求助，一个计算器的括号功能怎么写啊。

import javax.swing.*;

import javax.swing.event.*;

import java.awt.*;

import java.awt.event.*;

public class computer1 extends JFrame implements ActionListener{

Double r1,r2,total,c1,c2;

int i,j,j1=10,j2=7,c;

JButton[] Button1,Button2;

String str1=new String();

String str2=new String();

String str=new String();

String strr=new String();

boolean flag=true;

Container cp;

JLabel output=new JLabel("输出");

JTextField outarea=new JTextField(10);

JButton Button3=new JButton("=");

JButton clear=new JButton("清除");

JButton exit=new JButton("退出");

JMenuBar menubar=new JMenuBar();

JMenu now =new JMenu("文件(F)");

JMenu edit=new JMenu("编辑(E)");

JMenu help=new JMenu("帮助(H)");

JMenu format=new JMenu("格式(O)");

JMenuItem properties=new JMenuItem("属性",'P');

JMenuItem editer=new JMenuItem("退出",'X');

JMenuItem naw =new JMenuItem("新建",'N');

JMenuItem open=new JMenuItem("打开",'O');

JMenuItem paste=new JMenuItem("复制",'C');

JMenuItem cut=new JMenuItem("剪切",'X');

JMenuItem delet=new JMenuItem("删除",'D');

JMenuItem Auok=new JMenuItem("自动换行",'W');

JMenuItem font=new JMenuItem("字体",'F');

JMenuItem about=new JMenuItem("关于..",'A');

public computer1(){

super("祥祥的简单的计算器");

super.setJMenuBar(menubar);

setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

setSize(300,300);

now .add(naw);naw.setEnabled(false);

now.add(open);open.setEnabled(false);

now.add(properties); properties.setEnabled(false);

now.add(editer); editer.addActionListener(new exit());

edit.add(paste); paste.setEnabled(false);

edit.add(cut);cut.setEnabled(false);

edit.add(delet);delet.setEnabled(false);

format.add(Auok);Auok.setEnabled(false);

format.add(font);font.setEnabled(false);

help.add(about);about.addActionListener(new message());

now.setMnemonic('F');

edit.setMnemonic('E');

format.setMnemonic('F');

help.setMnemonic('H');

menubar.add(now);

menubar.add(edit);

menubar.add(format);

menubar.add(help);

BorderLayout layout1=new BorderLayout();

GridLayout layout2=new GridLayout(4,4,6,6);

cp=getContentPane();

JPanel panel1=new JPanel(new GridLayout(2,1));

panel1.add(output);

panel1.add(outarea);

cp.add("North",panel1);

JPanel panel2=new JPanel(layout2);

Button1=new JButton[j1];

Button2=new JButton[j2];

Button2[2]=new JButton("*");

Button2[3]=new JButton("%");

Button2[4]=new JButton("(");

Button2[5]=new JButton(")");

Button1[1]=new JButton("1");

Button1[2]=new JButton("2");

Button1[3]=new JButton("3");

Button2[0]=new JButton("+");

Button1[4]=new JButton("4");

Button1[5]=new JButton("5");

Button1[6]=new JButton("6");

Button2[1]=new JButton("-");

Button1[7]=new JButton("7");

Button1[8]=new JButton("8");

Button1[9]=new JButton("9");

Button1[0]= new JButton("0");

for (i=0 ;i<10;i++) {

panel2.add(Button1[i]);

Button1[i].addActionListener(this);

};

for (j=0 ;j<6;j++) {

panel2.add(Button2[j]);

Button2[j].addActionListener(new operation());

};

Button3=new JButton("=");

JPanel panel3=new JPanel(new GridLayout());

panel3.add(Button3);

panel3.add(clear);

panel3.add(exit);

cp.add("Center",panel2);

cp.add("South",panel3);

Button3.addActionListener(this);

clear.addActionListener(this);

exit.addActionListener(new exit());

}

public void clear(){

this.total=0.0 ;

this.str=this.str1=" ";

this.str1=" ";

this.str2=" ";

outarea.setText(" ");

flag=true;

}

class exit implements ActionListener{

public void actionPerformed(ActionEvent e)

{System.exit(0);}

}

public void actionPerformed(ActionEvent e){

for(i=0;i<10;i++){

if(e.getSource()==Button1[i]){

if(flag){

str=str.valueOf(i);

str1+=str;

outarea.setText(str1);

r1=Double.parseDouble(str1);

}

else{

str=str.valueOf(i);

str2+=str;

outarea.setText(str2);

r2=Double.parseDouble(str2);

}

}

}

if(e.getSource()==clear) clear();

if(e.getSource()==Button3){

total=0.00;

switch(c){

case 0:total=r1+r2;outarea.setText(strr.valueOf(total));strr=strr.valueOf(total);break;

case 1:total=r1-r2;outarea.setText(strr.valueOf(total));strr=strr.valueOf(total);break;

case 2:total=r1*r2;outarea.setText(strr.valueOf(total));strr=strr.valueOf(total);break;

case 3:total=r1/r2;outarea.setText(strr.valueOf(total));strr=strr.valueOf(total);break;

}

}

}

class operation implements ActionListener{

public void actionPerformed(ActionEvent a){

for(j=0;j<4;j++)

if(a.getSource()==Button2[j]){

c=j;

char aa[ ]=new char[4];

aa[0]='+';aa[1]='-';aa[2]='*';aa[3]='/';

str=str.valueOf(aa[j]);

outarea.setText(str);

flag=false;

}

}

}

class message extends JFrame implements ActionListener{

public void actionPerformed(ActionEvent e){

JFrame frame=new JFrame("信息...");

frame.setSize(60,250);

frame.getContentPane().setLayout(new FlowLayout());

frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

frame.setVisible(true);

JLabel label1=new JLabel("关于作者信息：" );

JLabel label2=new JLabel("祥。");

frame.getContentPane().add(label1);

frame.getContentPane().add(label2);

}

}

public static void main(String[] args){

computer1 fr= new computer1();

fr.setVisible(true);

fr.pack();

}

}

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我就是实现不了括号功能，请同道友人指点一下，谢谢。

还有我觉得我的计算器还有一些不好的地方，请大家指点一下。修正一下。