jdbc 不得不说的几句话

今天girlfriend到公司交作业(还是培训期),她们的pm让她们在数据读取的使用FOR循环(如例test1),问之,为啥,说pm说了,这样好,还拿了一本pm给的Effective Java,说看了就明白,废话不多说,看之,原来就这样一条,如果在循环体外不需要继续使用的变量建议使用FOR循环,并且在for的第一部分初始化,这样一来循环结束以后就会自动回收,但是大家仔细思考一下,这地方能利用这条原则??,RESULTSET
是跟着statement走的,当你关闭statement,resultset会被关闭,使你使用FOR循环没有任何好处,相反,WHILE要更快,使用for是弄巧成拙.例子如下,大家也看到while要比for快将近3倍,记录为1000条左右.写这个例子,希望大家不要犯类似的错.....
package jp.gibraltar.bnas.branch.accountclose.closecheck;

import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Vector;

import jp.gibraltar.util.DBUtil;
import junit.framework.TestCase;

/**
 * @author sfluo
 *
 * TODO To change the template for this generated type comment go to Window -
 * Preferences - Java - Code Style - Code Templates
 */
public class CloseCheckInputActionTest extends TestCase {

 public static void main(String[] args) {
  junit.textui.TestRunner.run(CloseCheckInputActionTest.class);
 }

 /*
  * @see TestCase#setUp()
  */
 protected void setUp() throws Exception {
  super.setUp();
 }

 /*
  * @see TestCase#tearDown()
  */
 protected void tearDown() throws Exception {
  super.tearDown();
 }

 public final void testExecuteCheckInput() {
  CloseCheckInputActionTest test = new CloseCheckInputActionTest();
  System.out.println(System.currentTimeMillis());
  test.test1();
  System.out.println(System.currentTimeMillis());
  test.test2();
  System.out.println(System.currentTimeMillis());
 }

 void test1() {

  Connection conn = DBUtil.getConnection();
  Vector vs = new Vector();

  try {
   Statement stmt = conn.createStatement();
   for (ResultSet rs = stmt
     .executeQuery("select * from accesslog_bnas "); rs.next();) {

    vs.add(rs.getString(1));

   }
   stmt.close();
   conn.close();
  }

  catch (SQLException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  }

 }

 void test2() {

  Connection conn = DBUtil.getConnection();
  Vector vs = new Vector();

  try {
   Statement stmt = conn.createStatement();
   ResultSet rs = stmt.executeQuery("select * from accesslog_bnas ");
   while (rs.next()) {
    vs.add(rs.getString(1));

   }

   stmt.close();
   conn.close();
  } catch (SQLException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  }

 }
}
print
1100141162919
1100141174035
1100141178942

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