What skills should a Core Java Developer have?

Overview

I have been trying to put together a list of basic skills a Java developer should have to move on to being an advanced Core Java programmer.

Skills

You;
  • can write code on paper which has a good chance of compiling.
  • can use a debugger to debug programs and profile an application.
  • are familiar all the primitives types and operators in Java.
  • understands the class loading process and how class loaders work
  • can use multiple threads both correctly and can prove this improve performance or behaviour. e.g. wait/notify/notifyAll, SwingUtils.invokeLater, the concurrency library
  • can use checked exceptions, generics and enums
  • can time a small benchmark and get reproducible results
  • can write a very simple client server TCP service
  • have an understanding of garbage collection, when is it triggered, what can you do to minimise it
  • understand when to use design patterns such as Singleton, Factory, Fly-weight, Builder, Object Pool, Iterator, Strategy, Visitor, Composite

Suggestions on how to get these skills

  • read Java Concurrency in Practice (http://jcip.net/)
  • write a simple client server TCP service such as chat
  • read up on Design Patterns and try to use them. http://www.oodesign.com/ so you can learn when they help and don't help

Comments

  1. Egor27 December 2011 at 17:32

    Profiling item is very interesting for me as I want to be advanced Java programmer. Are there any good resources about real world profiling techniques and what you should care of ( ex. how to do warm-up properly and etc)?

    ReplyDelete
  2. Vladimir Dolzhenko27 December 2011 at 21:32

    sounds a bit funny - advanced Core Java programmer have to avoid debugger usage which could lead to another behavior and results on multithreaded application.
    Could you imagine core java developer who doesn't pay attention to threads ? I'm not.

    ReplyDelete
  3. thibault28 December 2011 at 10:16

    Vladimir : An advanced core java programmer know the limitation of those tools and use it with care... Not using those tools when needed is absurd

    ReplyDelete
  4. Peter Lawrey28 December 2011 at 11:17

    @Egor, I would start with VisualVM doing CPU profiling and Memory profiling with a program you wrote. As @Thibault suggests, what does the profiler do well and what is its limitations. BTW: If you try a commercial profiler you may find it doesn't have these limitations.

    @Vladimar, I don't see why an advanced programmer would avoid using the debugger when trying to solve a bug. I have seen developers who always run their application in debug mode, which could be excessive. Your program should behave correctly with or without the debugger.

    I will add your suggestions about multi-threading.

    ReplyDelete
  5. Javier30 December 2011 at 07:06

    I'd add:
    - Understand class loading process and how classloaders work.
    Besides, I have to say that I've found a lot of people who have really problems with the concepts of classpath and working directory.
    - It reminds me that practice with Java IO and NIO would be a good requirement.
    - Knowledge of SPI architechture: from providing an implementation of an existing SPI to creating your own SPI.
    - Java Security. The topics cover in the Scott Oaks' book from O'reilly (Java Security 2nd edition), specially the security manager and access controller.

    You already mentioned, but I like to insist:
    - Concurrency. A core programmer must have read Java Concurrency in Practice (http://jcip.net/)
    - Network programming: sockets, URL connections and so on (yes, I used to love the O'Reilly books from the early 2000, like Java Network Programming, 3rd Edition)

    Additionally, some knowledge of JVM internals (garbage collection, bytecode generation, java memory model implementation...)

    I slightly disagree with the first two points. But it's difficult to provide an alternative.

    I mean, everybody can write code which compiles and debug it.

    But to become an advanced Core Java programmer I'd ask they can write "clean" OO Java Code. It includes a good management of Exceptions (including the use of unchecked exceptions, as the programmers from Springframework decided)

    [Apologize for all this speech, but I'm currently working in a project from 2002 that seems to use a SOP approach: Step Oriented Programming. Instead of creating objects to be called with messages/functions, the program is a sequential steps of the things that the programmers thought they need at each moment]

    ReplyDelete
  6. Peter Lawrey30 December 2011 at 08:43

    The SPI Architecure terminology is a bit specific to the cryptography library. I would prefer to put this in more general terms such a design patterns.

    ReplyDelete
  7. Javier30 December 2011 at 10:07

    I thought the same as you, but lately I've found SPI in a lot of topics.

    According wikipedia (http://en.wikipedia.org/wiki/Service_provider_interface): "In the Java Runtime Environment, SPIs are used in JDBC, JCE, JNDI, JAXP, JBI, Java Sound and Java Image I/O."

    But it's used elsewhere. Lately, I have needed to take a look to the Springframework's Converter SPI: http://static.springsource.org/spring/docs/current/spring-framework-reference/html/validation.html#core-convert

    That is what I meant with SPI. If you need to build some kind of system, SPI could be a good approach.

    ReplyDelete
  8. javin paul7 January 2012 at 13:48

    Most important skill which Java programmer need is programming and design ability. Java developer are mostly not very good on recursion,algorithms and basic datastructure concept as comapred to C or C++, may be rich Java API to blame for and on design they are little better.

    Javin
    2 Solution of OutOfMemoryError in Java

    ReplyDelete

Post a Comment

Popular posts from this blog

Java is Very Fast, If You Don’t Create Many Objects

Image
  You still have to watch how many objects you create. This article looks at a benchmark passing events over TCP/IP at 4 billion events per minute using the net.openhft.chronicle.wire.channel package in Chronicle Wire and why we still avoid object allocations..  One of the key optimisations is creating almost no garbage. Allocation is a very cheap operation and collection of very short-lived objects is also very cheap. Does this really make a difference? What difference does one small object per event (44 bytes) make to the performance in a throughput test where GC pauses are amortised? While allocation is as efficient as possible, it doesn’t avoid the memory pressure on the L1/L2 caches of your CPUs and when many cores are busy, they are contending for memory in the shared L3 cache.  Results Benchmark on a Ryzen 5950X with Ubuntu 22.10. JVM Vendor, Version No objects Throughput, Average Latency* One object per event Throughput, Average Latency* Azul Zulu 1.8.0_322 60.6 ...
Read more

System wide unique nanosecond timestamps

A Unique Identifier can be very useful for tracing. Those ids are even more useful when they contain a high-resolution timestamp.  Not only do they record the time of an event, but if unique can help trace events as they pass through the system. Such unique timestamps however can be expensive depending on how they are implemented.   This post explores a lightweight means of producing a unique, monotonically increasing system-wide nano-second resolution timestamp available in our open-source library. Uses for Unique Identifiers Unique identifiers can be useful to associate with a piece of information so that information can be referred to later unambiguously. This could be an event, a request, an order id, or a customer id. They can naturally be used as a primary key in a database or key/value store to retrieve that information later. One of the challenges of generating these identifiers is avoiding creating duplicates while not having an increasing cost.  You could ...
Read more

What does Chronicle Software do?

Image
Overview Chronicle Software is about simplifying fast data.  It is a suite of libraries to make it easier to write, monitor and tune data processing systems where performance and scalability are concerned. But its free, how do you make money, through support? We offer premium support . However, we often hear from users for the first time about a year after they have it in production.  Most users find they can support the software themselves.  It is only after a year or so, they have questions or concerns about where to take the product next.  In many cases, it is to a problem we have already solved and they just need to upgrade their software or use a new module we have added. As we don't know who is using most of our software, we can't advise them on how best to use our software and what updates or enhancements they would benefit from. We need users to contact us and ask questions.  We have a free forum , and we respond to 50% of questions in 2 hours...
Read more