OMG: Using a triple cast.

I have used double casts before but today found myself writing a triple cast. :P

The situation was; I need a method which returned the default value for a type.


public static <T> T nullValue(Class<T> clazz) {
   if (clazz == byte.class) 
      return (T) (Byte) (byte) 0;
   // other primitive types handled.
   return null;
}


Certainly this is casting madness. So I wrote the method a different way.


static {
   NULL_MAP.put(byte.class, (byte) 0);
   // other primitive types handled.
}

public static <T> T nullValue(Class<T> clazz) {
   return (T) NULL_MAP.get(clazz);
}


There the same casting is going on, but one cast is implied and the other two are seperated. Its not as ugly and more efficient. :)

Comments

  1. Anonymous17 June 2010 at 20:46

    > (T) (Byte) (byte) 0;
    Wow, you like autoboxing.
    (T) Byte.valueOf((byte)0); would be nices. Still ugly though (-:
    But more important IMO is that this way each time you call nullValue you create new instances of primitive types wrappers, which of pointless because they're immutable anyway.

    IMO the best part about your Map approach is that you don't create new instances of Byte, Integer etc anymore, so this is much more efficient.

    ReplyDelete
  2. Unknown18 June 2010 at 15:03

    valueOf() does not create new instances, it uses a cache internally. Also, I think it would be more correct to use Byte.TYPE, but I may be wrong here :)

    ReplyDelete
  3. Peter Lawrey19 June 2010 at 12:20

    @Nacho is correct for whole number types, (and Boolean) however for float and double, there is no cache so @mvmn is correct for these.

    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