core java certification

1. three main features of the process:Independence: With its own independent address space, a process cannot directly access the address space of other processes.Dynamic: is a collection of instructions that are active in a system.Concurrency: A single process can be performed concurrently on multiple processors, with no impact on each other.2. Differences in concurrency and parallelism:Parallel is the same time, there are multiple instructions on multiple processors at the same time, concurrenc

Java core --- AnnotationAnnotation is a new feature in jdk 5 and later versions. Spring and Hibernate frameworks provide annotation configuration methods. This article describes the annotations in the middle of the wave breeze and mainly explains the usage of jdk built-in annotations, the declaration and definition of annotations, as well as the usage of custom annotations are at the beginning, to say a lit

PublicFirsrtactor () { - This. Init (); - } - Private voidinit () { +Texture=NewTexture ("Badlogic.jpg"); - } + @Override A Public voidDraw (Batch batch,floatParentalpha) { atBatch.draw (texture,0,0); - } - -}1 PackageCom.mygdx.useactor;2 3 ImportCom.badlogic.gdx.ApplicationAdapter;4 ImportCom.badlogic.gdx.Gdx;5 Importcom.badlogic.gdx.graphics.GL20;6 ImportCom.badlogic.gdx.graphics.g2d.SpriteBatch;7 /**8 * Game main class, using actors9 * @authorJack (L

-generated Catch blockE.printstacktrace (); } }}4. Use Ruturn to stop the thread Public classMyThreadextendsThread {@Override Public voidrun () { while(true) { if( This. isinterrupted ()) {System.out.println ("Stop it!"); return; } System.out.println ("Timer=" +System.currenttimemillis ()); } } Public Static voidMain (string[] args)throwsinterruptedexception {MyThread T=NewMyThread (); T.start (); Thread.Sleep (2000); T.interrupt (); }}Results:Two(1) Advantages

= new MyThread1 (); Thread1.setpriority ( 1 = new MyThread2 (); Thread2.setpriority ( 10The result: high-priority threads are always executed mostly first, run faster, and do not mean that the thread's priority is independent of the order in which the threads are executed. This results in a 10 times-fold difference in priority. Change to a similar priority then look, like.Third, thread priority has randomnessMultiple runs of code with similar priority, you will find t

"); } @Override Public voidsleep () {System.out.println ("Puppy" +name+ "in Bed"); } @Override Public voidintroduce () {System.out.println ("Dog:color:" +color+ ", Age:" +age+ ", Name" +name+ ", type:" +type); } @Override PublicString toString () {return"Dog's name:" +name+ ", age; +age+ "years old, Kind" +type+ ", Color:" +color; }}//Cat Class Public classCatextendsanimal{String name; String sex; @Override Public voideat () {System.out.println ("Cat Eats fish"); } @Override Public voidsleep

Document directory Environment Problem Solution Environment JBoss 6.0 + myeclipse 8.6 + MySQL 5.1 + Struts 2.3 + EJB 3.0 Problem The following exception occurs when JBoss is started: Java. Lang. noclassdeffounderror: ORG/hornetq/API/CORE/client/clientsession Solution Check whether the struts jar package version is correct. My EJB project uses jar files such: @ Wentasy blog

Bean validation (JSR 303) -- JavaEEA core feature of 6, which defines a metadata model and API for entity verification. The default metadata source is annotation, but developers can extend it through the XML descriptor.The validation API does not rely on a specific application layer or programming model, so that the same set of verification can be shared by all layers of the application. It also providesAPI to increase the mechanism of custom verifica

First of all, the concurrent class library should be a very important class library in java. When building some Synchronous Code, containers, and concurrency, you can find ready-made and usable classes in this class library... The most core type in this class library is the AbstractQueuedSynchronizer type. You can implement your own synchronization tools based on it. For example, the ReentrantLock type is a

. According to the function of the Division: node flow and packaging flow.four basic streams : Byte input stream, byte output stream, character output stream, character input stream BYTE stream Character Stream Output stream OutputStream Writer Input stream InputStream Reader The four basic streams are abstract classes : The other flows are inherited from the four main classes.We cannot create four base stre

Merge stream/Sequential stream (Sequenceinputstream):is to combine multiple input streams into a single Stream object.1 Public classSequenceinputstreamdemo {2 Public Static voidMain (string[] args)throwsException {3 //To create a sequential stream object4Sequenceinputstream in =NewSequenceinputstream (NewFileInputStream ("Stream.txt"),5 NewFileInputStream ("Stream2.txt"));6 7 byte[] buffer =New byte[1024];8 intLen =-1;9 while(len = in.read (

Memory Stream (Array stream):The data is temporarily present in the array and will be retrieved from the array later.1. Byte memory stream: Bytearrayinputstream/bytearrayoutputstream2. Character Memory stream: Chararrayinputstream/chararrayoutputstream3. String stream: Stringreader/stringwriter (storing data in an array)BYTE memory stream: Public classBytearraydemo { Public Static voidMain (java.lang.string[] args)throwsException {//byte array output stream: program-to-memoryBytearrayoutputstrea

, Len)); - } -Bin.close ();}BufferedWriter and BufferedReader Public Static voidMain (string[] args)throwsIOException {//OutputBufferedWriter out =NewBufferedWriter (NewFileWriter ("Stream.txt",true)); Out.write ("Hoe wo Day Copse"); Out.newline ();//line BreakOut.write ("Sweat wo xia tu"); Out.close (); //inputBufferedReader in =NewBufferedReader (NewFileReader ("Stream.txt")); Char[] buffer =New Char[1024]; intLen =-1; while(len = in.read (buffer))!=-1) {System.out.println (New

/wkiom1vpxdli6rvtaac6ccqzdhe717.jpg "width=" 648 "height=" 481 "alt=" wkiom1vpxdli6rvtaac6ccqzdhe717.jpg "/ > 2. StringBuilder, StringBuffer classWe have learned from the string class that it is an immutable object, so the creation of new objects is thrown whenever the content is modified. So when we have a need to frequently modify the string, this does not only not reduce the memory overhead, the return will increase the memory overhead. To this end