Summary of JDK1.5 Language Changes

An anonymous reader writes "Over at java.sun.com, there's an informative article about the new features in JDK1.5. Some of the changes like generics are nice and should make some things easier. Some of the enhancements to me are purely sugar, like enumerators. When it comes down to it, once the code is compiled, it's the same. The thing I hope is, some of this new syntactic sugar doesn't result in more obfuscated code. Unlike some people, I feel using programming shorthand leads to increased maintenance. This is especially true when you have to debug a complex application."

Comments

enumerators

[billnapier]

enumerators are much better than just plain ints. Even though they may compile to the same thing, the compiler can do a little more checking on the enumerators, since it know the valid ranges for the enumerator so you don't have to explicitly check the range. You do check to make sure you get passed a valid value for all your int-as-enumerators? Don't you?

Re:enumerators

[customiser]

It's good to see enumerators formally supported, but you were not really _forced_ to use plain ints up to now. It is just some sort of an anti-pattern, which everybody seems to be using happily.

The type-safe enum pattern shows the correct way of handling enumerations. And you can the Jakarta Commons Lang library to make it a bit easier.

Re:enumerators

[iabervon]

They're actually objects (you can put them in collections, for instance), they can have fields, methods, and constructors, etc. It's just that the compiler takes care of creating the instances and all, plus you can use them in swtch statements because the compiler knows they're enumerated.

Evil thought: you could get relatively nice-looking static instances with methods if you combined enums with anonymous inner classes...

Re:enumerators

[ProfKyne]

I don't use ints for my enumerations anymore after reading Josh Bloch's Effective Java. The type-safe enum pattern he recommends is fantastic.

For those not sure exactly how it works, you simply create a class to represent an instance of the enum, and you make the constructor private so that no one can create their own instances. Then you just provide a public static instance of the class for each enum.

I used this pattern simply to achieve its intended effect of providing an enumeration, and then later found that by adding methods to the class, I could even give behaviors to the enumeration instances! Try doing that with an int. This was far more elegant than creating a giant "if" statement and performing conditional logic to test the value of the enumeration, because I simply used a polymorphic method call.

An example:

public class SenseEnumeration {
// the action associated with this enumeration
private java.lang.reflect.Method sense;

private SenseEnumeration(Method m) {
this.sense= m;
}

// assuming we've already created some
// Method instances to use here
public static SenseEnumeration TASTE
= new SenseEnumeration(myTasteMethod);
public static SenseEnumeration HEAR
= new SenseEnumeration(myHearMethod);
public static SenseEnumeration SMELL
= new SenseEnumeration(mySmellMethod);

...etc...

public Method getSenseMethod() { return this.sense; }
public void invokeSenseMethod(Object target) {
sense.invoke(target, null);
}
}

You get the main idea. No, not as fast as an int, but far more powerful.

Re:enumerators

[slagdogg]

This is a fine alternative ... but cumbersome, and indeed once you add the toString() methods and other such niceties, it's approaching messy. The fact that a single statement now can offer all of these features is outstanding.

It's nice to see Java stealing something from C# for once ;)

Re:enumerators

[revscat]

The article makes no claim about the typesafe enum pattern being broken, it just points out that you have to be careful if you use it and implement Serialzable. This is something that Bloch specifically addresses in Effective Java, and does not mean that the entire pattern should be scrapped. You just have to be aware of potential problems.

Re:enumerators

[billnapier]

That's what we've been using but my fingers get tired from typing all that extra crap in...

Re:enumerators

[bnenning]

By making them objects you have to worry about the compiler creating a lot of extra objects behind your back especially in tight highly used loops.

I would think they'd have to be like singletons, with the compiler creating exactly one instance of each enum value.

Re:enumerators

[Mindbridge]

Metadata has been supported by the Java VM since the beginning, and JSR 40 (the metadata stuff in the language) has been around since 1999. It is _very_ doubtful that Java got this from C#. I will grant you that it probably forced issues a bit, though :)

Re:enumerators

[Mindbridge]

Using the switch statement automatically means the programmer has slept through the OO class.
You simply do not need to use switch when you have polymorphism, which is a much more powerful mechanism and allows for much nicer scalable, maintainable, and readable code. Of course, this assumes that one has an understanding of OO.

If there is a problem with safe enums, it is with serialization and deserialization. There are a number of solutions available for that, however. Personally, I feel that those should have gotten in the Java libraries, not enums in the language, but oh well.
available such as , something that the safe enum provides, unlike the enumerations.

Re:enumerators

[iabervon]

The instances are created when the class is loaded, and there's only one copy of each value. It's essentially like you're using int constants, except they're pointer constants instead, so you can dereference them to get more information than just equality. It's essentially the same as

public class Season {
static public final Season spring = new Season();
static public final Season summer = new Season();
static public final Season fall = new Season();
static public final Season winter = new Season();

private Season() { }
};

Except it's only one line, there are useful additional methods (like a toString), and you can use it in a switch statement.

