Copy files in java gives me out of memory error

Canned <user@invalid.domain>
Tue, 25 Dec 2007 16:34:32 +0100
I'm trying to create a class which only jobs is to copy any text files
before its get opened by text editor. I build a constructor that will
read from file then store its content in textContent variable. From
there, copy method would read from textContent and write its content in
a new file. But instead of doing its job, I get "Exception in thread
"main" java.lang.OutOfMemoryError: Java heap space
    at java.util.Arrays.copyOf(
    at java.lang.AbstractStringBuilder.append(
    at java.lang.StringBuilder.append(
    at v1.CreateBackup.<init>(
    at v1.EditorSWT.openFileDialog(
    at v1.EditorSWT.access$0(
    at v1.EditorSWT$1.widgetSelected(
    at org.eclipse.swt.widgets.TypedListener.handleEvent(Unknown Source)
    at org.eclipse.swt.widgets.EventTable.sendEvent(Unknown Source)
    at org.eclipse.swt.widgets.Widget.sendEvent(Unknown Source)
    at org.eclipse.swt.widgets.Display.runDeferredEvents(Unknown Source)
    at org.eclipse.swt.widgets.Display.readAndDispatch(Unknown Source)
    at v1.EditorSWT.main(
Can someone please tell me what I'm doing wrong? I'm not very
experienced in Java

package v1;


public class CreateBackup {
    private String textContent;

    public CreateBackup(String fromFile) {
        try {
            File input = new File(fromFile);
            BufferedReader br = new BufferedReader(new FileReader(input));
            StringBuilder sb = new StringBuilder();
            String line = br.readLine();

            while (line != null) {
                sb.append(line + "\n");
            textContent = sb.toString();
        } catch (FileNotFoundException e) {
        } catch (IOException e) {

    public void copy(String toFile) {
        try {
            File output = new File(toFile);
            PrintWriter out = new PrintWriter(new BufferedWriter(new
        } catch (IOException e) {

*******this is how I call CreateBackup in main class*******************
private void openFileDialog() {
        FileDialog dialog = new FileDialog(shell, SWT.OPEN);
        String[] filterExt = {"*.txt", "*.rtf", "*.doc", "*.*"};
        String fileName =;
        // TODO Create backup file first before open the file
        String outFile = fileName + extension;
        CreateBackup backup = new CreateBackup(fileName);
        // Open the file
        try {
            File selectedFile = new File(fileName);
            if (selectedFile.isFile()) {
                try {
                    BufferedReader br = new BufferedReader(new FileReader(selectedFile));
                    StringBuilder sb = new StringBuilder();
                    String line = null;
                    while((line = br.readLine()) != null) {
                        sb.append(line + "\n");
                } catch (FileNotFoundException e) {
                } catch (IOException e) {
        } catch (NullPointerException e) {

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