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What is Double Brace initialization syntax ({{ ... }}) in Java?
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Double brace initialization is a combination of two separate process in java. There are two { braces involved in it. If you see two consecutive curly braces { in java code, it is an usage of double brace initialization. Java Double Brace Initialization. First brace is creation of an anonymous inner class.
For example, Java and C++ are often referred to as curly brace languages because curly braces are used to define the start and end of a code block.
Double brace initialisation creates an anonymous class derived from the specified class (the outer braces), and provides an initialiser block within that class (the inner braces). e.g.
new ArrayList<Integer>() {{ add(1); add(2); }}; Note that an effect of using this double brace initialisation is that you're creating anonymous inner classes. The created class has an implicit this pointer to the surrounding outer class. Whilst not normally a problem, it can cause grief in some circumstances e.g. when serialising or garbage collecting, and it's worth being aware of this.
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