Re:enumerators

[spells]

Polymorphism is a single tool in the belt and doesn't replace switch statements.
Although I agree every instance of a switch statement can probably be implemented with polymorphismc some times you will end up with a worse design using polymorphic solutions that haven't placed enough emphasis on encapsulation and connascence. Options are good.

Generics

[boxhead609]

I think Generics is going to be a really nice long awaited feature. I am wondering if this type of change is going to require a modification to the bytecode specification. If that is the case, then new code bytecodes will not work with older bytecodes. Does anyone think that Sun can pull this feature off without a change to the bytecode spec? Would this be major compiler change?

Re:Generics

[gray peter]

Agreed that it's a great feature. I use collections all the time and not only is it time consuming to keep casting (especially when you write out long class names like I do...) I'd say a huge % of my runtime errors are from bad casting. I'm definitely looking forward to this. As far as the bytecode specs go, I don't see that this will cause much change at all. The compiler should do the same thing it's always done.

Re:Generics

[gray peter]

Read the article :-)

Re:Generics

[blamanj]

No bytecode changes are required. There have been "test" implementations out since Java 1.2. You can get the current 1.3 release at
http://developer.java.sun.com/developer/earlyAcc es s/adding_generics/

Re:Generics

[justins98]

I don't think it will require a bytecode change. I don't know the details of how it works, but my guess is that the compiler will simply insert the casts for you. For example, when you say:

List<Foo> list = new ArrayList<Foo>();
list.add( myFoo );
Foo otherFoo = list.get( 0 );

The compiler will interpret the second and third lines as if they said:

list.add( (Foo)myFoo );
Foo otherFoo = (Foo)list.get( 0 );

It's a pretty elegant way to incorporate type-safe generics without imposing any changes on the VM. I think the compiler changes would be relatively easy to implement -- nothing more than inserting casts at the appropriate places.

Re:Generics

[CognitivelyDistorted]

Pretty close. For "list.add(myFoo)", it won't add a cast, because the type checker verifies that myFoo is-a Foo. The compiler will also add "bridge methods" for classes that implement a parameterized interface:

class Byte implements Comparable<Byte> {
...
public int compareTo(Byte obj) {
return this.value - obj.value);
}
}

The method compareTo is supposed to override the method in Comparable, which takes an object. So they create a bridge method that overrides it normally:

class Byte implements Comparable<Byte> {
...
public int compareTo(Byte obj) {
return this.value - obj.value);
}
public int compareTo(Object obj) {
return this.compareTo((Byte) obj);
}
}

Re:Looking to Get Back into Java

[stevenknight]

check out eclipse -- a very sweet java IDE.
http://www.eclipse.org/

Programming shortcuts

[GGardner]

I feel using programming shorthand leads to increased maintenance

I agree. This is why I never create my own functions or methods. Evey program should be just one big function.

Re:Programming shortcuts

[NReitzel]

During my time at telco, development costs were always a fraction of maintenance costs. Producing write-only code may be cute, and may cut back on other people using it, but it also cuts back on your own people being able to maintain it.

Oh, do I agree, in boldface.

Re:Programming shortcuts

[eGabriel]

It's true that wading through 20 different ways of doing the same thing in one program can really be maddening, but within reason some of these shortcuts should exist, and should have from the beginning.

Every language has idioms, and a programmer should use those idioms in preference to other allowable ways to do things unless they have a good reason. It's all just part of good style.

Re:Programming shortcuts

[radish]

Of course maintenance costs more than development, that's a given. But the thing which reduces maintenance costs is easy to read and understand code, coupled with good documentation.

The ultimate removal of "syntatic sugar" would take you down to raw machine code. I do not believe that would be easier to maintain than Java, or pretty much any higher level language. The aim of syntatic constructs is (or should be) to make it easier for the developer to express the algorithm clearly. It's not about saving typing (unless we're talking perl) and not about being smart for the sake of it, it's about making it easier to read and understand.

Re:Programming shortcuts

[DunbarTheInept]

The problem is that some syntatic sugar doesn't actually increase readability. Consider operator overloading. If your language has that, you can never again know what on earth is going on when you see x = y + z, unless you are aware of every operator overload which was used. Let's say y is a char* and z is an integer. Normally then the expression (y+z) would mean in C++ "a char pointer which points at the character at index 'z' of the string stored in y." But with operator overloading in the language, you can never be too sure. Maybe somewhere in the code the programmer thought it would be a good idea to say that char* plus int really means "convert the string to integer with atoi(), then add the integer second argument to it, then convert back to string form and return that."

Re:Programming shortcuts

[dasmegabyte]

"Shortcuts" are not the problem. Stupidity is the problem. A good programmer, or at least a kind programmer, uses "shortcuts" so that somebody else can figure out what's going on without having to everything about an object.

