小第初学java，用java编了一个计算器，现将代码公布出来，希望各位大虾给于指点！

Question

class newListener implements ActionListener
        {
         public void actionPerformed(ActionEvent evt)
         {
         Object buttonpub=evt.getSource();
          
         if(buttonpub==buttonCe)            
         {
          flag=0;
                          jtf.setText("");
                          flag=0;
                          mi="0";
                          my="1";
                          j=1;
                          s=1;
                          k=1;
                          m=0;
                          h=0;
                      }
                     if(buttonpub==buttonDeng) 
                     {
                      me();
                      flag=0;
                     }
                     if  (buttonpub==button0)
                     {
                      if(m==1)
                      {
                      jtf.setText(" ");
                                 m=0;
                          }
                          k=1;
                          me="0";
                          mf=jtf.getText();
                          mh=mf+me;
                          jtf.setText(mh);
                          h=0;
                      }
                      if (buttonpub==button1)
                      {
                       x="1";
                       num(x);
                      }   
                      if (buttonpub==button2)
                      {
                       x="2";
                       num(x);
                      }
                      if (buttonpub==button3)
                      {
                       x="3";
                       num(x);
                      }                     
                      if (buttonpub==button4)
                      {
                       x="4";
                       num(x);
                      }
                      if (buttonpub==button5)
                      {
                       x="5";
                       num(x);
                      }  
                      if (buttonpub==button6)
                      {
                       x="6";
                       num(x);
                      }     
                      if (buttonpub==button7)
                      {
                       x="7";
                       num(x);
                      }  
                      if (buttonpub==button8)
                      {
                       x="8";
                       num(x);
                      }    
                      if (buttonpub==button9)
                      {
                       x="9";
                       num(x);
                      }     
                      if (buttonpub==button)
                      {
                       x=".";
                       num(x);
                      } 
                      if(buttonpub==buttonJian)  
                      {  
                       me();
                         sub();                  
                         flag=2; 
                       }
                       if(buttonpub==buttonJia)  
                      {  
                       me();
                         add();                  
                         flag=1; 
                       }
                       if(buttonpub==buttonCheng)  
                      {  
                       me();
                         mul();                  
                         flag=3; 
                       }
                       if(buttonpub==buttonChu)  
                      {  
                       me();
                         div();                  
                         flag=4; 
                       }
            }
     }
     public  void add()
     {
      m=1;
      mg=jtf.getText();
      float tempFloat=Float.parseFloat(mg);
      if(k==0)
      mi="0";
        float tempFloat1=Float.parseFloat(mi);
        tempFloat=tempFloat+tempFloat1;
        mi=mg;
        s=1;
        k=0;
        mAnswer=String.valueOf(tempFloat);
        jtf.setText(mAnswer);
     }
     public void sub()
      {                                           
           m=1;
           mg=jtf.getText();
           float tempFloat=Float.parseFloat(mg);
           if(k==0)
           {
               mi="0";
               s=1;
           }
           float tempFloat1=Float.parseFloat(mi);
           mi=mg;
           k=0;
           if(s==1)
           {               
             tempFloat=-tempFloat;
             s=0;
           }
           tempFloat=tempFloat1-tempFloat;
           mAnswer=String.valueOf(tempFloat);
           jtf.setText(mAnswer);
           }
        public void mul()
        {                                        
           m=1;
               mg=jtf.getText(); 
               float tempFloat=Float.parseFloat(mg); 
               if(k==0)
               my="1"; 
               float tempFloat1=Float.parseFloat(my); 
               tempFloat=tempFloat*tempFloat1;
               my=mg;        
               s=1; 
               k=0; 
               mAnswer=String.valueOf(tempFloat) ;
               jtf.setText(mAnswer);
        }
        public void div()
        {
         m=1; 
         mg=jtf.getText();
                float tempFloat=Float.parseFloat(mg);
               if(k==0)
             my="1";                    
             float tempFloat1=Float.parseFloat(my);
             if(flag==0)                    
             {
                    tempFloat1=Float.parseFloat("1");
                       tempFloat=tempFloat/tempFloat1;
             }   
             else            
              {
                      tempFloat=tempFloat1/tempFloat;
              }      
              my=mg;    
                 s=1;  
                 k=0;
              mAnswer=String.valueOf(tempFloat);
              jtf.setText(mAnswer);
         }
         public void me()
         {
          if(flag==1)
          {
          add();
          }
          else
          {
          if(flag==2)
          {
          sub();
          }
          else
          {
          if(flag==3)
          {
          mul();
          }
          else
          {
          if(flag==4)
          {
          div();
          }
          }
          }
          }
         }
         public void num(String y)
         {
          if(m==1)
          {
          jtf.setText(" ");
          m=0;
          }
          k=1;
          me=y;
          mf=jtf.getText();
          mh=mf+me;
          jtf.setText(mh);
          h=0;
         }
}

Answer 1

斗胆说几点：
1.Color里面的red、blue等应该是小写的字母；
2.小数点的个数没有考虑，可以多次出现；
3.除了加减乘除，其他功能好像都没有实现吧；
4.^_^