Scala / Java
摘要: DK1.5引入了新的类型——枚举。在 Java 中它虽然算个“小”功能，却给我的开发带来了“大”方便。
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摘要: 根据程序上下文环境，Java关键字final有“这是无法改变的”或者“终态的”含义，它可以修饰非抽象类、非抽象类成员方法和变量。你可能出于两种理解而需要阻止改变：设计或效率。
final类不能被继承，没有子类，final类中的方法默认是final的。 final方法不能被子类的方法覆盖，但可以被继承。 final成员变量表示常量，只能被赋值一次，赋值后值不再改变。 final不能用于修饰构造方法。 注意：父类的private成员方法是不能被子类方法覆盖的，因此private类型的方法默认是final类型的。
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摘要: cron is a UNIX tool that has been around for a long time, so its scheduling capabilities are powerful and proven. TheCronTrigger class is based on the scheduling capabilities of cron.
CronTrigger uses "cron expressions", which are able to create firing schedules such as: "At 8:00am every Monday through Friday" or "At 1:30am every last Friday of the month".
Cron expressions are powerful, but can be pretty confusing. This tutorial aims to take some of the mystery out of creating a cron exp
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摘要: jps类似linux的ps命令，不同的是ps是用来显示进程，而jps只显示java进程，准确的说是当前用户已启动的部分java进程信息，信息包括进程号和简短的进程command。
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摘要: Resource usage could prove critical at times for heavy-duty applications. Some famous Websites have shut down because of their inability to handle heavy loads. Most problems related to heavy loads can be handled, at a macro level, using clustering and load-balancing capabilities. Concerns remain at the application level with respect to excessive object creation and the availability of limited server resources like memory, CPU, threads, and database connections, which could represent potential bo
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摘要: Occurs when an exception is thrown in the contextInitialized method of a ServletContextListener
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摘要: When developing a https application, your test server often doesn't have a (valid) SSL certificate. This will cause the following exception to be thrown when connecting your client to the test server: "javax.net.ssl.SSLPeerUnverifiedException: peer not authenticated".
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摘要: Java 操纵对象都是通过引用来实现的，所有的对象变量都是所指向的对象的引用，那也就是说所有对象变量的值并不是它所指向的对象本身，而是该对象的引用，这句话听起来可能有点让人犯晕，举个例子来说，String str = new String("aaa"); 这条语句的意思是 new 了一个值为 "aaa" 的字符串对象，然后用一个名字叫 str 的对象变量来指向它，保存它的引用
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摘要: Log4j可以帮助调试（有时候debug是发挥不了作 用的）和分析，要下载和了解更详细的内容.
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摘要: AOP技术即（面向切面编程）技术是在面向对象编程基础上的发展，AOP技术是对所有对象或一类对象编程。核心是在不增加代码的基础上，还增加了新的功能。AOP编程在开发框架本身用的比较多，而实际项目中，用的比较少。它是将分散在各个业务逻辑代码中的相同代码抽取出来形成一个独立的模块。
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摘要: Need three artifacts to implement a JPA-compliant program:
An entity class
A persistence.xml file
A class through which you will insert, update, or find an entity
JPA is all about data persistence, so let's begin our examination of how it works with the data store design. Assume you have a CUSTOMER table, as in Table 1 below.
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摘要: The serialVersionUID is used as a version control in a Serializable class. If you do not explicitly declare a serialVersionUID, JVM will do it for you automatically, based on various aspects of your Serializable class, as described in the Java(TM) Object Serialization Specification.
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摘要: Executor就是Runnable和Callable的调度容器，Future就是对于具体的调度任务的执行结果进行查看，最为关键的是Future可以检查对应的任务是否已经完成，也可以阻塞在get方法上一直等待任务返回结果。Runnable和Callable的差别就是Runnable是没有结果可以返回的，就算是通过Future也看不到任务调度的结果的。
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