File editing program

I have written a Java class to replace text in file. The file contains database configurations and is as follows:

test.properties

#local
db.url=jdbc:oracle:thin:@localhost:test

#db.user=testa
#db.password=testa

db.user=testb
db.password=testb

#db.user=testc
#db.password=testc

# is a comment character. Now db schema testb is in use.

Here is my Java class to switch between schemas

import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.FileReader;
import java.io.IOException;
import java.util.HashMap;
import java.util.Map;

public class SwitchTo
{
  public static void main(String[] args)
  {
    Map schemaMap = new HashMap();
    schemaMap.put("a", "testa");
    schemaMap.put("b", "testb");
    schemaMap.put("c", "testc");

    String newText = "";
    for (int i = 0; i  entry : schemaMap.entrySet())
      {
        System.out.println(entry.getKey() + " for " + entry.getValue());
      }
      return;
    }

    try
    {
      BufferedReader file = new BufferedReader(new FileReader("test.properties"));
      String total = "";
      String line = "";
      while ((line = file.readLine()) != null)
      {
        if (!line.startsWith("#") && line.contains("db.user"))
        {
          line = "#" + line;
        }

        if (!line.startsWith("#") && line.contains("db.password"))
        {
          line = "#" + line;
        }

        if (line.startsWith("#") && line.contains(newdb))
        {
          line = line.substring(1);
        }

        total = total + line + "\n";
      }

      FileOutputStream File = new FileOutputStream("test.properties");
      File.write(total.getBytes());
      System.out.println("Switched to schema " + schemaMap.get(newText));
    }
    catch (FileNotFoundException e)
    {
      e.printStackTrace();
    }
    catch (IOException e)
    {
      e.printStackTrace();
    }
  }
}

and I have created a batch file to run this program from command

Actually, this can be more generic.

Instead of hard-coding your map; fill it from your properties file.

So change your prop file to :

#db.id=a
#db.user=testa
#db.password=testa

db.id=b
db.user=testb
db.password=testb

Fill your map like this :

private Map schemaMap = new HashMap();

public void fillMap() throws FileNotFoundException, IOException {
    String line;
    String key = null;
    String value = null;
    try (BufferedReader file = new BufferedReader(new FileReader("test.properties"))){
        while ((line = file.readLine()) != null) {

            if (line.contains("db.id")) {
                key = line.substring(line.indexOf('='));// could be you have to do an + 1
            }
            if (line.contains("db.user")) {
                value = line.substring(line.indexOf('='));
            }
            if (key!=null && value != null) {
                schemaMap.put(key, value);
                key = null;
                value = null;
            }
        }
    } catch (IOException ex) {
         // report with Logger or System.out what happend.
    }
}

Secondly : In your main you use the args.

You do not check for how many args you have, you just take the last arg.

Maybe a check for how many args you have is appropriate here, and make the program do what you want then. (like quitting with error message or taking default arg).

Third : Always close your resources(reader/writer in this case).

Here it is done with a Try-with-resources available from java 7, otherwise you will need a finally block where you close it in.

StackExchange Code Review Q#48122, answer score: 12