今天girlfriend到公司交作業(還是培訓期),她們的pm讓她們在數據讀取的使用FOR循環(如例test1),問之,為啥,說pm說了,這樣好,還拿了一本pm給的Effective java,說看了就明白,廢話不多說,看之,原來就這樣一條,假如在循環體外不需要繼續使用的變量建議使用FOR循環,并且在for的第一部分初始化,這樣一來循環結束以后就會自動回收,但是大家仔細思考一下,這地方能利用這條原則??,RESULTSET
是跟著statement走的,當你關閉statement,resultset會被關閉,使你使用FOR循環沒有任何好處,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快將近3倍,記錄為1000條左右.寫這個例子,希望大家不要犯類似的錯.....
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 ");