djspiewak

Quick Tips for Fast Code on the JVM

I was talking to a coworker recently about general techniques that almost always form the core of any effort to write very fast, down-to-the-metal hot path code on the JVM, and they pointed out that there really isn't a particularly good place to go for this information. It occurred to me that, really, I had more or less picked up all of it by word of mouth and experience, and there just aren't any good reference sources on the topic. So… here's my word of mouth.

This is by no means a comprehensive gist. It's also important to understand that the techniques that I outline in here are not 100% absolute either. Performance on the JVM is an incredibly complicated subject, and while there are rules that almost always hold true, the "almost" remains very salient. Also, for many or even most applications, there will be other techniques that I'm not mentioning which will have a greater impact. JMH, Java Flight Recorder, and a good profiler are your very best friend! Mea

teamdandelion

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prakhar1989

Rich Hickey on becoming a better developer

Rich Hickey • 3 years ago

Sorry, I have to disagree with the entire premise here.

A wide variety of experiences might lead to well-roundedness, but not to greatness, nor even goodness. By constantly switching from one thing to another you are always reaching above your comfort zone, yes, but doing so by resetting your skill and knowledge level to zero.

Mastery comes from a combination of at least several of the following:

nl5887

package service

import (
        _ "encoding/base64"
        _ "fmt"
        _ "net/http"
        "appengine"
        "appengine/urlfetch"
        "appengine/runtime"
        "time"

dushmis

public class CustomeClassLoader_T{
  static class CustomClassLoader extends ClassLoader {
		String host;
		int port;
		public Class findClass(String name) {
			byte[] b = loadClassData(name);
			return b!=null?defineClass(name, b, 0, b.length):null;//or throw, return null for this example
		}
		private byte[] loadClassData(String name) {
			// load the class data from the connection

klange

Since this is on Hacker News and reddit...

• No, I don't distribute my résumé like this. A friend of mine made a joke about me being the kind of person who would do this, so I did (the link on that page was added later). My actual résumé is a good bit crazier.
• I apologize for the use of _t in my types. I spend a lot of time at a level where I can do that; "reserved for system libraries? I am the system libraries".
• Since people kept complaining, I've fixed the assignments of string literals to non-const char *s.
• My use of type * name, however, is entirely intentional.
• If you're using an older compiler, you might have trouble with the anonymous unions and the designated initializers - I think gcc 4.4 requires some extra braces to get them working together. Anything reasonably recent should work fine. Clang and gcc (newer than 4.4, at le

deanet

#!/bin/bash

## uploading to google
## rev: 22 Aug 2012 16:07

det=`date +%F`
browser="Mozilla/5.0 (X11; Ubuntu; Linux i686; rv:13.0) Gecko/20100101 Firefox/13.0.1"
username="[email protected]"
password="password"
accountype="HOSTED" #gooApps = HOSTED , gmail=GOOGLE

earthgecko

#!/bin/bash
# bash generate random alphanumeric string
#

# bash generate random 32 character alphanumeric string (upper and lowercase) and 
NEW_UUID=$(cat /dev/urandom | tr -dc 'a-zA-Z0-9' | fold -w 32 | head -n 1)

# bash generate random 32 character alphanumeric string (lowercase only)
cat /dev/urandom | tr -dc 'a-z0-9' | fold -w 32 | head -n 1

gre

/*
 * This work is free. You can redistribute it and/or modify it under the
 * terms of the Do What The Fuck You Want To Public License, Version 2,
 * as published by Sam Hocevar. See the COPYING file for more details.
 */
/*
 * Easing Functions - inspired from http://gizma.com/easing/
 * only considering the t value for the range [0, 1] => [0, 1]
 */
EasingFunctions = {

darktable

application: you-app-name-here
version: 1
runtime: python
api_version: 1

default_expiration: "30d"

handlers:
- url: /(.*\.(appcache|manifest))
  mime_type: text/cache-manifest