adroid中将mysql数据库中的数据读取到本地txt文件上时，出现数据库连接错误

package lyy.kev;

import java.io.InputStream;
import java.io.OutputStream;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;

import com.mysql.jdbc.Connection;
import com.mysql.jdbc.Statement;

import android.app.Activity;
import android.content.Context;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

public class File_Activity extends Activity {
    private EditText contentText;
    StringBuffer strb = new StringBuffer();
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        contentText = (EditText) this.findViewById(R.id.content);
        Button button = (Button) this.findViewById(R.id.button);
        Button button_read = (Button) this.findViewById(R.id.button_read);
        button.setOnClickListener(listener);
        button_read.setOnClickListener(listener);
       
        String url = "jdbc:mysql://localhost/kevin";
String user = "root";
String password="123456";
   try {
Class.forName("com.mysql.jdbc.Driver");
System.out.println("com.mysql normal");
} catch (ClassNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
try{
Connection conn;
conn =   (Connection) DriverManager.getConnection(url,user,password);
System.out.println( "DriverManager.getConnection");
Statement sql =   (Statement) conn.createStatement();
ResultSet rs = sql.executeQuery("select * from kevin");
while(rs.next()){
System.out.println(rs.getInt(1));
System.out.println(rs.getString(2));
}
conn.close();
sql.close();
rs.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
System.out.println( e);

}
    }
   private View.OnClickListener listener = new View.OnClickListener(){
        @Override
public void onClick(View v) {
        Button button = (Button) v;
        switch (button.getId()) {
case R.id.button:
int resId = R.string.success;
try {
OutputStream outSream = File_Activity.this.openFileOutput("kevin.txt",Context.MODE_PRIVATE);
strb();
    File_bean.save(outSream , strb.toString());
    //弹出提示
    Toast.makeText(File_Activity.this , resId, Toast.LENGTH_LONG).show();
} catch (Exception e) {
// TODO: handle exception
System.out.println("button"+e);
}
break;
case R.id.button_read:
try { 
   InputStream inSream = File_Activity.this.openFileInput("kevin.txt");
    String content = File_bean.read(inSream);
    contentText.setText(content);
    String[] result = content.split("/");
    for (String stri:result){
    System.out.println(stri);
    }
    Toast.makeText(File_Activity.this, "查看数据", Toast.LENGTH_LONG).show();
} catch (Exception e) {
// TODO Auto-generated catch block
// e.printStackTrace();
System.out.println("button_read"+e);
}
break;
}
        }    
   };
 

   public void strb(){
    int i = 1;
String str1="what is blue + yellow?";
String str2="green";
// while(i<3) {
strb.append("/"+"number of times is "+i+":"+str1+"/"+str2+"/");
// i++;
// }
    System.out.println("strb : ");
   }
}