Enumerated types will save your ass the first time you change databases or some project manager adds a new "status level" in between DONE and FINISHED. They are much faster than using internalized strings, which is how I had been testing for this crap. Remember, once they hit the object code they're just constants anyway...

Foreach was easily the coolest thing about C# when I started using it, indexers were the second, and the code they create is FAR more maintainable than for(Object o = someList.FirstItem(); o != someList.LastItem(); o = someList.NextItem()){ ...}.

Automagic "boxing" is a beautiful thing for newbie coders...I have had to teach so many the difference between a Byte and a byte that it isn't funny. I intend to use it, too...we pass in and out of the classes for char, int, byte, bool etc so often it makes sense to have the compiler/VM do our dirty work for us.

And generics...well, they look real queer in Java, where we've never used the syntax before. But they will save our behinds on reuse! Besides no doubt being faster, it will make more sense when typing collections of inherited objects. We have a BaseRecord class. We have an optimized BaseRecordColl class, usually full of different types of ChildRecord classes. If we can write the one collection class, and not have to explicitly cast each child op, it will save time, space, and hassle...and avoid calling the superclass methods of uncast subclasses!

Metadata is the only ingredient here that seems like it could cause trouble, and if it does it will be because people are using it wrong. Java is not a language that inlines...that's the whole idea of the JIT...and with today's cut and paste GUI IDEs, there's no need for programmers to use the lazy C declarations of the past. If people start doing so because it's neat, just nip it in the bud. Find/Replace when the code hits your desk. Eventually they'll get the hint.

Agreed..

[MilesParker]

..Thought C# has some nice innovations, one of my big problems with it is that so many of its new 'features' are so much syntactic sugar. One of the big things I appreciate about Java is that there is typically onyl one right way to do something; a big change from C++ for example. Plus, modern IDEs like IntelliJ make it very easy to construct iterators and such [Ctrl-j itar..] That said, I don't think that the majority of the Java improvements are really sytactic sugar; things like generics will be very positve improvements. And its very important that Sun keeps up these improvements -- as long as they continue to be well thought out. Ideally we will continue to have a fairly state-of-the art language without any fluff.

Re:Agreed..

[DunbarTheInept]

I'd say that "++x" is actually the "best" way because it puts things in verb-noun order, which I'm used to as an English speaker. "x++" is noun-verb, which feels strange to me. "++x" reads as "increment X", while "x++" reads as "x. increment it".

(Just goes to show there will be differences of opinion and no such thing as "the" right way. Here's another example:

if( x == 5 ) { do something }
versus
if( 5 == x ) { do something }

Some prefer the second way because it puts the term which cannot be a valid lvalue on the left side, thus if you make the common typo of "=" instead of "==", you will get a compile error from it, which wold not happen for x = 5. But, it looks very odd to write it 'backward' like that, so some say the readability of doing it the 'dangerous' way makes it worth doing it that way.

There is no such thing as "the" best way, not even in Java.

Re:Agreed..

[dhovis]

Actually, i believe that in Java

if(x = 5)

will throw a compiler error because (x = 5) does not resolve to boolean.

That is something I like about Java, it doesn't allow you to do stupid things like that. There is no reason to do an asignment in an if() statement.

So basically C# minus generics

[earache]

The metadata, auto-boxing, enhanced iteration looks like catch up with C#'s attributes, foreach, etc.

Where are true properties though?

Re:Looking to Get Back into Java

[gray peter]

The language I could pop right back into, but could use some advice on good/affordable IDE.

http://www.xemacs.org
what more do you need? ;-)

If you want a *real* IDE, I'd check out IntelliJ's Idea product. It's a few hundred $$$. Lots of folks like Netbeans and IBM's Eclipse as well (sorry, no url to eclipse, but I'm sure you can find it). The latter 2 are opensource.

Re:Looking to Get Back into Java

[Schezar]

Eclipse is "the awesome." It's feature-filled and relatively easy to use. Being free is a nice plus, too.

My roommate told me about it, and once I started using it I never looked back.

programming shorthand

[nother_nix_hacker]

I feel using programming shorthand leads to increased maintenance

My code was hard to write to it should be hard to read. :)

Much, much more than syntactic sugar

[jameson]

Hi,

FYI: Generics are _much_ more than mere syntactic sugar (as are enumerators, a weak form of algebraic datatypes, if handled type-correctly).
These are actually the kinds of things that make program maintenance considerably easier, since they allow more concise specifications of intended semantics to be done. No longer having to typecast (and thus expect run-time exceptions) when using a "vector of FooObjects" gives more power to the type checker, and thus allows a much richer class of programming errors to be detected at compile-time. This is the one major improvement in Java that's been missing since its very inception.

But note that "generics" or "parametric types" have been present in languages such as Eiffel or Sather for well over a decade, and for much longer in ML. In a way, it's embarrassing that such an essential feature was added this late during development.

