Depends on what you mean by "work". For one thing, a jar is a Java archive file, not a folder.
Generally you add the jar to the Libraries folder of the project in the IDE - In Netbeans, simply right click on Libraries folder and select Add Jar/folder
Install bukkit
You have to open it with winrar.
When you open the .jar, you're then in the root, meaning the top 'level' which contains all the other folders and files.
download it then chuck its contents in a mods folder in minecraft .jar
If you are using window's, then use the Run program, and type in %appdata% and then run that, and it will bring you to a file containing the .minecraft folder.
You dont put them in your texture pack folder, hence the name "texture pack folder". You need to get a program such as 7ZIP or WINRAR and extract both the mod folder and MC jar. Drag ALL mod files in the MC Jar and delete "Meta-Inf"
in eclipse ide,.war,.jar files are kept inside lib folder
Do NOTHING!
I'd suggest downloading this file from Minecraft Mine. Go to the link below, and scroll down until you see "DOWNLOAD MINECRAFT 1.4.7 JAR CLIENT." Click this link to download. Make sure that you download the "client," not the "server."
You download the mod and open it with a archiving program, Win-rar is what I use but there is also 7-zip, then you have to find your .minecraft folder. You can find it by searching %appdata% in your start menu. Open the .minecraft folder then open the bin folder. Inside the bin folder, there is the .jar. Open it with a archiving program. Look at the mod. If there is a Readme file, open it and follow what it says to do. Also, there is usually the instructions on the page that you found the mod. If there isn't a Readme folder, then open the mod with the archiving program and copy all of the .classes into the .jar or your .minecraft folder. Caution: If you get a black screen when opening minecraft after installing the mod, then it is because you didn't delete the META-INF folder in your minecraft jar. Hope this was helpful. Ask me if there is any other problems. -Aiya