電卓：８桁制限

package dentaku;

import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.math.BigDecimal;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTextField;

public class DentakuFrame extends JFrame {
    private static final long serialVersionUID = 1L;

    JPanel contentPane = new JPanel();
    BorderLayout borderLayout1 = new BorderLayout();

    JTextField result = new JTextField("");

    double stackedValue = 0.0;
    BigDecimal bd = new BigDecimal(stackedValue);
    boolean isStacked = false;
    boolean afterCalc = false;
    String currentOp = "";


    public DentakuFrame() {
        contentPane.setLayout(borderLayout1);
        this.setSize(new Dimension(300, 320));
        this.setTitle("電卓");
        this.setContentPane(contentPane);

        result.setHorizontalAlignment(JTextField.RIGHT);
        contentPane.add(result, BorderLayout.NORTH);

        JPanel keyPanel = new JPanel();
        keyPanel.setLayout(new GridLayout(4, 4));
        contentPane.add(keyPanel, BorderLayout.CENTER);

        keyPanel.add(new NumberButton("7"), 0);
        keyPanel.add(new NumberButton("8"), 1);
        keyPanel.add(new NumberButton("9"), 2);
        keyPanel.add(new CalcButton("＋"), 3);
        keyPanel.add(new NumberButton("4"), 4);
        keyPanel.add(new NumberButton("5"), 5);
        keyPanel.add(new NumberButton("6"), 6);
        keyPanel.add(new CalcButton("－"), 7);
        keyPanel.add(new NumberButton("1"), 8);
        keyPanel.add(new NumberButton("2"), 9);
        keyPanel.add(new NumberButton("3"), 10);
        keyPanel.add(new CalcButton("×"), 11);
        keyPanel.add(new NumberButton("0"), 12);
        keyPanel.add(new CalcButton("＝"), 13);
        keyPanel.add(new CalcButton("÷"), 14);
        keyPanel.add(new CalcButton(""), 15);

        contentPane.add(new ClearButton(), BorderLayout.SOUTH);
        this.setVisible(true);
    }


    public void appendResult(String c) {
        if (!afterCalc) {
            if (Integer.valueOf(result.getText() + c) <= 99999999) {
                result.setText(Integer.valueOf(result.getText() + c).toString());
            }
        } else {
            result.setText(c);
            afterCalc = false;
        }
    }


    public class NumberButton extends JButton implements ActionListener {
        private static final long serialVersionUID = 1L;

        public NumberButton(String keyTop) {
            super(keyTop);
            this.addActionListener(this);
        }

        public void actionPerformed(ActionEvent evt) {
            String keyNumber = this.getText();
            appendResult(keyNumber);
        }
    }

    public class CalcButton extends JButton implements ActionListener {
        private static final long serialVersionUID = 1L;

        public CalcButton(String op) {
            super(op);
            this.addActionListener(this);
        }

        public void actionPerformed(ActionEvent e) {
            if (isStacked) {
                double resultValue = (Double.valueOf(result.getText()))
                .doubleValue();

                if (currentOp.equals("＋"))
                    stackedValue += resultValue;
                else if (currentOp.equals("－"))
                    stackedValue -= resultValue;
                else if (currentOp.equals("×"))
                    stackedValue *= resultValue;
                else if (currentOp.equals("÷"))
                    stackedValue /= resultValue;

                if((int)stackedValue - stackedValue == 0){
                    result.setText(String.valueOf((int)stackedValue));
                }else{
                    result.setText(String.valueOf((int)Math.round(stackedValue)));
                }
            }
            currentOp = this.getText();
            stackedValue = (Double.valueOf(result.getText())).doubleValue();
            if(stackedValue > 99999999) {
                stackedValue = 99999999;
                result.setText(String.valueOf((int)stackedValue));
            }
            afterCalc = true;
            if (currentOp.equals("＝"))
                isStacked = false;
            else
                isStacked = true;
        }
    }

    public class ClearButton extends JButton implements ActionListener {

        private static final long serialVersionUID = 1L;

        public ClearButton() {
            super("C");
            this.addActionListener(this);
        }

        public void actionPerformed(ActionEvent evt) {
            stackedValue = 0.0;
            afterCalc = false;
            isStacked = false;
            result.setText("");
        }
    }
}