using java codes in repository

What do you mean by "a repository"? Something like Git, SVN, ClearCase, etc?

I mean svn

I mean SVN.

Are you still there?

you're not supposed to run it from a svn repository, you keep your code there, so in case something goes wrong, you can revert back to a former version of the code. it's also to make things easier if you work on a group project, so that everybody has immediate access to the latest version, without going to ask everybody: "did you change something I need to know about?"

you should run your code (depending on the type of application) locally, after checking out, or on a server, after deploying it on said server.

I have checkedout the code I need. They are also compiled as they do not show anything in the written codes. I don't know how to run it. I converted all folders to maven and they are updated. One folder has two small letters of M and J on it (the folder matsim) But the other two just have M (playgrouds and mfeil folders).

At the same time. the class icons in the folder with M and J (matsim folder) have the symbol of "J Bold with the Blue Colour". But the classes in other two have the symbol of "outlined J and blue".

Is this right? There is a photo here if you want to look at.

they are .. compiled as they do not show anything in the written codes

what do you mean by that?

I don't know how to run it

you should run it the exact same way you run any other project in eclipse.

the 'M' stands for Maven, the 'J' for Java, btw.

just to be clear: whether your project is versioned using svn or any other versioning tool, does not change the slightest bit of how to compile and run them.

it looks like you don't know how to handle a project in eclipse, you don't know how to use Maven, and you don't know how to use a versioning tool, yet for some odd reason, you are trying to do all these things.

my advice: don't. start at the beginning, and learn one thing at the time.

I did try to run it with Run as/Maven Build...
But it cannot read pom.xml.

It seems this is getting to confusing.

I'm not surprised you find it confusing. You are jumping in at the deep end with a number of copmplex technologies all at once, without learning the basics first. Einstein would have found that difficult. (Actually he wouldn't because he was too smart to try it!)
Stultuske's advice (at the end of the previous post) is very good advice indeed.

Pom.xml defines the project dependencies. If you are just a beginner to java, then you have a TON of functionality to play with from the core libraries that come with the core JDK. Your IDE downloads whatever additional jar files your project needs by reading the pom file.