Remove all blank spaces and empty lines

Question

How to remove all blank spaces and empty lines from a txt File using Java SE?

Input:

qwe
    qweqwe
  qwe



qwe

Output:

Answer 1

Used to remove empty lines in same the file.

public static void RemoveEmptyLines(String FilePath) throws IOException
{
    File inputFile = new File(FilePath);
    BufferedReader reader = new BufferedReader(new FileReader(inputFile));
    String inputFileReader;
    ArrayList <String> DataArray = new ArrayList<String>();
    while((inputFileReader=reader.readLine())!=null)
    {
        if(inputFileReader.length()==0)
        {
            continue;
        }
        DataArray.add(inputFileReader);
    }
    reader.close();

    BufferedWriter bw = new BufferedWriter(new FileWriter(FilePath));
    for(int i=0;i<DataArray.size();i++)
    {
        bw.write(DataArray.get(i));
        bw.newLine();
        bw.flush();
    }
    bw.close();
}