Remove all blank spaces and empty lines

How about something like this:

FileReader fr = new FileReader("infile.txt"); 
BufferedReader br = new BufferedReader(fr); 
FileWriter fw = new FileWriter("outfile.txt"); 
String line;

while((line = br.readLine()) != null)
{ 
    line = line.trim(); // remove leading and trailing whitespace
    if (!line.equals("")) // don't write out blank lines
    {
        fw.write(line, 0, line.length());
    }
} 
fr.close();
fw.close();

Note - not tested, may not be perfect syntax but gives you an idea/approach to follow.

See the following JavaDocs for reference purposes: http://download.oracle.com/javase/7/docs/api/java/io/FileReader.html http://download.oracle.com/javase/7/docs/api/java/io/FileWriter.html

Have a look at trim() function

http://docs.oracle.com/javase/1.5.0/docs/api/java/lang/String.html#trim()

Also, some code would be helpful...

...
Scanner scanner = new Scanner(new File("infile.txt"));
PrintStream out = new PrintStream(new File("outfile.txt"));
while(scanner.hasNextLine()){
    String line = scanner.nextLine();
    line = line.trim();
    if(line.length() > 0)
        out.println(line);
}
...