from JSR-250-1.1.MREL section 2.5:
"The PostConstruct annotation is used on a method that needs to be executed after
dependency injection is done to perform any initialization. This method MUST be
invoked before the class is put into service."

Which I read as "may only get used by others after the @PostConstruct annotated method did run".

This is backed by the following example

public BeanA {
private @Inject BeanB b;
private int x = 0;
public int getX()

{ return x; }
@PostConstruct void init() { x = b.getX()+7; }
}

public BeanB {
private @Inject BeanA a;
private int x = 0;
public int getX() { return x; }

@PostConstruct void init()

{ x = a.getX()+9; }

}

which value do a.x and b.x get finally? This would simply be non-deterministic - and therefore forbidden by the JSR-250 spec.

Such kind of circular @PostConstruct method calls happen e.g. in CircularDependencyTest Pig -> Food -> Pig