Is Java's Double Brace Initialization Efficient?

Efficiency of Java "Double Brace Initialization"?

Main Question: Efficiency of Double Brace Initialization

Yes, double brace initialization (DBI) can be inefficient due to the generation of unnecessary class files. Each DBI instance creates an anonymous inner class, resulting in class file clutter and slow class loading. Additionally, garbage collection can be affected by DBI, and the memory cost for extra loaded classes can impact performance.

Second Question: Instance Initialization

The new HashSet is assigned to the "this" value in the instance initializer of the anonymous inner class. The inner class extends the class of the object being constructed by new, hence "this" references the instance being constructed.

Third Question: Obscurity and Use in Production Code

DBI can be considered obscure due to its unique syntax. While some consider it clear, explicit comments are recommended for clarity in production code.

Alternatives to Double Brace Initialization

• Arrays.asList: Creates a fixed-size list.
• Varargs methods: Simplify method argument lists.
• Google Collections: Offers methods for easily creating collections.
• Java 7 Collection literals: (not available in all Java versions) Provides concise collection initialization.
• Java 9 Set.of method: Offers a simple and efficient way to create Sets.

Conclusion

DBI can be an interesting curiosity, but it's generally not recommended for use in production code due to its potential inefficiency, class file clutter, and obscurity. Consider alternative methods for collection initialization to optimize performance and maintain code clarity.

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