Someone

	public void actionPerformed(ActionEvent e){

				if(e.getSource() == but1)
				{
					addDigitToDisplay(but1);
				}
				else if(e.getSource() == but2)
				{
					addDigitToDisplay(but2);
				}
				else if(e.getSource() == but3)
				{
					addDigitToDisplay(but4);
				}
				else if(e.getSource() == but5)
				{
					addDigitToDisplay(but5);
				}
				else if(e.getSource() == but6)
				{
					addDigitToDisplay(but6);
				}
				else if(e.getSource() == but7)
				{
					addDigitToDisplay(but7);
				}
				else if(e.getSource() == but8)
				{
					addDigitToDisplay(but8);
				}
				else if(e.getSource() == but9)
				{
					addDigitToDisplay(but9);
				}
				else if(e.getSource() == but0)
				{
					addDigitToDisplay(but0);
				}

	}


	void setDisplayString(String s){
		LabelOutPut.setText(s);
	}

	String getDisplayString (){
		return LabelOutPut.getText();
	}

	void addDigitToDisplay(int digit){
		if (clearOnNextDigit)
			setDisplayString("");

		String inputString = getDisplayString();

		if (inputString.indexOf("0") == 0){
			inputString = inputString.substring(1);
		}

		if ((!inputString.equals("0") || digit > 0)  && inputString.length() < MAX_INPUT_LENGTH){
			setDisplayString(inputString + digit);
		}


		displayMode = INPUT_MODE;
		clearOnNextDigit = false;
	}