core java programming interview questions

A basic data structureMust be included in the classMust have public static Main methodCase sensitiveIi. Types of dataFour types of integers:INT 4 byte short 2 byte Long8 byte byte1 byteTwo floating-point typesFloat 4 bytesDouleble 8 bytesChar Type, Boolean typeConstants use the final definition class constants using the static final definitionThird, Operation symbolsX!=0 1/x>x+y//If x=0, do not perform the calculation behind avoid x=0 1/x operationMathematical operation symbol MATH.PI, etc.Iv.

This chapter highlights:Runnable describes a task that can be executed asynchronouslyExecutor to include runnable instances in the execution planCallable describes a task that produces resultsYou can submit one or more callable instances to executorservice, and when these callable have execution results, merge the resultsWhen multiple threads manipulate shared data without synchronization, the result is unpredictableParallel algorithms and thread-safe data structures are better than

1. Generic Programming generic programming means that the code you write can be reused by many different types of objects. For example, you do not want to design separate classes for aggregating string and integer objects. (I think this is what I'm saying here.) Create an object that can be of type string and integer. But have the same behavior or attributes) The code is as follows: Public class stringt

50 Classic Java Programming questions (directory)Title from: http://blog.sina.com.cn/s/blog_60fafdda0100wb21.html "Program 1" Testrabbit.javaTitle: Classical Questions: There are a pair of rabbits, from the 3rd month after birth a pair of rabbits each month, the rabbit long to the third month after the birth o

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things at once to further improve performance. The Java Virtual Machine (JVM) itself is the reason for the widespread use of multithreading technology. This article will discuss creating multithreaded Java code and some of the best practices for concurrent programming, as well as some tools and resources that are extremely useful to developers. It is not possib

Executorservice= Executors.newfixedthreadpool (2); for(inti = 0; I ) {Runnable Runnable=NewRunnable () {@Override Public voidrun () {LongTime = (Long) (Math.random () *1000); System.out.println ("Rest Time:" +time+ "MS"); Try{thread.sleep (time); } Catch(interruptedexception e) {e.printstacktrace (); } } }; Executorservice.execute (runnable); } executorservice.shutdown (); }}Note: 1. The thread pool must be closed using the shutdown display.2. In

( This. Time); } Catch(interruptedexception e) {e.printstacktrace (); } } } Public Static voidMain (string[] args) {TreadTest2 threadTest2=NewTREADTEST2 (3000, "004"); TreadTest2 treadTest22=NewTreadTest2 (2000, "125"); NewThread (ThreadTest2). Start (); NewThread (treadTest22). Start (); }}3. Select the thread class or the Runable interface?1. If you just want to rewrite the runable interface instead of overriding the thread other methods, use the Runable interface.2. If a subcla

As a business developer, there are few technologies that can be used at work. Although usually always say what, multi-threading, concurrency, injection, Attack! But in practical work, these things are not necessarily used. Because the framework we used has already done that.For example, web development, there are a lot of requests coming in, supposedly, we should consider concurrency problems. But in fact, Spring receives the request, after assigning to the controller, it is already thread-safe,

method.can also be displayed at the time of the call to write1 Public Static void int int j); 2 Arrays.3. Type limitThe type parameters of a generic class or method need to meet certain requirements, or you need to be able to invoke some common methods . You can qualify the type.T extends AutocloseableType parameters can have multiple qualifications: T extends Runnable autocloseable※ Multiple interfaces can be qualified, but only one of them is a class. If a qualification is a class, it must

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=NewRandomaccessfile (File2, "RWD");//Accessi

Feedback on issues with the 2017 object-oriented Programming (JAVA) section on nine-week learning summary1. Blog not written by: Gao Shuping Gao Junmei Fong Mau Wang Ruiqiang Zong Peng Li Xianglong Ma Lun Mitch Mao Provencale--The number of students who do not submit the blog in time is on the rise, please think about the value of Java Learning Blog, and some of

4.1. Introduction to object-oriented programmingobject-oriented Programming, or OOP for short, was the dominant programming paradigm these days, having replaced T He "structured," procedural programming techniques that were developed in the 1970s. Since Java is object-oriented, and you had to be familiar with the OOP t

: Use node stream as input or output. The filter stream is created using an existing input stream or an output stream connection.6. Java SOCKET Programming, read the server several characters, and then write to the local display. After the client sends a connection request to the server, it passively waits for the server to respond.A typical TCP client is going through the following three steps:1. Create a

The book is generally finished, but the seventh chapter is not in a hurry to end.But fortunately it is finished, barely count it.Recall this year, quite feeling, the heart has been seeking progress, but it is very difficult to act up.Think about it indeed ah, want to always progress must sacrifice their spare time, although not to exclude learning, but you have to admit that the feeling of paralysis is very good.Man, there's really nothing to stop, and once you get down, you're probably going to

letter I in the string; intn =0; for(intA =0; A if(' I '= = Str[a]) {n++; }} System. out. println ("(2) The number of occurrences of the letter I in the string:"+ N); System. out. println ("\ n");//(3) Remove substring "my";System. out. println ("(3) Remove substring" my "); System. out. println (S1.substring (S1.indexof ("My"), S1.indexof ("My") +"My". Length ())); System. out. println ("\ n");//(4) converts this string into an array of strings, requiring each array eleme

Synchronization block for wait is not run until the 1,notify sync block is finished2,interrupt () is not a static method, there will be interuptexception on the wait thread, and the lock will be released.3,notify () Wake-up thread is random, did not know what to wake up, learned that notify is an object, which is locked with the relevant object, will unlock which4,object.wait (5000) No notify during the period, they will automatically wake upJava multithreaded

1,timer timer = new Timer (true) is now the daemon2,timer is in accordance with the Shun, no asynchronous3,timer method, Schedule (timertask task, Date firsttime, long Perid) Perid is the repetition delay, firsttime in advance is executed immediately after the start4, the time of the line range sleep is counted in the perid inside, will not recalculate5,timertask method, Canel cancel your task6,timer method, Canel cancel your task7, when the Cancel method is called externally, it is sometimes no

, and Proxyselector represents a proxy selector, which is an abstract class. A program can implement its own proxy selector by inheriting it, and the following two abstract methods need to be implemented:ListConnectfailed (URI uri,socketaddress sa,ioexception IoE): This method is invoked when a connection proxy fails.After implementing its own proxy selector, a static method called Proxyselector in the program SetDefault () registers the proxy selector.The static method called Proxyselector Getd

; } public String GetClassID () {return classID; } public void Setclassid (String classID) {this.classid=classid; }}Complement:Studentpxgit log:Programming problem Code Hosting(Results of program operation)(1) Use the stack structure to output several items of an, where an=2an-1+2an-2,a1=3,a2=8(2) write a program to store student English scores in a list in a tree set so that they are automatically sorted by program and output sorted results(3) There are 10 USB drives, there are two import