is how to adapt our products for different clients.
I'd rather rephrase this as "The biggest challenge is to know where the product is likely to be adapted and to structurally prepare the product for adaption." The adaption techniques are well researched and easily employed once you know where the customer is likely to deviate from your idea of the perfect solution.
How much effort has to be spent in
order to adapt the product so it
satisfies specific customer needs?
That obviously depends on the deviation of the customer's needs from the standard path - but that won't help you. With a SAP-based system, you always have three choices. You can try to customize the system within its limits. Customizing basically means tweaking settings (think configuration tables, tens of thousands of them) and adding stuff (program fragments, forms, ...) in places that are intended to do so. Technology - see below.
Sometimes customizing isn't enough - you can develop things additionally. A very frequent requirement is some additional reporting tool. With the SAP system, you get the entire development environment delivered - the very same tools that all the standard applications were written with. Your programs can peacefully coexist with the standard programs and even use common routines and data. Of course you can really screw things up, but show me a real programming environment where you can't.
The third option is to modify the standard implementations. Modifications are like a really sharp two-edged kitchen knife - you might be able to cook really cool things in half of the time required by others, but you might hurt yourself really badly if you don't know what you're doing. Even if you don't really intend to modify the standard programs, it's very comforting to know that you could and that you have full access to the coding.
(Note that this is about the application programs only - you have no chance whatsoever to tweak the kernel, but fortunately, that's rarely necessary.)
What are the mechanisms used (configuration, programming etc)?
Configurations is mostly about configuration tables with more or less sophisticated dialog applications. For the programming part of customizing, there's the extension framework - see http://help.sap.com/saphelp_nw70ehp1/helpdata/en/35/f9934257a5c86ae10000000a155106/frameset.htm for details. It's basically a controlled version of dependency injection. As a solution developer, you have to anticipate the extension points, define the interface that has to be implemented by the customer code and then embed the call in your code. As a project developer, you have to create an implementation that adheres to the interface and activate it. The basic runtime system takes care of glueing the two programs together, you don't have to worry about that.
How would this compare to developing custom solution from scratch?
IMHO this depends on how much of the solution is the same for all customers and how much of it has to be adapted. It's really hard to be more specific without knowing more about what you want to do.

I can only speak for the Human Resource component, but this is a component where there is a lot of difference between customers, based on a common need.
First, most of the time you set the value for a group, and then associate the object (person, location...) with a group depending on one or two values. This is akin to an indirection, and allow for great flexibility, as you can change the association for a given location without changing the others. in a few case, there is a 3 level indirection...
Second, there is a lot of customization that is nearly programming. Payroll or administrative operations are first class example of this. In the later cas, you get a table with the operation (hiring for example), the event (creation, modification...) a code for the action (I for test, F to call a function, O for a standard operation) and a text field describing the parameters of a function ("C P0001, begda, endda" to create a structure P001 with default values).
Third, you can also use such a table to indicate a function or class (ABAP-OO), that will be dynamically called. You get a developer to create this function or class, and then indicate this in the table. This is a method to replace a functionality by another one, or extend it. This is used extensively in the ESS/MSS.
Last, there is also extension point or file that you can modify. this is nearly the same as the previous one, except that you don't need to indicate the change : the file is always used (ZXPADU01/02 for HR modification of infotype)
hope this help
Guillaume PATRY

How to revise java? [closed]

As it currently stands, this question is not a good fit for our Q&A format. We expect answers to be supported by facts, references, or expertise, but this question will likely solicit debate, arguments, polling, or extended discussion. If you feel that this question can be improved and possibly reopened, visit the help center for guidance.
Closed 10 years ago.
Ok so this isn't 100% programming question, for which I'm really sorry, but still this is the best place I know to ask it.
In ~2weeks time I'll have a job interview, first they'll make me take a test from Java and I was wondering what's the best way to prepare for it? I bet it will be something similar to SCJP (but probably much easier), are there any (short) books, tutorials that are worth reading? I did order the SCJP book by Sierra/Bates but I won't be able to read it before the test.
Don't get me wrong I do have experience with Java etc. but I really want to get the job so I want to go there well prepared.
Also marry Xmas to everyone, no matter what religion you are.

