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KDTree Implementation in Java

I’m looking for a KDTree implementation in Java.
I’ve done a google search and the results seem pretty haphazard. There are actually lots of results, but they’re mostly just little one-off implementations, and I’d rather find something with a little more “production value”. Something like apache collections or the excellent C5 collection library for .NET. Something where I can see the public bug tracker and check to see when the last SVN commit happened. Also, in an ideal world, I’d find a nice well-designed API for spatial data structures, and the KDTree would be just one class in that library.

For this project, I’ll only be working in either 2 or 3 dimensions, and I’m mostly just interested in a good nearest-neighbors implementation.

Answer

In the book Algorithms in a Nutshell there is a kd tree implementation in java along with a few variations. All of the code is on oreilly.com and the book itself also walk you through the algorithm so you could build one yourself.

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When’s the absolute latest you can call Page.ClientScript.RegisterClientScriptBlock?

I need to output some JavaScript in a WebControl based on some processing and some properties that the consumer can set, doing it on the load of the page will be to early.

When is the latest I can call RegisterClientScriptBlock and still have it output on the page?

Answer

OnPreRender

or, if you override Render…. before calling “base.Render”

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Tips for using Vim as a Java IDE? [closed]

I’m addicted to Vim, it’s now my de facto way of editing text files.

Being that it’s mainly a text editor and not an IDE, has anyone got tricks for me to make it easier when developing Java apps?

Some questions I have:

  • How do I invoke a maven task without leaving vi?
  • Can I get code completion?
  • How’s the syntax highlighting?

Anything else (other than “Don’t do it!”) that I should know about?

Answer

Some tips:

  • Make sure you use vim (vi improved). Linux and some versions of UNIX symlink vi to vim.
  • You can get code completion with eclim
  • Or you can get vi functionality within Eclipse with viPlugin
  • Syntax highlighting is great with vim
  • Vim has good support for writing little macros like running ant/maven builds

Have fun šŸ™‚

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Javascript – how to replace a sub-string?

This is a simple one. I want to replace a sub-string with another sub-string on client-side using Javascript.

Original string is 'original READ ONLY'

I want to replace the 'READ ONLY' with 'READ WRITE'

Any quick answer please? Possibly with a javascript code snippet…

Answer

String.replace() is regexp-based; if you pass in a string as the first argument, the regexp made from it will not include the ā€˜gā€™ (global) flag. This option is essential if you want to replace all occurances of the search string (which is usually what you want).

An alternative non-regexp idiom for simple global string replace is:

function string_replace(haystack, find, sub) {
    return haystack.split(find).join(sub);
}

This is preferable where the find string may contain characters that have an unwanted special meaning in regexps.

Anyhow, either method is fine for the example in the question.

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Java Generics (Wildcards)

I have a couple of questions about generic wildcards in Java:

  1. What is the difference between List<? extends T> and List<? super T>?

  2. What is a bounded wildcard and what is an unbounded wildcard?

Answer

In your first question, <? extends T> and <? super T> are examples of bounded wildcards. An unbounded wildcard looks like <?>, and basically means <? extends Object>. It loosely means the generic can be any type. A bounded wildcard (<? extends T> or <? super T>) places a restriction on the type by saying that it either has to extend a specific type (<? extends T> is known as an upper bound), or has to be an ancestor of a specific type (<? super T> is known as a lower bound).

The Java Tutorials have some pretty good explanations of generics in the articles Wildcards and More Fun with Wildcards.

Source: stackoverflow
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