When you serialize this class and deserialize it, you still have to cast the type using SerializedData in. It’s not just a HashMap, it’s a HashMap with type information. And when you operate on incompatible types, the program won’t compile. If you want to understand it better and aren’t very familiar with generics, I encourage viewing the edit history of this answer. Rick Rick 3, 1 21 After all, this is what the “unchecked cast” warning wants to tell us: Awesome; I think I can combine that with my answer to parameterize it and avoid having to suppress warnings altogether! Basically, make the unsafe cast, and suppress the warning.
Glen on Programming: Checking an Unchecked Cast in Java 5 or Later
I will use SuppressWarnings “unchecked”. You can’t just check a parameterized type with instanceof, because the parameterized type information serialiable unavailable at runtime, having been erased at compile time. The source of the object is an API I have no control over code added.
I was just about make the same comment. Home Questions Tags Users Unanswered. Another solution, if you find yourself casting the same object a lot and you don’t want to litter your code with SupressWarnings “unchecked”would be to create a method with the annotation.
Take this one, it’s much faster than creating a new HashMap, if it’s already one, but still secure, as each element is checked against it’s type Plenty of legacy “SOA” implementations pass around various objects that you fo always trust. Sadly, even though the cast and the warning are for the assignmentthe annotation has to go on the variable declaration So suppressing the warning seems to be the only way to work around this without complicating the source code.
The server is running on a different machine, if a throw the exception on the server side, seriwlizable the client will never know that something went wrong. Sign up or log in Sign up using Google.
Instead of casting the list, just iterate it and cast each element, the warning will not appear, awesome. Unfortunately it’s not that easy a situation. What is it that I wrote that makes you think it does not? Here is an example:. In fact, I can’t imagine any reason to set the type of a variable to HashMap instead of Map. That’s a lot of work, possibly for very little reward Much more expensive bigger and higher-resolution monitors to give room to all those wasted lines, a bigger desk to put all those bigger monitors onto, a bigger room to put the bigger desk into, and an insightful boss.
It is clear to me why this warning occurs, but I have not come up with any solution on how to solve the problem without this warning save suppressing the warning. The objects are stored in an ArrayList called orders.
Unchecked utility function in the answer above by Esko Luontola is a great way to avoid program clutter. This means that it will turn into a traditional cast giving a ClassCastException right there in the event of an error. So suppressing the warning does the job. So, you have to check it yourself. Here is a shortened example that avoids the “unchecked cast” warning by employing two strategies mentioned in other answers. So if the declaration and the assignment are in different places say, outside and inside a ‘try’ block respectivelyEclipse now generates two warnings: Unchecked cast does not mean that you did not check the cast.
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That code works very well, but I do get a warning from the compiler in the next method in the line I marked. And when you operate on incompatible types, the program won’t compile. The warning is not just because the compiler does not know that the cast is safe.
Unchecking this box makes Eclipse and javac behave the same, serialiizable is what I wanted. In this particular case, I would not store Maps into the HttpSession directly, but instead an instance of my own class, which in turn contains a Map an implementation detail of the class.
This removed the warning but still I am not confident: I’d like to avoid Eclipse warnings, if possible, since theoretically they indicate at least a potential code problem. It’s not really dead code if it can potentially throw an exception. In general, the Java compiler knows the type of each variable, at every point during the execution.
It’s somewhat odd that Java’s collection framework has no iterator for recursive data structures. In that case you would have to use my first way.
Sign up or log in Sign up using Google. For type casting of a Collection, use the wildcard? You aren’t really buying anything there since you still have the single blind cast, but at least you can use generics from there on up so the JVM can help you avoid blind casts in other pieces of your code. His problem was not verification of the type, but a warning caused by a “put” into an uncasted map.
A warning is just that. I came up with a routine to actually check the cast to parameterized HashMap, which eliminates the unchecked cast warning: With no context it isn’t going to look very convincing, but anyway: I like the Josh Bloch Kool-Aid, but here are a couple of alternatives.