Don't get me wrong I do have
experience with Java etc. but I really
want to get the job so I want to go
there well prepared.
If you have enough experience don't worry about the test. Don't try to impress your next boss with an awesome test that does not reflect your current knowledge. Read Joel's posts about interviewing:
The second worst kind of interviewer
is the Quiz Show Interviewer. This is
the kind of person who thinks that
smart means “knows a lot of facts.”
They just ask a bunch of trivia
questions about programming and give
points for correct answers. Just for
fun, here is the worst interview
question on Earth: “What’s the
difference between varchar and
varchar2 in Oracle 8i?” This is a
terrible question. There is no
possible, imaginable correlation
between people that know that
particular piece of trivia and people
that you want to hire. Who cares what
the difference is? You can find out
online in about fifteen seconds!
Remember, smart does not mean “knows
the answer to trivia questions.”
Anyway, software teams want to hire
people with aptitude, not a particular
skill set. Any skill set that people
can bring to the job will be
technologically obsolete in a couple
of years, anyway, so it’s better to
hire people that are going to be able
to learn any new technology rather
than people who happen to know how to
make JDBC talk to a MySQL database
right this minute.
quoted from "The Guerrilla Guide to Interviewing (version 3.0)" by Joel Spolsky
If you need to impress someone to get the job, may be that's not a good place to work...

I recommend you pick up Effective Java, 2nd Edition by Joshua Bloch and read it cover to cover. It details several "best practices" for Java and will have you walking into the interview knowing for example things like:
when to use Static Factory Methods
when to use the Builder Pattern
what a Singleton is and how to enforce it
how to prevent instantiation of a class
why to avoid finalizers
the general contract for overriding equals and hashcode
to use accessor methods instead of public fields
to prefer lists to arrays
to favor generic types
to use enums instead of int constants
to return empty collections or arrays instead of null
to prefer for-each loops over traditional for loops
to avoid float and double if exact values are needed
beware of performance loss when doing string concatenation
refer to objects by their interfaces
Not to mention the other 40 or so topics that I can't remember off the top of my head. If you're able to talk about these topics and demonstrate an understanding, then there's no reason you shouldn't be in the running for the position since learning this material will already put you in the top 10 percentile of Java developers.

I have a little book with "Exam Cram" in its title. The emphasis is on "little;" you can read through it in a single evening. It describes in prose all the important features of Java, it contains tables of quick facts that will be essential, and it covers, briefly, all of the SCJP exam.
For the less than eidetic, it gives hints on how to write yourself a crib sheet from memory once the test starts (meaning you can carry a bit of what you need to know in short-term memory). There are also some tips on pitfalls and such. Finally, and perhaps most importantly, there is at least one practice exam in it (haven't looked at it in a while) and a bunch of drill questions.
Alas, from what I see at Amazon, the book I recommended only covers Java 2: http://www.amazon.com/Java-Exam-Cram-310-025/dp/1576102912 Still, there are bound to be similar, more timely books.
This one: http://www.amazon.com/SCJP-Certified-Programmer-Java-310-065/dp/0071591060/ref=sr_1_1?ie=UTF8&s=books&qid=1261601183&sr=1-1 by Kathy Sierra is similar and about Java 6.
Some people would (and in fact did) recommend buying a general purpose Java book. Ideally, all you should have to do is learn "all of Java" and then you'd be ready for the exam. But this is not a winning strategy!
related anecdote
The first time I took my driver's test with the DMV, I had a long wait and quickly skimmed through a little info booklet they provided. I easily scored 100.
I later had to take the test again. Knowing the test was laughably easy, I spurned the booklet and failed the theoretical test. The booklet didn't contain anything I didn't already know: But being by the same people who administer the test, it contained the same wording, it had similar situations from the test, it emphasized similar topics and situations. In a few minutes, it could easily make the difference between passing and failing.
Conclusion
Same approach with these "prepare for test XXX" books. It's a racket, but the special-purpose prep books work better at preparing you for the test than general knowledge (or general knowledge books) do.

May be you should read Eckel's Thinking in Java. In this book many specific java features are considered.

I would rather prepare my self to explain what I already know about java and how much I would like to work for that company.
While the programming knowledge is essential, I don't think you can improve much further in two weeks.
Better would be for you to prepare to answer, why do you want to work there, why should they hire you. etc.

My recommendation is HeadFirst Java to brush up on anything you may have some issues on. The SCJP is something that they may make you take upon hiring within 6 months for example, however I have never heard of a company making someone take a proctored test at an interview. Hope this helps.

Write something small but useful in Java, in whatever environment they're going to be using (applets, JSP, desktop...). That way you won't freeze trying to remember how to do e.g. console output.

If possible, show them some Java code you've obviously written and that you're proud of.

Brush up or learn the following :
Simple concepts e.g. static keyword, importance of equals and hashCode, etc.
How generics in java work?
How threading works, deadlock, race conditions, etc.
How java deals with memory. Can garbage collection be enforced?
Basics of OOP.
Basics of String, StringBuffer, StringBuilder, RuntimeException, etc.
Design patterns, e.g. singleton, visitor, etc.

If you want to know the language well then The Really Big Index will be invaluable. It's a huge list and you'd struggle to read it straight though but for a reference it's fantastic. Read it along with a set book like Thinking in Java or the SCJP book you've already ordered and you'll be absolutely fine.