Java SE (Java Platform, Standard Edition)

I have a Jtextarea and keypad, the keypad is used to enter text to the JtextArea. I have a button on the keypad that is used for two things:
1. To move back through the text
2. To delete a character at a time

I do not kno how to go about deleting a character at a time, i have tried using deletCharAt() and giving the position to delete.

int count = 0;
System.out.println("pressed BCK");
 txtmsg = (display.getText());
count = txtmsg.length();
System.out.println(count);
        		    
		if (e.getSource()==keys[9])
		{
			System.out.println("pressed BCK twice - DELETE");
			txtmsg.deleteCharAt(count);
			display.setText(display.getText());
		}

This results in the following error cannot find symbol method deleteCharAt().
Txtmsg is a variable of type string, and display is the name for the JtextArea.

Any help appreciated, thanks.