Arrays.asList compilation problem

Question

I've used Arrays.asList dozens if not hundreds of times without problem. All of a sudden previously compiling code is failing to compile after switching to NetBeans 6.9 from 6.8. Here's a few lines in question:

Node n = new NickNode(4,5);
Node m = new NonLocatableNode();
Node subclass = new NickSubclassNode();

List<Node> nodes = Arrays.asList(n,m,subclass);

The subclasses of node are not important; they compile fine. The line that gives me an error is the Arrays.asList line. I get the error

alt text http://grab.by/grabs/b553ffb898ca0874ef4741b8c87fc576.png

I have no idea where it's getting anything about a HelpCtx.Provider[]... Does anyone see anything wrong with this snippet?

Replacing the asList line with

List<Node> theNodes = new LinkedList<Node>();
theNodes.add(n);
theNodes.add(m);
theNodes.add(subclass);

works fine. But I prefer the shorter syntax of Arrays.asList

Answer 1

尝试这个

List<Node> nodes = Arrays.<Node>asList(n,m,subclass);    

Answer 2

Your error graphic is not showing up for me but it looks like a generics problem. Perhaps a compiler warning was switched into a compiler error when you moved from netbeans 6.8 to 6.9?

Try declaring your List as ...

List<? extends Node> nodes = Arrays.asList(n, m, subclass);

The wildcard syntax specifies that the list contains Nodes and anything that inherits from Node.

Answer 3

Yep you are right this is the bug in NetBeans 6.9 which is already reported.So hopefully it will get resolved soon. You can see that bug report here

Answer 4

it should be:

List<? extends Node> nodes = Arrays.asList(n,m,subclass);

bear in mind that :

List<Sub Class> is not a sub class for List<Parent Class>

they are different classes.