Uglification?

[oblom]

Is anybody else irked by generics? One of the arguments in C++/Java discussion that I've read was: "Java removes complexity of C++, while remaining OOP". Well, generics remind me of C++ templates, which where a bit hard for me to swallow. Not to mention that attached to variable name doesn't make code any more attractive to look at.

It appears that Java's way to solve run time errors is to screw the bolts as tight a possible during compile time. Will generics become THE way, or just remain one of the options?

Re:Uglification?

[Anonymous Coward]

No, I'm not irked. Not even a little bit.

If your only experience of generics is C++, then all you've seen is the *worst* implementation of generics ever done in a language. Template code is almost unreadable. (Have you ever tried debugging one of the STL implementations?)

Besides, the lack of generic types cripples Java's ability to do static type checking, since your code ends up being full of things like this:

Foo f = (Foo) vector.elementAt(i);

where type errors can only be detected at runtime. That not only makes it impossible to detect errors at compile-time, it hurts performance at runtime.

Check out how generics are handled in Modula-3 for to see a much better way to handle them than C++ templates, or look at ML for something even more groovy (ML uses polymorphic type inference instead of generics, so you don't even have to mention types - the compiler just does the Right Thing).

Once you've worked with a good generic implementation, you'll never want to stop using them.

Harry

Re:Uglification?

[jameson]

Hi,

Well, generics remind me of C++ templates

They're not quite the same; C++ templates are essentially glorified preprocessor macros with
some relatively small checking and a rather baroque
underlying functional language. Generics are more
concrete than that.

Not to mention that attached to variable name doesn't make code any more attractive to look at.

It would be really neat to have type inference there ;-)

It appears that Java's way to solve run time errors is to screw the bolts as tight a possible during compile time.

That's the idea, and that's also what I try to do when writing programs. Why should I have to write half a dozen test suites for some simple program property if the type checker can tell me whether it'll work right?

Remember: Compilers don't do type checking just to optimise, but also to catch programming errors. And Generics allow you to catch a much more interesting class of these.

-- Christoph

Re:Write once, Rewrite forever?

[customiser]

AFAIK they will not be breaking existing code... If anything, they had to go out of their way (e.g. the ugly foreach statement) to ensure backward compatibility. In 1.4, the assert keyword might have caused problems, but now I don't think that's the case.

Retro...

[dance2die]

These new java features or shortcuts whatever reminds of C++... Is Java going to come with "Pointer" manipulation features later on? Will java become the next C++ and will be extremely tidious to program with? Overall, change is good... :)

One line summary

[Anonymous Coward]

Java adds four new syntaxes, Python's for loop, Perl type checking at compile time, something called 'metadata', and C enumerations, all of which impove compile time type checking at the expense of making the source code look and feel like perl.

compilers never make mistakes?

[cheezfreek]

As a compiler writer, I found this sentence to be particularly hilarious:

Because the compiler, unlike the programmer, never makes mistakes, the resulting code is also more likely to be free of bugs.

That's right, none of us has ever seen bad code generation or an internal compiler error. But, he does have a point. The compiler is less likely to make a mistake than a programmer.

not just sugar

[Anonymous Coward]

I think the new additions are great (except, perhaps, the autoboxing stuff). But I'm missing a fix for that extremely common javabean convention: get/set methods.

To add a property, say a String called name you have to write:

/**
* The name of this object.
*/
private String name;

/**
* The name of this object.
*/
public String getName() {
return name;
}

/**
* The name of this object.
*/
public void setName(String name) {
this.name = name;
}

That's 16 lines of code for one property! This is tedious to write, and more importantly, very hard to read when you have many properties.

This could easily be reduced to something like:

/**
* The name of this object.
*/
property String name;

expanded to exactly the same code as above by the compiler. Incredibly useful if you're, say, writing a lot of value objects in a j2ee scenario.

Re:not just sugar

[Jack Greenbaum]

That's 16 lines of code for one property! This is tedious to write, and more importantly, very hard to read when you have many properties.

You really need to try a generating/refactoring IDE like Eclipse. I once held to the orthodoxy that if I needed more than emacs then something was broken in the language. I grew up on object systems like CLOS where if you wanted a getter or setter you just asked for it in the definition of a field. So at first C++'s lack of public read-only/private read-write vars annoyed me, and Java's odd package visibility rules made me wince. But now I just declare private and generate my getters/setters, I navigate the file with the outline view, and I get more done per unit time then in any other language/ide pair, including VB.

