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Create a portion of a Vector in Java

开发者 https://www.devze.com 2023-03-31 08:01 出处:网络
I have a Vector< MyClass > myvector;with size 0 - 400 and I\'d like my method to return a new Vector with the positions 0-100 if exists. But my code:

I have a Vector< MyClass > myvector; with size 0 - 400 and I'd like my method to return a new Vector with the positions 0-100 if exists. But my code:

return (Vector< MyClass >) myvector.sublist( 0, Math.min(myvector.size,100) );

crashes with at the return line.

ERROR/AndroidRuntime(2053): java.lang.Cl开发者_C百科assCastException: java.util.Collections$SynchronizedRandomAccessList

What am I doing wrong? how can I fix it?

Thanks in advance


Vector<MyClass>.subList() returns a List<MyClass>. List<MyClass> cannot be converted to a Vector<MyClass>.

It's often suggested that, in general, you should work with references-to-interface-types, not references-to-concrete-types wherever possible. Following this advice avoids this sort of conundrum.


The return type of Vector.subList is not necessarily of class Vector, but rather an implementation of a List. You can solve this problem by:

return new Vector<MyClass>(myvector.subList(0, Math.min(myvector.size(), 100)));

Edit: Thanks Stjepan and Steve for noting the unnecessary conditional.


Sublist is returning a List if you want to do this you will have to do this:

new Vector(myList);


because sublist returns a list not a vector

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