Setting heap size

Question

I hope you will all forgive me because this has been exhausted although I followed all the advices.
After the following examples, to check my own environment. I have done the following:
long heapSize = Runtime.getRuntime().totalMemory();
    System.out.println(heapSize);
    // Get maximum size of heap in bytes. The heap cannot grow beyond this size.
    // Any attempt will result in an OutOfMemoryException.
    long heapMaxSize = Runtime.getRuntime().maxMemory();
    System.out.println(heapMaxSize);
    // Get amount of free memory within the heap in bytes. This size will increase
    // after garbage collection and decrease as new objects are created.
    long heapFreeSize = Runtime.getRuntime().freeMemory();
    System.out.println(heapFreeSize);
        Which outputs is:
5177344
66650112
4437824
Currently, it looks like my heap cannot grow more than 6.6M right?
Now if I want to increase my maximum heap size, the command is adviced to be:
java -Xmx128m readFile.class
However, it keeps coming oout with an error:
Exception in thread "main" java.lang.NoClassDefFoundError: readFile/class
Where did that "main" come from? The only thing that I have done is that I have another class called myMain which calls this clss for test purposes.
The class which raised this heap problem was a class I was using to read files as in the bellow:
import java.io.*;
import java.util.*;
import java.util.regex.*;
public class readFile
private ArrayList<String>  dataFromFile= new ArrayList<String>();
    public String readFile(String fileNameIn, String encoding) throws IOException {
    BufferedReader in = new BufferedReader(new InputStreamReader(
      new FileInputStream(fileNameIn), encoding));
      buffer = new StringBuffer();
    int i;
    while((i = in.read()) != -1) buffer.append((char)i);
    in.close();
    return buffer.toString();
//return an array of each data read from file separated by a tab etc
  public ArrayList<String> getRecords(String fileNameIn) throws IOException {
      String  s = this.readFile(fileNameIn);
      String current;
      Pattern p = Pattern.compile("[^\t\n]+|\t(?=\t)|\t$",
      Pattern.CASE_INSENSITIVE);
      Matcher m = p.matcher(s);
      while(m.find()){
         current = m.group(0).trim();
         dataFromFile.add(current);
        }//while 
    return dataFromFile;
}Message was edited by:
McTaar
Message was edited by:
McTaar

Answer 1

This is the error displayed:
java.lang.OutOfMemoryError: Java heap space
     at java.util.Arrays.copyOf(Arrays.java:2760)
     at java.util.Arrays.copyOf(Arrays.java:2734)
     at java.util.ArrayList.ensureCapacity(ArrayList.java:167)
     at java.util.ArrayList.add(ArrayList.java:351)
     at readFile.getRecords(readFile.java:41)
     at myMain.main(myMain.java:79)readFile: 41 is
dataFromFile.add(current);