-- Jack

Shorthand programming

[Shamashmuddamiq]

Yes, I'd agree with that remark about shorthand programming. I thought it was funny when I was teaching classes at UIUC to see stuff like this from the students:

#define FOREVER for(;;)
#define BEGIN {
#define END }
#define ONE 1
#define PUSHORT unsigned short *
#define DONE goto end

The first thing an amateur programmer does when assigned a new project in C/C++ is to go redefine the language and all the types. I scolded them for these kinds of things, knowing that once they were forced to read other people's code often that they would realize how stupid these kinds of things are. Unfortunately, once I started my career in embedded development, I quickly learned how stupid I must have been to think that people left these behaviors behind in college... (all the above examples are taken from "professional" code that I've seen in the last few weeks)

Re:Shorthand programming

[blahedo]

Your answer highlights the very reason that C macros are a bad idea. You say:

#define NOTHING ;
...
if ((flag & VAL1) || (flag & VAL2)
NOTHING;

Correct me if I'm wrong, but that's going to put two semicolons after the if---not itself an error, but it's going to block the else from working properly, since the second semicolon is a(n empty) statement after the end of the if clause!

In general, using macros in this fashion is dangerous and difficult to maintain, because it's not known what exactly is in the content of the macro. If a shortcut is at least part of a language, then a maintainer has some reasonable chance of understanding a piece of code as written without going hunting through header files. (Though of course one of the major complaints against perl is that there are so many shortcuts that are part of the language that nobody knows them all, pretty much reducing us to the previous problem.)

Re:Give billg his due...

[Hobbex]

One may say so. You see, C# had all features mentioned in article excluding generics since Beta 2. I think this is more than a year.

It's more that C# includes a bunch of features that some java programmers had been asking for, and so does java 1.5. It's not like any of these features were out the blue in C#, they are mostly things people have been missing from other languages.

Some quality stuff - competition is good!

[Fnkmaster]

I gotta say, I'm positively impressed. C# and Java are feeding features off of each other. Iterators, enumerators and autoboxing/unboxing - hmm, I think I've seen those before. Java 1.5 starts to look more and more like C#.

Some of this other stuff has been going on for ages - I'm curious about the metadata/declarative programming features. I've developed complete code generation systems for Java - the number of situations that require reams of very repetitive code in your average large-scale Java app is huge, and much of that can be automated. It would be great to see a consistent, standard system for doing this built in as a language feature rather than having hundreds of home-rolled systems everywhere, but the nature of many problems lends themselves to home-rolling. I can't tell you how many times I've written simple SAX parsers that spew out Java code, and rolled up an ant target to run it on some schema and package up the result. It's not clear from this brief example whether this is only for XML/RPC or whether there's an extensible metadata system that you can build on top of.

Then again, we should be careful not to roll too much into the language itself. I think generics, autoboxing, and enumerators are fabulous. Iterators I could give less of a shit over. Other stuff is great, but I question whether extending the language is the right mechanism. Much of the power and flexibility of Java comes from its simplicity. And most importantly, the ease of reading other people's code - there's far less stylistic variation because there are only N ways to do a task, rather than N! ways to do it, like in C++ (don't get me wrong, for a lot of tasks, I'd never dream of doing them in Java, like 3D programming). But it takes me about 1/4 to 1/3 the time to assimilate and learn a new Java API or library as it does to learn your average C++ API or library, and that's the appeal of Java.

Of course, I'll be thanking the gods that I never have to deal with the fugliness of casting and wrapping to move stuff between typed arrays and untyped Lists again.

Re:Everything must change...

[Grievance]

As others have pointed out, moving move type information into the declaration allows the compiler to help eliminate several kinds of type errors generated by programmers.

Now, if you want a weakly/dynamically/non-typed language, you should use one, and deal with the inevitable tradeoffs. It's not like there's a shortage of non-strongly-typed languages out there.

Re:Why I don't like Java

[forsetti]

Also, it's statically typed. It's so .. annoying to have to typecast everything

Typecasting is a tool -- do you really trust the compiler to recognize exactly what you mean in every scenario, throughout your hundereds of thousands of lines of code? I don't want to have the compiler (or run-time environment, or interpreter, whatever) to "guess" at what I mean -- I want to tell it exactly what I mean.

<flame> Perhaps this is why huge applications are usually written in languages requiring typecasting, and the "looser" languages are usually relegated to simple task duty.</flame> :)

Article didn't mention new concurrency stuff

[dood]

One of the coolest new features of JDK 1.5 is the completely reworked concurrency stuff (JSR 166). I just listened to Doug Lea (spec lead) give a talk on this very subject and I'm pretty convince this will rocket Java performance way up for a lot of the collections stuff, concurrent programming, etc.

Bascially, the goal of JSR 166 is to do for concurrency programming what JDK 1.2 did for data structurs (Collections stuff). The gist is, you'll never need to use "new Thread()" or "synchronized" anymore, but rather you'll execute Runnables, use Locks and Semaphores, etc. Also, queues are *completely* reworked to be ultra scalable.

JSR 166 is based on Doug's concurrency package:
http://gee.cs.oswego.edu/dl/classes/EDU/ oswego/cs/ dl/util/concurrent/intro.html

OH, and there will be classes like AtomicLong which guarantee atomic 'compare and set' options for primitives. :)

Cheers!

