inforaveragejanpel.java

学生成绩管理系统

package myjava.javaSeries.java.compoent;
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import java.sql.*;
public class InforAverageJanpel extends JPanel
{
	private JLabel averagescore=new JLabel("Average");
    private JTextField JTscore=new JTextField(10);
    private JPanel JPlabels =new JPanel();
    private JPanel JPdisplay =new JPanel(); 
    float sum,average;
	public InforAverageJanpel()
	{
       try{
          InforModelDB mydata=new InforModelDB();
		  float[][] strTabelData=null;
		  String sqlst="select count(*) from students";
		  ResultSet rs =mydata.executeSelect(sqlst);
		  int Num=0;
		  if(rs.next())
			 Num=rs.getInt(1);
		  if(Num!=0)
		   {
		 rs=null;
		  strTabelData=new float [Num][1];
		  //形成Select语句
		 sqlst="select  * from students";
		 rs=mydata.executeSelect(sqlst);
		  int row=0;
		  while(rs.next())
		  {
           
			 strTabelData[row][0]=Float.parseFloat(rs.getString("score"));
			 row++;
		 }
          for(int i=0;i<row;i++)
           sum=sum+strTabelData[i][0];
           average=sum/Num;
          JTscore.setText(""+average);
          JTscore.setEnabled(false);
		  }else {JOptionPane.showMessageDialog(null,"the table has no record","about database",JOptionPane.INFORMATION_MESSAGE);}
	   }
		  catch(SQLException ex){
				ex.printStackTrace();
	  }catch(ClassNotFoundException ex){
				 ex.printStackTrace();
	  }
      JPlabels.add(averagescore);
      JPdisplay.add(JTscore);
      this.setLayout(new GridLayout(1,2));
      this.add(JPlabels);
	  this.add(JPdisplay);
	}
}