Efficiency of Java "Double Brace Initialization"?

🔥💻 Efficiency of Java "Double Brace Initialization"? 💻🔥

If you're a Java programmer, you may have come across a syntax called "Double Brace Initialization." 🤔

The syntax looks like this:

Set<String> flavors = new HashSet<String>() {{
    add("vanilla");
    add("strawberry");
    add("chocolate");
    add("butter pecan");
}};

This syntax creates an anonymous inner class with an instance initializer, which allows you to use any methods in the containing scope. 😮

But the main question is: is this syntax as inefficient as it sounds? Should you limit its use to one-off initializations? 🤔

Well, let's break it down and find some easy solutions. 😉

1️⃣ Is Double Brace Initialization inefficient?

While this syntax may appear inefficient, it's not as bad as it seems. 👍

The generated code actually runs quickly, but there are some downsides. The extra .class files clutter your JAR file and slightly slow down program startup. Additionally, garbage collection can be affected, and the memory cost for the extra loaded classes may be a factor in some cases. 😕

However, you can achieve the same effect of Double Brace Initialization using other alternatives like Arrays.asList, varargs methods, Google Collections, or even the proposed Java 7 Collection literals. Even newer JVM languages like Scala, JRuby, and Groovy offer concise notations for list construction that integrate well with Java. 🙌

Considering these drawbacks, if your code will pass on to developers who may not be familiar with Double Brace Initialization, it's a good idea to add occasional comments to make the syntax clearer. 😉

2️⃣ Mechanism behind the "this" reference

The second question raised in the context is about the mechanism behind the "this" reference in Double Brace Initialization. 🤔

In Double Brace Initialization, the anonymous inner class actually extends the class of the object being constructed by the new operator. This allows the inner class to have a "this" value referencing the instance being constructed. Pretty neat, right? 😎

3️⃣ Obscurity of the idiom in production code

Lastly, the question arises: is Double Brace Initialization too obscure to use in production code? 🤔

While it may not be the most widely used idiom, it does have its use cases. However, due to the clutter it adds to the classpath, the slight slowdown in class loading, and the coding obscurity it introduces, it may be better to avoid it in favor of other alternatives mentioned earlier. 😌

But if you enjoy Java semantics and like to surprise your developer friends, go ahead and spring Double Brace Initialization on them! 😉

In conclusion, Double Brace Initialization is an interesting and intellectually curious syntax in Java. While it may have its advantages, you should carefully consider its drawbacks and explore other alternatives. 🧐

Updated July 2017: 💡 Baeldung considers Double Brace Initialization an anti-pattern – check it out for more insights.

Updated December 2017: In Java 9, you can now use the Set.of syntax as a cleaner alternative to Double Brace Initialization. If you're stuck with an older version, consider using Google Collections' ImmutableSet. 🎉

So, what are your thoughts on Double Brace Initialization? Have you used it in your Java projects? Share your experiences in the comments below! 📝👇