Re:Article didn't mention new concurrency stuff

[etedronai]

I am actually using the initial implementation of this on our current project and it is very nice. Actually have fine grained synchronization control makes it much easier to deal with a lot of thread synchronization problems. It has also helped us greatly reduce deadlock and detect deadlock because locks and waits can time out and report to you that they have timed out rather than just happily returning like Object.wait() does today. All in all this, along with generics, is probably the best new feature that is being added in jdk 1.5

How this compares to C++

[lkaos]

Generics
The new Java generics are really weak compared to C++ template support. This is probably partially due to difficult in compiler support and also complexity (templates are without a doubt the most complex feature of C++). I was disappointed though in Java generics mainly due to lack of any kind of specialization support and also about the strange paradigm used for Iterators (instead of an iterator being class defined with a consistant interface, it's an external class that just behaves that must wrap a behavior around the class).

Enhanced for loop
This is for_each() in C++. Now, with for_each, you have to use function objects which is arguable as to whether it's more readable. Fortunately, Boost has developed a boost::lambda class that allows for code to be used as the third parameter. This is _really_ neat.

Autoboxing/unboxing
I presume this means that primatives can't be used in generics.. That's kind of sad. This isn't a problem in C++.

Typesafe enums
This would be a nice linguistic pattern to have in C++. As it stands, the equivalent would be:

struct Coin { enum { penny, nickel, dime, quarter }; };

Static import
This can be achieved via using in C++. Of course, Java doesn't even really have a namespace paradigm so it's not really a fair comparision.

Metadata
This is.. well.. strange. I didn't see the syntax for doing something like this. If it is just keyword/code replacing, then an #include directive would work just as well.

Re:How this compares to C++

[TummyX]

Metadata
This is.. well.. strange. I didn't see the syntax for doing something like this. If it is just keyword/code replacing, then an #include directive would work just as well.


IMO, metadata is the coolest thing. It's a feature of C# which has had little recognition despite its coolness.

In both Java and C# you can use reflection to find out information about a class (class name, method names, etc). Attributes/metadata allow you to attach information to just about every element of a class/struct so that it can be queried dynamically using the reflection apis.

Imagine them as JavaDoc tags that aren't discarded at compile time but are instead compiled into a class's meta data. They'll do for source code what XML did for HTML -- give more meaning to the code.

Here's an example of using attributes/metadata to simplify XML serialization:

[XmlRoot("cat")]
public class Cat
{
[XmlAttribute("id")]
public string Name;

[XmlElement("color")]
public string Color;

public Cat()
{
}

public Cat(string name, string color)
{
this.Name = name;
this.Color = color;
}

public static void Main()
{
Cat cat = new Cat("felix", "yellow");

XmlSerializer serializer = new XmlSerialzer(typeof(Cat));

serializer.Serialize(cat, Console.Out);
}
}

The code yields the following output:

<cat id="felix">
<color>yellow</color>
</cat>

The C# XmlSerializer class dynamically generates the IL that will do the serialization so it is *very fast*. It knows how to map the field names to element/attribute names by inspecting the attributes.

Some other obvious uses include object/relational mapping (no need for external XML mapping files) and XMLRPC (just mark a method as Remotable!) etc. You can imagine infinite other uses for attributes/metadata.

I'm not sure how it works in Java but in C#, attributes are simply classes (usually with a name ending in 'Attribute'). You can define your own custom attributes and your own classes that work with them. It's very cool.

Problems with less verbose accessors

[MilesParker]

AC, I agree that the current approach is a PITA. I would also be very happy to see a more terse way to express properties. But what you are doing in your example, is throwing the baby out w/ the bathwater.

Note that you now don't have anyway to specify access and protection! I had given a little thought to better ways to handle this, and even had an interesting brief email exchange w/ a C# engineer about it. For the protection aspects you could do something like [this is just a quick idea I cam up with:]

property access String name;

where access is one of {read, write, readwrite}

But note taht right away you have a problem -- no way to assign protection levels to the various access, which is really a cross-product. What happens for example if you want the getter to be public, but the setter to be private?

Also, note that you would also need semantics to handle overriding the property accessors. You could just say that the property access defines an equivalent to the getter and setter methods, but that can get weird and confusing very quickly. Think about the situation where you have an interface defining getters and setters and then you implement it by just providing the one-line property definition. That would not be very transperent TSTL.

All this is just to say that it is a noble goal, but not as trivial as it sounds at first glance. IMO, the C# "solution" is particularly ugly, and qualifies strongly for the "syntactic sugar" label.

FInally, as in my other note, good IDEs like IntelliJ provide very convenient ways to auto-generate these things. I care much less about this issue now that I am not having to type all this stuff out by hand!

