I'm a beginner and trying to make a simple calculator. i've searched for other answers but my problem is that after pressing the operator it's just keeps the first string only
public class CalculatorFrame extends JFrame { public CalculatorFrame(){ this.setTitle("Calculator"); this.setLayout(new BorderLayout(2,2)); MenuBar menuBar = new MenuBar(); JTextArea txtArea = new JTextArea(); txtArea.setEditable(false); txtArea.setComponentOrientation(ComponentOrientation.RIGHT_TO_LEFT); txtArea.setText("0"); txtArea.setFont(new Font("Sans Serif", Font.PLAIN,30)); JPanel panel = new JPanel(); panel.setLayout(new GridLayout(4,3,2,2)); JPanel panel2 = new JPanel(); panel2.setLayout(new GridLayout(6,1,2,2)); MyActionListener al = new MyActionListener(txtArea); MyOperatorListener ol = new MyOperatorListener(txtArea); JButton btn = new JButton(); int k=10; for (int i=0; i<3; i++) { k=k-3; for (int j=0; j<3; j++) { btn = new JButton(Integer.toString(k++)); btn.setPreferredSize(new Dimension(70, 60)); btn.setBackground(new Color(224,224,224)); btn.setBorder(BorderFactory.createRaisedSoftBevelBorder()); btn.setFont(new Font("Sans Serif", Font.BOLD,20)); btn.addActionListener(al); panel.add(btn); } k=k-3; } JButton btn7 = new JButton("0"); btn7.addActionListener(al); btn7.setBackground(new Color(224,224,224)); btn7.setPreferredSize(new Dimension(70, 60)); btn7.setBorder (BorderFactory.createRaisedSoftBevelBorder()) ; btn7.setFont(new Font("Sans Serif", Font.BOLD,20)); JButton btn8 = new JButton("."); btn8.addActionListener(al); btn8.setBackground(new Color(224,224,224)); btn8.setPreferredSize(new Dimension(70, 60)); btn8.setBorder (BorderFactory.createRaisedSoftBevelBorder()) ; btn8.setFont(new Font("Sans Serif", Font.BOLD,20)); JButton btn9 = new JButton("="); btn9.addActionListener(ol); btn9.setBackground(new Color(0,128,255)); btn9.setBorder (BorderFactory.createEtchedBorder()) ; btn9.setPreferredSize(new Dimension(70, 60)); btn9.setFont(new Font("Sans Serif", Font.BOLD,20)); btn9.setToolTipText("calculate result"); JButton btn1 = new JButton("CE"); btn1.addActionListener(ol); btn1.setBackground(new Color(160,160,160)); btn1.setPreferredSize(new Dimension(50, 40)); btn1.setFont(new Font("Sans Serif", Font.BOLD,12)); btn1.setToolTipText("clear entry"); JButton btn2 = new JButton("C"); btn2.addActionListener(ol); btn2.setBackground(new Color(160,160,160)); btn2.setPreferredSize(new Dimension(50, 40)); btn2.setFont(new Font("Sans Serif", Font.BOLD,15)); btn2.setToolTipText("clear"); JButton btn3 = new JButton("/"); btn3.addActionListener(ol); btn3.setBackground(new Color(160,160,160)); btn3.setPreferredSize(new Dimension(50, 40)); btn3.setFont(new Font("Sans Serif", Font.BOLD,15)); btn3.setToolTipText("divide"); JButton btn4 = new JButton("*"); btn4.addActionListener(ol); btn4.setBackground(new Color(160,160,160)); btn4.setPreferredSize(new Dimension(50, 40)); btn4.setFont(new Font("Sans Serif", Font.BOLD,15)); btn4.setToolTipText("multiplie"); JButton btn5 = new JButton("-"); btn5.addActionListener(ol); btn5.setBackground(new Color(160,160,160)); btn5.setPreferredSize(new Dimension(50, 40)); btn5.setFont(new Font("Sans Serif", Font.BOLD,15)); btn5.setToolTipText("subtract"); JButton btn6 = new JButton("+"); btn6.addActionListener(ol); btn6.setBackground(new Color(160,160,160)); btn6.setPreferredSize(new Dimension(50, 40)); btn6.setFont(new Font("Sans Serif", Font.BOLD,15)); btn6.setToolTipText("add"); this.add(txtArea, BorderLayout.NORTH); this.add(panel,BorderLayout.CENTER); this.add(panel2,BorderLayout.EAST); panel.add(btn7); panel.add(btn8); panel.add(btn9); panel2.add(btn1); panel2.add(btn2); panel2.add(btn3); panel2.add(btn4); panel2.add(btn5); panel2.add(btn6); this.setJMenuBar(menuBar); this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); this.pack(); this.setResizable(false); this.setVisible(true); }}public class MyActionListener implements ActionListener { JTextArea area; public MyActionListener(JTextArea area){ this.area = area; } @Override public void actionPerformed(ActionEvent e) { JButton x = (JButton) e.getSource(); String y = x.getText(); String z = area.getText(); int v = area.getText().length(); int i = z.indexOf('.'); if(i==1 && "0".equals(area.getText())){ area.setText(""); } if(v<15){ if(i>=0&&".".equals(y)){ area.append(""); }else{ area.append(y); } }else{ Toolkit.getDefaultToolkit().beep(); } } }public class MyOperatorListener implements ActionListener { JTextArea area; double total; public MyOperatorListener(JTextArea area){ this.area = area; } @Override public void actionPerformed(ActionEvent e) { JButton x = (JButton) e.getSource(); String y = x.getText(); double calc = Double.parseDouble(area.getText()); switch(y){ case "+": total = total + calc; break; case "-": total = total - calc; break; case "*": total = total * calc; break; case "/": if(calc!=0){ total = total / calc; } break; default: break; } switch(y){ case "CE": calc = 0; area.setText("0"); break; case "C": total = 0; calc = 0; area.setText("0"); break; case "=": area.setText(Double.toString(total)); break; } }}
