Java Programming Tricks 1

1、计算时间

 

       long StartTime = System.currentTimeMillis(); // 取出目前時間

// ==============================
// 你的程式
// ==============================

long ProcessTime = System.currentTimeMillis() - StartTime; // 計算處理時間

 

 

2、线程休眠

 

       try {

       Thread.sleep(500);

} catch (InterruptedException e) { }

 

 

3、生成随机数

 

       int randomNumber=(int)(Math.random()*８)+1；

 

 

4、Runtime.getRuntime( ).exec( ) 的运用

 

（1）打开本地文件

public class OpenFile {

    public static void main(String[] args) {

        String path = "c:/temp/SW.txt";

        try{

            Runtime.getRuntime().exec("cmd /c start "+path);

        }catch(Exception e) {

           

        }

    }

}

（2）运行.bat文件

public class RunBat {

    public RunBat (String cmdline) {

        try{

            Process p = Runtime.getRuntime().exec(cmdline);

        }catch(Exception e) {

        }

    }

    public static void main(String[] args) {

        new RunBat("c:/temp/test.bat");

    }

}

（3）运行exe 文件

public class OpenFile {

    public static void main(String[] args) {

        try{

            Runtime.getRuntime().exec("c:/temp/WinRAR.exe");

        }catch(Exception e){

        }

    }

}

 

 

 

5、HashMap 用法

 

private static final String FUND_KEY = "fund";

private static final String SUB_KEY = "subaccount";

 

HashMap resultMap = new HashMap(2);

List mrFunds = new ArrayList();

List mrSubaccts = new ArrayList();

resultMap.put(FUND_KEY, mrFunds);

resultMap.put(SUB_KEY, mrSubaccts);

return resultMap;

 

HashMap mrAccts = getSelectedChildrenForMRGroup(groups);

List mrFunds = (List)mrAccts.get(FUND_KEY);

List mrSubacctouns = (List)mrAccts.get(SUB_KEY);

 

6、Log

 

public void save_old(AddClient addClient) {

              log.debug("execting AddClient");

              try {

                     getHibernateTemplate().save(addClient);

                     log.debug("AddClient successful");

              } catch (RuntimeException re) {

                     log.error("AddClient failed", re);

                     throw re;

              }

       }