用java编写计算的代码，有点晕，求指教

下面是我在网上搜的一个gui的计算器代码，可是我发现不是编写者，就是理解作者本人某些变量的含义啊
我想成员变量deng,fu,i,point,n,equ都分别代表了什么？package Four;
import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
@SuppressWarnings("serial")
public class T11 extends JFrame implements ActionListener{
    int deng=0,fu=0,i=0,point=0,n=0;
    float sum=0,equ;
    String v="";
    BorderLayout bo=new BorderLayout();
    GridLayout g=new GridLayout(4,4);
    JPanel jp=new JPanel();
    JTextField jt=new JTextField(" 0");
    JButton b1=new JButton("7");
    JButton b2=new JButton("8");
    JButton b3=new JButton("9");
    JButton b4=new JButton("+");
    JButton b5=new JButton("4");
    JButton b6=new JButton("5");
    JButton b7=new JButton("6");
    JButton b8=new JButton("-");
    JButton b9=new JButton("1");
    JButton b10=new JButton("2");
    JButton b11=new JButton("3");
    JButton b12=new JButton("*");
    JButton b13=new JButton("0");
    JButton b14=new JButton(".");
    JButton b15=new JButton("=");
    JButton b16=new JButton("/");
    @SuppressWarnings("static-access")
    public T11(String title)
    {
        super(title);
        this.setSize(300,300);
        jp.setSize(300,200);
        jt.setSize(300,100);
        jp.setLayout(g);        jp.add(b1);
        jp.add(b2);
        jp.add(b3);
        jp.add(b4);
        jp.add(b5);
        jp.add(b6);
        jp.add(b7);
        jp.add(b8);
        jp.add(b9);
        jp.add(b10);
        jp.add(b11);
        jp.add(b12);
        jp.add(b13);
        jp.add(b14);
        jp.add(b15);
        jp.add(b16);        b1.addActionListener(this);
        b2.addActionListener(this);
        b3.addActionListener(this);
        b4.addActionListener(this);
        b5.addActionListener(this);
        b6.addActionListener(this);
        b7.addActionListener(this);
        b8.addActionListener(this);
        b9.addActionListener(this);
        b10.addActionListener(this);
        b11.addActionListener(this);
        b12.addActionListener(this);
        b13.addActionListener(this);
        b14.addActionListener(this);
        b15.addActionListener(this);
        b16.addActionListener(this);
        this.add(jt,bo.NORTH);
        this.add(jp,bo.CENTER);
        this.setLocationRelativeTo(null);        
        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        this.setVisible(true);
    }
    public void actionPerformed(ActionEvent e)
    {
        if(e.getSource()==b1)
        {
            if(deng==1||fu==1)
                v="";
            v=v+"7";
            jt.setText(v);
            deng=0;fu=0;n=1;
        }
        if(e.getSource()==b2)
        {
            if(deng==1||fu==1)
                v="";
            v=v+"8";
            jt.setText(v);
            deng=0;fu=0;n=1;
        }
        if(e.getSource()==b3)
        {
            if(deng==1||fu==1)
                v="";
            v=v+"9";
            jt.setText(v);
            deng=0;fu=0;n=1;
        }
        if(e.getSource()==b4)//+
        {
            if(n==1)
            {
                if(i==0)
                    sum=Float.parseFloat(v);
                else if(i==1){sum+=Float.parseFloat(v);}
                else if(i==2){sum-=Float.parseFloat(v);}
                else if(i==3){sum*=Float.parseFloat(v);}
                else if(i==4){sum/=Float.parseFloat(v);}
            }
            else
            {
            }
            i=1;
            fu=1;n=0;deng=0;point=0;        }
        if(e.getSource()==b5)
        {
            if(deng==1||fu==1)
                v="";
            v=v+"4";
            jt.setText(v);
            deng=0;fu=0;n=1;
        }
        if(e.getSource()==b6)
        {
            if(deng==1||fu==1)
                v="";
            v=v+"5";
            jt.setText(v);
            deng=0;fu=0;n=1;
        }
        if(e.getSource()==b7)
        {
