Description Sotirios Delimanolis 2015-06-10 11:46:23 EDT

When you access a constant variable class field through an enum constant, the corresponding enum type is not initialized.

Take this code:


public class Example {
    public static void main(String[] args) throws Exception {
        Object p = EnumType.ENUM_CONSTANT.CONSTANT_VARIABLE;
    }
}

enum EnumType {
    ENUM_CONSTANT;
    EnumType() {
        System.out.println("initialized");
    }
    public static final String CONSTANT_VARIABLE = "a value";
}

When you run it, nothing is printed to standard out. I expect "initialized" to be printed since we're accessing "ENUM_CONSTANT" which should trigger initialization of EnumType. In this case, the compiler seems to remove the access altogether since we're accessing a static field.

According to the JLS (http://docs.oracle.com/javase/specs/jls/se8/html/jls-15.html#jls-15.11.1), concerning field access expressions

> If the field is static: (a) The Primary expression is evaluated, and the result is discarded. [...]

The enum constant should be used, triggering initialization, and discarded. 

The Oracle compiler pushes a reference to the constant on the stack, then pops it. It then pushes the value of the constant on the stack so it can be stored in the local variable.

I've reproduced this only on 

Version: Luna Service Release 2 (4.4.2)
Build id: 20150219-0600