core java volume 2

byte[] B =New byte[3];//reading byte numbers, creating arraysRandomaccess.read (b, 1, 2);//read two bytes from pointer 1 write to array bString s =NewString (b);//Convert to StringSystem.out.println ("byte:" +s);//Output//Write FileFile file2 =NewFile ("C:\\img\\777.txt"); if(!File2.getparentfile (). exists ()) {File2.getparentfile (). Mkdirs (); } file2.createnewfile (); Randomaccessfile RandomAccess2

In fact, with the previous article "the prelude to learning DES encryption algorithms" as the basis, it is easy to implement the DES algorithm.However, I found the source code from the Internet, written in Java, and written in C ++, but all the code seems to be the same. Why is it the same? At the beginning, I wrote a class and added all the methods to the class. I guess it would be hard to implement it once if it wasn't the author's skill. In additio

I. Overview of new Java IOThe input and output streams in the Javaio are handled through byte movement, and the stream-oriented input-output system can handle only one byte at a time, so it is inefficient and the traditional input-output stream is blocked, meaning that when the data is unreadable, the current thread is blocked until it is read to a valid data to continue running.After java1.4, a series of improved input and output classes and methods

, the algorithm converts each character using 1-4-byte encoding.Code point/code unit (JDK 5.0) A code point is a code value (Unicode encoding) that corresponds to a character in an encoded table.In Java, the char type describes a code unit with UTF-16 encoding.UTF-16 uses a different length of encoding to represent all Unicode code points . In the basic multilingual plane, each character is represented by 16 bits (often referred to as a unit of

The more efficient Java threads have always been, and then know the efficiency of execution and CPU core number, today we tried the multi-core CPU under multithreading calculation: This machine i5 four cores, opens 1, 4, 10, 20, 40, 100, 400 threads to do 100W times respectively, the result is as follows: All tasks completed, total time consuming: 38368ms,thr

-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

"); } @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

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 mul

. 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

pointer exception when the value is unboxing if the key does not exist get returns nullint count = Counts.getordefault ("A", 0);//Recommended UseThe counter, when present, adds one:Counts.merge (Word, 1, integer::sum);If the word key does not exist before, connect Word with 1, or use the Integer::sum function to add 1 to the previous valueP243 Map Method! I didn't read it.1 // Iteration Map 2 for (map.entry entry:counts.entrySet ()) {3 String k =

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 * Gam

engine and metadata repository for object constraints. The framework that requires constraint definition, verification, and metadata (JavaEE or Java Se) bean validation specifications can be used to accomplish these functions. From the perspective of applications or infrastructure, this can avoid unnecessary repetitive work. Bean validation has been integrated into JSF 2.0 and JPA 2.0. In JSF, You can bind the form input field to the attribute of the

, 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

child class is placed in the parent class object, and only methods of the parent class can be called. 1 Employee empl = new Manager () 2 Empl.setbonus (100); // compile error, no Setbonus method in parent class 3 4 // You can convert a parent class reference to a subclass reference 5 if (empl instanceof Manager) { Span style= "color: #008080;" >6 Manager Mgr = (manager) Empl; 7 Mgr.setbonus (100 8 } When a method is declared final,

Well known in. NET, the key generated by the RSA class is in XML format, while other languages such as Java generally use the PKCS8 format key, JavaScript generally uses the PKCS1 format. We in the development process is likely to encounter the need to interface with other languages developed API, if we encounter RSA encryption and decryption, we must ensure that key is the same, in order to ensure the correct processing of data, we definitely need to

= 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

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

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

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

In Java, every variable, constant is a type.variables :Example: int i;Double A;1 The variable name must be a sequence of alphanumeric characters beginning with a letter. But unlike most programming languages, the range of letters and numbers in Java is larger, and the letters include ' a ' ~ ' Z ', ' a ' ~ ' Z ', ' _ ' or any Unicode character that represents a letter in any language, such as Chinese: decla