EDIT: I'm still working on the launcher, but I found a launcher called Magic Launcher, that supports plugins.
I made a new version of my launcher that supported plugins, but you still need to delete META-INF -
if that is alright with everyone, I'll post that version. Otherwise I'll keep working on it privately.

I am working on a custom Minecraft launcher.
Download it and test it and tell me if there's any bugs!!
Any suggestions for features would be appreciated.

Link: http://www.freespace.com.au/filehosting/140600

EDIT: Here is a version for people using Java 6:
http://www.freespace.com.au/filehosting/428608
Current version: http://www.freespace.com.au/filehosting/622480
(I managed to recompile all of the launcher)

I restarted development using this version of the launcher:

Here's your first bug report:

JVM Launcher: Could not find the main class: net.minecraft.MinecraftLauncher. Program will exit.

EDIT: Fixed a spelling error.

Ran just fine on Windows 8 using java -jar q3h_minecraft.jar.

what the heck. then why am I getting this?

Exception in thread "main" java.lang.UnsupportedClassVersionError: net/minecraft
/MinecraftLauncher : Unsupported major.minor version 51.0
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClassCond(Unknown Source)
at java.lang.ClassLoader.defineClass(Unknown Source)
at java.security.SecureClassLoader.defineClass(Unknown Source)
at java.net.URLClassLoader.defineClass(Unknown Source)
at java.net.URLClassLoader.access$000(Unknown Source)
at java.net.URLClassLoader$1.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
Could not find the main class: net.minecraft.MinecraftLauncher. Program will exit.

What version of Java are you using??
I *think* you will need Java 7 for it to work.

Also, try disconnecting your internet and then running it.
I have made some changes to the offline mode of it.

Can I ask what the main purpose of this launcher is? If it's just an app to launch it with the proper java options then I can understand it, but if it's used to circumvent the online mode of Mojangs servers then I am afraid we can't allow it here. Could you perhaps detail out the functions of the launcher?

I am writing it because I am not connected to the internet most of the time I play MineCraft, and I like to play on my own bukkit server on LAN. But it just says I'm called 'Player', so I fixed that.

If it does allow you to play while connected to the internet, but with wrong account details, please tell me!!

Also, I am trying to make it load in additional jar files before minecraft.jar, so that I can for example load SinglePlayerCommands, without having to place the files inside minecraft.jar, but I haven't implemented this yet.

Turns out Java 7 in fact *is* needed. q3hardcore, it does attempt to validate when there is an internet connection present so I say that it works.

I also don't think that daisychaining code like that is a good idea...

dumb question ,is there a "offline" version of Minecraft? ( keep in mind,i know NOTHING about Minecraft ), my brother asked me to find out. thx

The official Minecraft client does not support offline mode, as it would be possible to abuse it and play on 'offline mode' servers (like mine)
That is why the OP is creating this client, so that they can play without internet.
There are other launchers that can do this already, but this one is designed for offline SinglePlayer only, and the other launchers are designed with piracy in mind.

I have done extensive testing of "daisychaining code" and have encountered no problems.
The only thing is that if you have "mods for mods", such as a mod that requires ModLoader, but must be placed in minecraft.jar to work, then you need to place the mod inside the same zip as ModLoader.

I use a batch file that puts the mods in the classpath, before minecraft.jar and lwjgl, then I directly launch the MineCraft applet. This however provides no opportunity to login, however you can still specify a name. So I am trying to implement this functionality in a launcher.

That's kind of why I said that, it would break mods such as IndustrialCraft and BuildCraft.

so where do i download the client? thx

Reading helps.

I have downloaded source code of some other people's MineCraft launchers.
I am going to see if I can add any features like they have.

If anyone has suggestions, please tell me!!

Just an FYI, I discovered that the Windows copy of Minecraft has an offline launcher. It's as simple as trying to log in and then hitting "play offline"
I don't know if the Mac or Linux versions have this, but if they do, then this thread would not be needed.

I know that there already is an "offline launcher" built into the official MineCraft launcher.
But it ignores the name that you type in and just calls you "Player".
So when I join the bukkit server I run on my LAN, it says I'm Player, not q3hardcore.
I made my launcher so that it will use the name that you typed in.

Try running it like this: "java -Xmx1024M -Xms1024M -jar q3h_minecraft.jar"
And tell me if you see any errors.