            if(deng==1||fu==1)
                v="";
            v=v+"6";
            jt.setText(v);
            deng=0;fu=0;n=1;
        }
        if(e.getSource()==b8)//-
        {
            if(n==1)
            {
                if(i==0)
                    sum=Float.parseFloat(v);
                else if(i==1)sum+=Float.parseFloat(v);
                else if(i==2)sum-=Float.parseFloat(v);
                else if(i==3)sum*=Float.parseFloat(v);
                else if(i==4)sum/=Float.parseFloat(v);
            }
            else
            {
            }
            i=2;
            fu=1;n=0;deng=0;point=0;        }
        if(e.getSource()==b9)
        {
            if(deng==1||fu==1)
                v="";
            v=v+"1";
            jt.setText(v);
            deng=0;fu=0;n=1;
        }
        if(e.getSource()==b10)
        {
            if(deng==1||fu==1)
                v="";
            v=v+"2";
            jt.setText(v);
            deng=0;fu=0;n=1;
        }
        if(e.getSource()==b11)
        {
            if(deng==1||fu==1)
                v="";
            v=v+"3";
            jt.setText(v);
            deng=0;fu=0;n=1;
        }        // ioe_gaoyong添加
        if(e.getSource()==b12)//-
        {
            if(n==1)
            {
                if(i==0)
                    sum=Float.parseFloat(v);
                else if(i==1)sum+=Float.parseFloat(v);
                else if(i==2)sum-=Float.parseFloat(v);
                else if(i==3)sum*=Float.parseFloat(v);
                else if(i==4)sum/=Float.parseFloat(v);
            }
            else
            {
            }
            i=3;
            fu=1;n=0;deng=0;point=0;        }   // ioe_gaoyong添加结束        if(e.getSource()==b4)//*
        {
            if(n==1)
            {
                if(i==0)
                    sum=Float.parseFloat(v);
                else if(i==1)sum+=Float.parseFloat(v);
                else if(i==2)sum-=Float.parseFloat(v);
                else if(i==3)sum*=Float.parseFloat(v);
                else if(i==4)sum/=Float.parseFloat(v);
            }
            else
            {
            }
            i=1;//这里修改
            fu=1;n=0;deng=0;point=0;        }        if(e.getSource()==b13)
        {
            if(deng==1||fu==1)
                v="";
            v=v+"0";
            jt.setText(v);
            deng=0;fu=0;n=1;
        }
        if(e.getSource()==b14)//.
        {
            if(deng==1||fu==1)
                v="";
            if("".equals(v))jt.setText("0.");
            else
            {
                v=v+".";
                jt.setText(v);
            }
            point=1;
            deng=0;fu=0;n=1;        }
        if(e.getSource()==b15)//=
        {
            if(fu==1){}
            else
            {
                switch(i)
                {
                    case 0: equ=sum;break;
                    case 1: equ=sum+Float.parseFloat(v);break;
                    case 2: equ=sum-Float.parseFloat(v);break;
                    case 3: equ=sum*Float.parseFloat(v);break;
                    case 4: equ=sum/Float.parseFloat(v);break;
                }
                sum=0;v="";
                v=String.valueOf(equ);
                jt.setText(String.valueOf(equ));
                deng=1;i=0;            }
        }
        if(e.getSource()==b16)//+
        {
            if(n==1)
            {
                if(i==0)
                    sum=Float.parseFloat(v);
                else if(i==1)sum+=Float.parseFloat(v);
                else if(i==2)sum-=Float.parseFloat(v);
                else if(i==3)sum*=Float.parseFloat(v);
                else if(i==4)sum/=Float.parseFloat(v);
            }else{
            }
            i=4;
            fu=1;n=0;deng=0;point=0;        }
    }
    public static void main(String[]args){
        new T11("计算器");
    }
}