Looks up specified games on steam, steamappidlookup package used by using ApplistEngine methods .addEntry(Integer) and getting an ArrayList<string> returned from .getEntries() to get strings formatted ###: "appname". THAT'S RIGHT I THROW UP EXCEPTIONS IN YOUR FACE, DEAL WITH IT.

ApplistEngine.java

package steamappidlookup;

// doesn't actually help us get any better compiled code
// only for testing's sake
import java.util.Map;
import java.util.HashMap;
import java.util.ArrayList;
import java.util.Scanner;
import java.net.URL;
import java.net.URLConnection;

public class ApplistEngine {
  private String getSTEAMApplistHTMLContents()
	{
		// find index of this: "app": [
		// find index of this: ] (STARTING BACKWARDS)
		// those are the bounds we need
		try 
		{
			URLConnection connection = new URL("http://api.steampowered.com/ISteamApps/GetAppList/v0001/").openConnection();
			Scanner scanner = new Scanner(connection.getInputStream());
			scanner.useDelimiter("\\Z");
			String content = scanner.next();
			int first = content.indexOf('[');
			int second = content.lastIndexOf(']');
			return content.substring(first + 2, second - 4);
		} 
		catch(Exception e) 
		{
			e.printStackTrace();
			return null;
		}
	}
	
	private HashMap<Integer, ApplistEntry> entries;
	
	public ApplistEngine()
	{
		entries = new HashMap<Integer, ApplistEntry>();
	}
	
	public void addEntry(Integer appid)
	{
		entries.put(appid, new ApplistEntry(appid));
	}
	
	public void addEntries(ArrayList<Integer> appidlist)
	{		
		for(Integer appid : appidlist)
		{
			entries.put(appid, new ApplistEntry(appid));
		}
	}
	
	private void getNamesandAddtoEntries()
	{
		// get names from JSON: api.steampowered.com/ISteamApps/GetAppList/v0001/
		String masterlist = getSTEAMApplistHTMLContents();
		for(Map.Entry<Integer, ApplistEntry> entry : entries.entrySet())
		{
			String appidprefix = "\"appid\": ";
			String nameprefix = "\"name\": ";
			int beginindex = masterlist.indexOf(appidprefix + entry.getKey().toString());
			if(beginindex != -1)
			{
				int namepos = beginindex + masterlist.substring(beginindex).indexOf(nameprefix);
				int endpos = namepos + masterlist.substring(namepos).indexOf('\n');
				String name = masterlist.substring(namepos + nameprefix.length(), endpos);
				entry.getValue().setName(name); 
			}
			else
			{
				System.out.println(entry.getKey().toString() + "failed searching?");
				System.out.println(appidprefix + entry.getKey().toString());
			}
		}
		
	}
	
	public ArrayList<String> getEntries()
	{
		getNamesandAddtoEntries();
		ArrayList<String> returnlist = new ArrayList<String>();
		
		for(Map.Entry<Integer, ApplistEntry> entry : entries.entrySet())
		{
			// the spaghetti
			returnlist.add(entry.getKey().toString() + ": " + entry.getValue().getName()); 
		}
		
		return returnlist;
	}
	
	
}

ApplistEntry.java

package steamappidlookup;

public class ApplistEntry
{
  private int appid;
	private String name;
	
	public ApplistEntry(int appid)
	{
		this.appid = appid;
	}

	public String getName() 
	{
		return name;
	}

	public void setName(String name) 
	{
		this.name = name;
	}

	public int getAppid() 
	{
		return appid;
	}
}

ExampleUsage.java

import java.util.ArrayList;
import steamappidlookup.*;

public class ExampleUsage {
  public static void main(String[] args)
	{
		ApplistEngine engine = new ApplistEngine();
		engine.addEntry(730); // CS:GO
		engine.addEntry(4830); // S.T.A.L.K.E.R.
		engine.addEntry(5070); // Dawn of War II Trailer 
		engine.addEntry(34440); // Civilization 4
		engine.addEntry(81181); // F1 2011 Trailer
		ArrayList<String> entries = engine.getEntries();
		for(String entry : entries)
		{
			System.out.println(entry);
		}
	}
}

/* output:
730: "Counter-Strike: Global Offensive"
81181: "F1 2011 Launch Trailer PEGI"
5070: "Dawn of War II: Trailer"
34440: "Sid Meier's Civilization IV"
4830: "S.T.A.L.K.E.R."
*/