How to initialize variable of type Vector<Term>[] in Java 5.0?

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Ulrich Scholz - 05 Dec 2005 14:00 GMT

Hi everybody.

In my project I create an array <code>atoms</code> in Java 5.0 that
holds elements of Type Vector<Term>. Term is some other class in my
project.

private Vector<Term>[] atoms;

In Eclipse, the assignment

atoms = new Vector[size];

gives the warning

Type safety: The expression of type Vector[] needs unchecked
conversion to conform to Vector<Term>[]

But

atoms = new Vector<Term>[size];

results in the error

Cannot create a generic array of Vector<Term>

How do I correctly initialize Vector <code> atoms</code> in Java 5.0?
Pointer to documentation welcome.

Thank you,

Uli

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Ian Pilcher - 05 Dec 2005 15:26 GMT

> How do I correctly initialize Vector <code> atoms</code> in Java 5.0?
> Pointer to documentation welcome.

@SuppressWarnings("unchecked")
private static Vector<Term>[] createAtoms(int size)
{
return (Vector<Term>[])new Vector[size];
}

Alternatively, use an ArrayList<Vector<Term>>.

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Ulrich Scholz - 05 Dec 2005 16:07 GMT

Thanks, that seems like a good reference.

Although,

Vector<Term>[] atoms = new Vector<?>[10];

Eclipse gives the compile time error

Type mismatch: cannot convert from Vector<?>[] to Vector<Term>[]

while the document has the example

List<String>[] lsa = new List<?>[10]; // unchecked warning - this is
unsafe!

Warning, not an error.

Uli

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Viator - 05 Dec 2005 15:27 GMT

Have a look at the document Section 7.3
http://java.sun.com/j2se/1.5/pdf/generics-tutorial.pdf

Hope it helps :-)

Amit

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Ulrich Scholz - 05 Dec 2005 16:09 GMT

Sorry, I replied to the wrong comment. copy of the above:

Thanks, that seems like a good reference.

Although,

Vector<Term>[] atoms = new Vector<?>[10];

Eclipse gives the compile time error

Type mismatch: cannot convert from Vector<?>[] to Vector<Term>[]

while the document has the example

List<String>[] lsa = new List<?>[10]; // unchecked warning - this is
unsafe!

Warning, not an error.

Uli

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Thomas Hawtin - 05 Dec 2005 17:26 GMT

> In my project I create an array <code>atoms</code> in Java 5.0 that
> holds elements of Type Vector<Term>. Term is some other class in my
> project.
>
> private Vector<Term>[] atoms;

Drop the use of reference arrays. Don't try to suppress errors or
warnings, if that can be avoided.

Just use:

private List<Vector<Term>> atoms;

atoms = new ArrayList<Vector<Term>>(num);
atoms.addAll(Collections.nCopies(num, null));

Tom Hawtin

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Unemployed English Java programmer
http://jroller.com/page/tackline/

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How to initialize variable of type Vector<Term>[] in Java 5.0?

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