I'm coming from a c# background, how do generics look in java compared to c#? (basic usage)
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This might help stackoverflow.com/questions/864773/…Zak– Zak2010-01-06 17:10:14 +00:00Commented Jan 6, 2010 at 17:10
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2 Answers
That's a pretty huge question, to be honest - the biggest differences aren't in syntax, but in behaviour... at which point they're really, really different.
I would suggest you read through the Sun generics tutorial and Angelika Langer's Java Generics FAQ. Forget everything you know about generics from C#/.NET first though. In particular, while .NET generic types retain the type argument at execution time, Java generics don't due to type erasure.
So in other words, in C# you can write:
public class GenericType<T>
{
public void DisplayType()
{
Console.WriteLine(typeof(T));
}
}
... you can't do this in Java :(
Additionally, .NET generics can have value type type arguments, whereas Java generics can't (so you have to use List<Integer> instead of List<int> for example).
Those are probably the two biggest differences, but it's well worth trying to learn Java generics from scratch instead of as a "diff" from C#.
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There are a number of articles about this, but there's one notable example that discusses some of the differences and limitations of generics in Java.
Here is a simple example taken from the existing Collections tutorial:
// Removes 4-letter words from c. Elements must be strings
static void expurgate(Collection c) {
for (Iterator i = c.iterator(); i.hasNext(); )
if (((String) i.next()).length() == 4)
i.remove();
}
Here is the same example modified to use generics:
// Removes the 4-letter words from c
static void expurgate(Collection<String> c) {
for (Iterator<String> i = c.iterator(); i.hasNext(); )
if (i.next().length() == 4)
i.remove();
}
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