// Create the text component
JTextComponent tc = new JTextArea("Initial Text");

// Get length
int docLength = tc.getDocument().getLength();

// Get all text
String text = tc.getText();

try {
    // Get the first 3 characters
    int offset = 0;
    int len = 3;
    text = tc.getText(offset, len);

    // Get the last 3 characters
    offset = docLength-3;
    len = 3;
    text = tc.getText(offset, len);
} catch (BadLocationException e) {
}