What Bjarne Stroustrup has to say about Java

[Q Who]

This is what he said about Java and the likes.

Also here.

I disagree - x++ vs ++x

[Pentagram]

x++ is the standard way of writing the statement, used by most coders in preference to ++x (in my experience anyway.) The fact that there is such a convention is reason enough to use it IMHO; if I see ++x in a piece of code, it's a warning that something unusual is going on.

As for your equality test examples, putting assignments in if statements in Java gives you a compile error. Also, it's quite rare to ever put a specific number in an if statement, and if you do it's likeley to be 0.

When will Java be 'frozen'?

[MarkWatson]

I have complained here before on this issue:

One of things that makes older more mature languages like Common Lisp (and perhaps Smalltalk) nice to work with is a feeling of both having really solid implementations and not breaking legacy code.

I like the idea of boxing and generics, but, these changes will affect old code (probably?) and the platform in general.

My vote would be to freeze the Java language (perhaps after 1.5) and concentrate on the following:

• memory footprint
• runtime efficiency

I would not like to see Java become a language designer's playground.

Because of great infrastructure software like servelt/JSP containers, (perhaps EJBs :-), XML utilities, solid web services support, etc. Java is a great platform.

Leave it alone (the sooner the better) except for improvements in the implementation.

-Mark

Re:When will Java be 'frozen'?

[_fuzz_]

My vote would be to freeze the Java language (perhaps after 1.5) and concentrate on the following:

* memory footprint
* runtime efficiency ...

Leave it alone (the sooner the better) except for improvements in the implementation.

This is a good idea. However, my vote is to concentrate on Java3. Screw backwards compatibility going forward and fix the standard library. Throw out the crap that has come along from JDK 1.0-1.1 and make the platform consistent. Why do we have both Enumerations and Iterators? Why are constants mostly UPPERCASE but sometimes lowercase (see java.awt.Color)? What about Thread.stop()?

This cruft is never going to go away until Sun releases a version of Java that isn't backwards compatible. Perl and Python do it. Java should too. It makes for a much cleaner language for new projects. Old projects may get stuck on a Java2 platform until the owners invest the time to convert them, but that's the way things go. It's time to clean out the cobwebs in Java and make better use of the new features.

Once all the old crap is gone, then it will be time to freeze the language and standard library.

I think these are all great...

[axlrosen]

... but man do I hate the enhanced for-loop syntax. At some point you have to give up perfect backwards-compatibility for readability. One or two new keywords would do a world of good.

for (TimerTask task : c)
task.cancel();

becomes

foreach (TimerTask task in c)
task.cancel();

Re:I think these are all great...

[sohp]

Sun has been burned once when they introduced the assert keyword and broke thousands of programs that use the JUnit testing framework. The bustage occured because JUnit already used the keyword as an identifier, for the assert() methods. A token can't be an identifier, so everyone's tests broke with 1.4 I applaud Sun from learning from that fiasco and avoiding a repeat.

JCP strikes again

[Wesley Felter]

Thanks a lot Sun for posting absolutely no information about the progress of this JSR. At least Doug Lea has posted a little information.

Re:what if...

[pmz]

what if microsoft buys sun?

What happens when matter meets anti-matter?

1) Microsoft wouldn't have a clue how to manage Sun. Sun is a hardware-engineering firm with a different corporate culture than Microsoft.

2) Most of Sun's employees would either quit or sight tight until they can quit.

3) Sun's customers would leave for IBM or HP; they would not eat MS' dog food.

4) The Justice Dept. would actually do something for once, because J2EE is the only big competitor to .NET, and Solaris is the biggest commercial competitor to Windows Server.

what if ibm buys sun?

Bye bye, UltraSPARC. This would probably alientate lots of Sun customers.

Java would cease being as open as it is. The JCP would close down.

Re:Hope it fixes issues with 1.4.x

[DogIsMyCoprocessor]

-1, troll

memory leaks (StringBuffer ToString anyone?).

Sorry, not a bug. What happened is the JDOM folks (gambling) relied on the internal implementation of StringBuffer and not its public API. That also broke JDOM for 1.2 jvms, which implemented StringBuffer differently. The internal implementation changed in 1.4.1, hosing the JDOM folks. Sun's only mistake was making this change in a minor version instead of a major one.

Re:Looking to Get Back into Java

[richieb]

If you are willing to spend some money check out IDEA from IntelliJ. It's great!

http://www.intellij.com/idea/

Re:ooooh baby

[slagdogg]

Typesafe enums. That alone makes me quiver with happiness.

You don't get out much, do you?

Just from pesonal experience..

[LogicHoleFlaw]

You know, I've just got to say this.

Each and every point on this list of additions to the languages addresses problems that I have personally run into in my use of Java at work. These things will make the writing and maintenance of java projects small and large much, much easier.

Generics: Thank you God, yes! Having to explicitly cast objects out of Containers is tedious and error-prone.

