Ant Import 和 Include的差異

http://ant.apache.org/manual/Tasks/include.html

其實官方網頁寫得很清楚了，貼一下原文

The short version: Use import if you intend to override a target, otherwise use include.
When using import the imported targets are available by up to two names. Their "normal" name without any prefix and potentially with a prefixed name (the value of the as attribute or the imported project's name attribute, if any).
When using include the included targets are only available in the prefixed form.
When using import, the imported target's depends attribute remains unchanged, i.e. it uses "normal" names and allows you to override targets in the dependency list.
When using include, the included targets cannot be overridden and their depends attributes are rewritten so that prefixed names are used. This allows writers of the included file to control which target is invoked as part of the dependencies.
It is possible to include the same file more than once by using different prefixes, it is not possible to import the same file more than once.

意思就是說如果被導入的target需要被 override的話就用import，不然用include即可。

例如官方的例子， 下面是要被導入的nested.xml

<project>
  <target name="setUp">
    <property name="prop" value="in nested.xml"/>
  </target>

  <target name="echo" depends="setUp">
    <echo>prop has the value ${prop}</echo>
  </target>
</project>

如果用import


<project default="test">
  <target name="setUp">
    <property name="prop" value="in importing"/>
  </target>

  <import file="nested.xml" as="nested"/>

  <target name="test" depends="nested.echo"/>
</project>


結果會是


setUp:

nested.echo:
     [echo] prop has the value in importing

test:
如果用include
<project default="test">
  <target name="setUp">
    <property name="prop" value="in importing"/>
  </target>

  <include file="nested.xml" as="nested"/>

  <target name="test" depends="nested.echo"/>
</project>


結果會變成

nested.setUp:

nested.echo:
     [echo] prop has the value in nested.xml

test:

結論: 如果沒有要改動到導入的XML東西用include即可，反之則用import

Java sleep(), yield()/join(), notify()/notifyAll()/wait() 用法差異

http://dylanxu.iteye.com/blog/1322066
太久沒有用到，最近要用到的時候又忘了...
乾脆把他整理一下。


1.sleep, yield, join 基本上都是Thread scheduling的method，sleep跟yield用法差不多，基本上就是Thread不需要執行的時候呼叫，只是差在sleep可以決定時間。

join則是等待某個Thread執行完，例如

                thread.join() //等thread跑完 在繼續

2.notify()/notifyAll()/wait() 則是Data Lock的部分，這些method都要在synchronized block中呼叫，不然會丟exception。

如果wait()的Thread要離開可以呼叫Thread的interrupt(); 會丟InterruptedException，可以跳離wait()狀態。

try {   
    while(true) {
        synchronized (this) {
            wait();
        }
    } 
} catch (InterruptedException e) {
    //interrupt triger
}