The Java® Virtual Machine Specification, Java SE 7 Edition, Third Edition

5.5. Initialization

Initialization of a class or interface consists of executing its class or interface initialization method (§2.9).

A class or interface may be initialized only as a result of:

• The execution of any one of the Java Virtual Machine instructions new, getstatic, putstatic, or invokestatic that references the class or interface (§new, §getstatic, §putstatic, §invokestatic). All of these instructions reference a class directly or indirectly through either a field reference or a method reference.

Upon execution of a new instruction, the referenced class or interface is initialized if it has not been initialized already.

Upon execution of a getstatic, putstatic, or invokestatic instruction, the class or interface that declared the ...