Iterators/Enhanced 'for': Make iteration much easier to read and understand.

Autoboxing/Unboxing: This helps alleviate the enormous kludge that is the Object/primitive dichotomy. Casting to and from wrapper types just to pass ints, etc. around really sucks.

static import: Not having to fully specify tedious class names to access static members is a big boon for making stuff digestible and easy to read.

Metadata: Writing boilerplate sucks the big one. How many hours have I lost writing boilerplate? Way too many. Having language support for generating code from the metadata cuts my implementation times way down.

I could sit here and argue with folks about the 'new Java' versus C++ or C# or Smalltalk or whatever endlessly. But man, these things sure make Java a whole lot more pleasant to use.

Yeah, but...

[Burpmaster]

I'd say that "++x" is actually the "best" way because it puts things in verb-noun order, which I'm used to as an English speaker.

In Soviet Russia, x++!

Uh, read the article

[autopr0n]

This is exactly what the new Java enums do. You just get to type a lot less and you can use them in case statements.

What about making the language useful

[samwhite_y]

In the old days when people talked about Linux, there was an expression "What about the big pink elephant in the middle of room" and it was referencing the fact that Linux did not support truetype fonts and font aliasing. Now some of that has been fixed, but Java still has its big pink elephant. Here are some of the things that people don't talk about.

The memory foot print for loading Java is 20meg + and growing. I am part of a team that has been developing a complex Java application for the last few years and we have created about a 3meg library (and it probably does at least as much as the more popularily used Java classes). I have looked at some of the source code for the core Java libraries and it is clear that a good rewrite could reduce this footprint by a factor of 2 to 4. Currently, C# loads with a footprint of 2 meg to 4 meg. Most other scripting languages usually have engines that are about the same size. To put it simply, the base core Java libaries are unjustifiably large. Maybe if Java were truly open source this could be addressed, but of course Sun doesn't even believe in submitting Java to a standards board.

You cannot load the Java VM once and run multiple processes (note "processes", not "threads") from the same Java VM memory footprint. I hear that such a thing is becoming possible for C# on Linux. You would have to build all the core Java classes into a "DLL" or ("so" on Linux), but that shouldn't be so difficult.

You still cannot do basic OS operations in Java without writing your own JNI library. The one that stands out is the inability to get the ID for the current running process. The "nio" package has corrected some of these issues, but the "nio" package should be the "io" package instead of having two separate packages (similar to AWT vs. Swing).

Window focus handling is still terrible. Ever have two frame windows up, have a modal dialog pop up on one frame while you were looking at the other? The frame window without the popop modal dialog becomes unresponsive and the other frame cannot be reached by tabbing through the windows. Only if you are lucky and that window is still visible on your desktop can you successfully reach it. Also, if a user clicks on a button that generates a modal dialog, the frame is only locked out from user input once the dialog manifests. This creates the infamous "double" clicking problem.

Java's package management is still primitive. If you want to do anything more subtle then using the classpath to load in custom libraries, you have to write your own class loader. Having an auxillary file specifying parameterizable rules for class loading would be nice. It would also be nice if you could ask a running Java process what packages it had loaded (and metadata about them such as location and version). Compare this to C# (or the way some of the web server oriented scripting languages work).

Some of the basic core library functions have some major weaknesses. For example, the Hashtable should be written as a native object when using String lookup keys and also allow you to dictate the algorithm for creating hashes (ex: use first 8 characters, last 8, or middle 8). There should also be a non thread safe version as well as a thread safe version. The lack of such a natively implemented primitive object is one of the big reasons why some less cleverly implemented scripting languages (such as python) can beat Java in performance on many web applications. In general, the core collection classes should be implemented in pure optimized (down to the actual chosen assembly code) native code.

Many of the utility libraries are broken in fundamental ways. Send back a badly formed response to the HTTP library and you go into an infinite loop when it falls into its keep-alive/retry logic. Date parsing is still behind what is available in the C standard library. Locale specifications do not allow you to independently specify date formats, language, floating point format, currency format, and time zone. You get o

Where are shared jar files/JVMs?

[Anonymous Coward]

When will Java support shared jar files that work like shared objects or DLLs in operation systems?
IMHO this is one the main shortcommings of Java. Every jar file is loaded into every process causing a huge memory footprint and long startup times.

When playing around with some java shells, that only load classes once and simulate processes as threads, I saw simple swing applications load in 0.1 secs and other significant speed ups.

I was hoping for it in 1.4.x and now it seems it won't even make it into 1.5. I realize that it will be hard to implement this in a platform transparent way.

if( xxx ) versus if( xxx )

[Baki]

I always get the creeps when I see if( xxx ).
It is as if "if" is a function putting the parentheses like that.

foo( xxx ) is a function call
if ( xxx ) is a statement which gets a block in parentheses.

I couldn't resist. I have to fight this good fight every day against some of my colleages.