core java volume 2

A core feature of the Bean Validation (JSR 303)--java EE 6, which defines a metadata model and API for entity validation. Its default metadata source is annotations, but developers can extend it through an XML descriptor. The Validation API does not rely on a particular application layer or programming model, so that the same set of validations can be shared by all tiers of the application. It also provides

Scala, inheriting a base class is similar to Java, with a two-point limit, and (1) Overriding the method requires the Override keyword, (2) only the primary constructor can pass parameters to the base class constructor. Markerfactory is a single case, once the definition is complete, its name represents the only instance of the singleton object, and the singleton can be passed to the function as if it we

references cannot exist independently and are always converted to instances of a functional interfaceYou can use this and the super parameter in a method referenceThis::equals equivalent to X->this,equals (x)3.5 constructor ReferenceA constructor reference is similar to a method reference, except that the method name is new. For example, Person::new is a reference to the person constructor. Which constructor is called depends on the context.You can establish a constructor reference with an arra

Category: Java technology 2009-08-29 01:03 213 people read reviews (0) favorite report JavaapiswingxmlioJava's core API is very large, which gives developers a lot of convenience, often people have comments, Java makes programmers become silly.But some of the content I think must be mastered, otherwise it can not be skilled use of

atomic classprivate final Atomicinteger ctl = new Atomicinteger (Ctlof (RUNNING, 0)); thread pool model core parameters corepoolsize: The minimum number of surviving worker threads (if set allowcorethreadtimeout, then the value is 0) maximumpoolsize: Maximum number of threads, Limited to capacity keepalivetime: the duration of the corresponding thread, the time unit specified by Timeunit workqueue: Task Force column that sto

small task. is not much like map/reduce.Fork/join mode has its own scope of application. If an application can be decomposed into multiple subtasks, and the result of combining multiple sub-tasks is able to get the final answer, then this application is suitable to be solved with Fork/join mode. Forkjoin is the recursive decomposition of a problem into sub-problems, and then the sub-problem parallel operation after merging results. Let's use the next Fork/join framework with a simple requiremen

The problem of this blog cannot be solved. It is just an analysis and speculation. Some subsequent actions may prove some guesses and may not solve anything. If you have any questions in the same situation as me, please kindly advise. Problem: Last weekend, I went out to outing with my colleagues and managed my children at home. I went to the production environment and observed the current running status of the cluster machines. I found that the pressure on these multi-

Java core technology: an in-depth understanding of abstract classes and interfaces1. General description Abstract classTemplate Method ModeInterface2 abstract class Abstract classes are classes that cannot be instantiated. They are generally designed to inherit from quilt classes to implement abstract methods of parent classes.The biggest difference from a common class is that it cannot be instantiated. You

The ArrayList of the Core Java thing.　　High-rise ground, Java Foundation to pick up. Today, I looked at the core Java from the basic point to find a little bit to share.First of all, the professional-level Lucky Star actor---employee Class (PS: I am focused on Lucky Star 30)

Multicore CPUs are now the mainstream. Using multi-core technology, can effectively play the ability of hardware, improve throughput, for Java programs, can implement concurrent garbage collection. However, the use of multi-core technology in Java also brings some problems, mainly because of multi-threaded shared memor

establishment of i+1Analysis: Suppose i is of type int , when the value range (overflow) of type int is exceeded after i+1 , at this time i+1 will become negative, obviously negative positivethe data type of the 8.0.123 is (double)Analysis:0.123 Of course is double ,0.123f or 0.123F is Float9. Which of the following is the character-oriented output stream (A)A.bufferedwriterB.fileinputstreamC.objectinputstreamD.inputstreamreader Analysis: java

/gravity/southeast7. Does the existence of I make The establishment of i+1Analysis: If i is of type int , when the value range (overflow) of type int is exceeded after i+1 . At this point the i+1 becomes negative, obviously negative positivethe data type of the 8.0.123 is (double)Analysis:0.123 is of course double . 0.123f or 0.123F is float9. Which of the following is a character-oriented output stream (A)A.bufferedwriterB.fileinputstreamC.objectinputstreamD.inputstreamreader Analysis:

Common Java core Notes * The keyword static is used for static variables and static methods, that is, to design it in two scenarios: one is to allocate a single bucket for a specific domain, do not consider the number of objects to be created, or even create objects. Second, a method is not associated with any objects in its class, that is, it can be called without creating an object.* The final keyword ind

) return type does not require (can be same or different)Advantage: External users often do not pay attention to the method of invocation, by the compiler's own judgmentCreating and Initializing objects---------------------------Created object: New Student ();1) to open up space for the object;2) default initialization for member variables of an object (0/false/null)3) Explicit initializationClass student{String name= "Zhan";int age=23;}Cons: Each tim

is to ensure the uniqueness of the class name.Import of Class 7.1A class can use all the classes in the owning package, as well as the public classes in other packages.You can only import a package using an asterisk (*), and you cannot import all packages prefixed with Java using Import java.* or import java.*.*.It is possible to add a specific package name to r

/dopost-destroy destroy)The difference between > and CGI is that the servlet is in a server process, it runs its service methods in a multithreaded manner, an instance can serve multiple requests, and its instances are generally not destroyed, and CGI generates a new process for each request, which is destroyed after the service is completed. So the efficiency is lower than the servlet.(servlet: Server process, multithreaded run service, one instance service multiple requests, not normally destr

I recently concluded that I have not improved my skills. I am ready to start training. Write down this and give myself a goal. The core APIs of Java are very large, which makes it very convenient for developers. Many people often comment that java makes programmers stupid.However, I think some content must be mastered. Otherwise, it will be difficult to use

Thread pool is a key point to be mastered in multi-threaded learning.The cost of starting a new thread is higher because it involves interacting with the operating system. In this scenario, using the thread pool can improve performance, especially if you need to consider using a thread pool when you want to create a lot of short-lived threads in your program.I. How do I create a thread pool??Before Java5, the thread pool was developed manually, and from Java5 onwards,

time.Look directly at an example:public class program{static void Main (string[] args) { UI layer = new UI (); Layer. Setdataaccessor (New Xmldataaccessor ()); Layer. Do (); }} class ui{dataaccessor m_accessor; public void Setdataaccessor (Dataaccessor accessor) {m_accessor = accessor;} public void does () { m_accessor. GetUser (); }} interface dataaccessor{void GetUser (); void RegisterUser ();} class xmldataaccessor:dataaccessor{public void GetUser () {} public void RegisterUser () {}}Th

Exception handlingThe parent class in the exception structure Throwable class, its Exceptionlei class and the error class. What we can catch in the program is the subclass exception of exception.Error at System level: Error in Java Runtime Environment, we are not controllable.Exception is a program-level error: we can control it. 1) catch Exceptions in two ways: one is to add Try-catch to catch the exception, and the other is to declare the exceptio