java code snippets for practice

The synchronized keyword provided by Java provides thread-synchronous access to critical sections. Because it is difficult to synchronized basedThe synchronization code is written correctly, and the Concurrency tool class provides an advanced Synchronizer. Countdown latch (countdown latch), Sync screen(cyclic barrier), switch (exchanger), Semaphore (semaphore), and Phaser Synchronizer. The following mainInt

-based method or temporal table method, you should first look for a set-based solution to solve the problem, and the set-based approach is generally more efficient.22. Try to avoid large transaction operation and improve the system concurrency ability.23. Try to avoid the return of large data to the client, if the amount of data is too large, should consider whether the corresponding demand is reasonable.By doing Itoo from V1.0 To V3.0, plus the previous project, in fact, when doing SQL optimiza

[Java concurrent programming practice] -- "J. U. C": Condition, j. u. ccondition Before reading Condition, let's take a look at the following example: Factory type, used to store and retrieve goods: Public class Depot {private int depotSize; // repository size private Lock lock; // exclusive lock public Depot () {depotSize = 0; Lock = new ReentrantLock ();} /*** warehouse receiving ** @ param value */public

Doublebalance; PublicBank (Doublebalance) { Super(); This. Balance =balance; } Public DoubleGetBalance () {returnbalance; } Public voidSetbalance (Doublebalance) { This. Balance =balance; } DoubleWithDrawal (DoubleDamount)throwsException {if(damount>balance) { Throw Newinsufficientfundsexception (); } if(damount) { Throw Newnagativefundsexception (); } return This. Balance; } Public Static voidMain (string[] args) {Bank

Java practice of 04JavaWeb-03 session technology, java04javaweb-03I. Introduction to session Technology 1. What is session? Why is session technology required? Session: the process from opening a browser, accessing a website, to closing the browser is called a session. The http protocol is in the status.2. Classification of session Technology Client Storage Technology: Cookie Server storage technology: Sess

) { inti = 0, J = 0; while(i Rightarray.length) {if(leftarray[i] >=rightarray[j]) Array[start+ +] = leftarray[i++]; ElseArray[start+ +] = rightarray[j++]; } while(i ]; while(j ]; } public voidPrintresult (int[] array,int[] [] Query) { int[] result =New int[query.length]; for(inti = 0;i ) { int[] Temparray =New int[array.length];//this gets the cloned object of the array, requiring the address to be Changed. If you assign a value directly, the two addre

7.Reverse IntegerThe idea of solving problems: Using code that enforces type conversions, first using long, then judging values and then forcing them into int1 Public classSolution {2 Public intReverseintx) {3 LongReverse_n =0;4 while(X! =0) {5Reverse_n = Reverse_n *Ten+ x%Ten;//Key Code6x = x/Ten;7 }8 if(Reverse_n > Integer.max_value | | Reverse_n integer.min_value) {9 return 0;Ten } One

PrivateRabbittemplate rabbittemplate; Public void SendCall(String content) { for(inti =1; I 3; i++) {LongExpiration = i * the; String message = i +"-"+ content; System. out.println(String. Format("Sender:%s", message)); Rabbittemplate.Convertandsend(Mqconstant.Delay_call_ttl, (Object) message,New Expirationmessagepostprocessor(expiration)); } }}Server:@Componentpublic class Server { @Async @RabbitHandler @RabbitListener(queues = MQConstant.CALL) public void callProcess(String

Exercise 1: (1) Create a class in a package that creates an instance of the class outside the package where the class is located.Import Mil.oms.main.test.Test; Public class maintest {public static void Main (String args[]) { Test test=new test (); } /** Run result test () instantiation ... Package Mil.oms.main.test;public class Test{public Test () {System.out.println ("Test () instantiation ...");}Exercise 2: (1) rewrite the

Frame1_jbutton2_actionadapter (this)); Jlabel2.settext ("First off: 10"); Jlabel2.setbounds (New Rectangle (414, 473, 171, 21)); Contentpane.add (JPANEL1); Contentpane.add (JButton2); Contentpane.add (JButton1); Contentpane.add (JSlider1); Contentpane.add (JLABEL1); Contentpane.add (JLABEL2); This.addkeylistener (New MyListener ()); Jbutton1.addkeylistener (Ne

= Executors.newcachedthreadpool (); listOutput Result:Threading 1 is runningthreading 2 are runningthreading 3 is Runningresult:1result:3java.util.concurrent.cancellationexce PtionAll Future.isdone () are true after Executorservice#invokeall () is executed, and when Future.get () takes the result, the future that is timed out is thrown cancellationexception. Because the Future#cancel () method is called inside InvokeAll.The source code is as follows:

, removes the last element from the container in the method body and joins the consumer. Examples of use are: carcontainerIf you have another setThe method Pop (setOur idea is that the pop receives the parameter application is "E of some kind of superclass set", through the "and Super keyword combined use just can achieve this purpose, namely setThird edition public void pop (setAfter the modification, setWith the use of the extends or Super keyword on the method parameters, you get th

interface is deserialized, the class's constructor with no arguments is called first, which is different from the default deserialization method. A Java.io.InvalidException:no valid constructor exception is thrown if the class's constructor with no parameters is removed, or the access permission for the constructor is set to private, default, or protected level.Four Serialization compatibility for different versions of serializable classesAny class that implements the Serializable interface has

....A functional interface using Java* In Kotlin you can pass a lambda instead of a traditional anonymous class in Java to do the argument* The way you can work with Lambda instead of a Java anonymous class is because there is only one abstract method in the ActionListener interface. (Runnable, callable)* This interface is called a functional interface, or Sam i

Concurrenthashmap is part of Doug Lea's Util.concurrent package, which offers a higher degree of concurrency than Hashtable or synchronizedmap. Also, for most successful get () operations, it tries to avoid a complete lock, and the result is a very good throughput for concurrent applications. This month, Briangoetz carefully analyzed the code of the Concurrenthashmap and explored how Doug Lea achieved such a remarkable result without losing thread saf

more high-level code on the call stack needs to process the interrupt after the irrevocable task ends. Listing 6 shows a method that waits for a blocking queue until an available item appears in the queue, regardless of whether it is interrupted or not. For the convenience of others, it restores the interrupt state in a finally block after it has ended, lest it deprive the caller of the interrupt request of the right. (It cannot restore the interrupt

Currently there is no uniform definition of thread safety, and the author summarizes a definition as follows:This class is thread-safe when multiple threads access a class, regardless of how the runtime environment is scheduled or how those threads will be executed alternately, and if no additional synchronization or coordination is required in the keynote code, and the class is able to behave correctly.In concurrent programming, a situation in which

(!compareandset (prev, next)); return prev; }Public final Boolean compareandset (int expect, int update) { Return Unsafe.compareandswapint (this, valueoffset, expect, update);}Among them, Compareandswap is the abbreviation of CAs. Returns True if Prev and next are not equal. Otherwise, returns false. Finally, it is done through unsafe.The code above indicates that if Compareandset returns True, the while condition is false, exiting the l

hidden from the constraint. This means that only the overlay method will be dynamically bound, and the shadowing will not occur dynamically. In Java, all other methods, except the static method and the final method, are dynamically bound. As a result, the above output will appear.SummarizeThe constructor invocation of the parent class and the initialization process must precede the child classThe order of initialization is also in accordance with; Ob

Frame1_jbutton2_actionadapter (this)); Jlabel2.settext ("First off: 10"); Jlabel2.setbounds (New Rectangle (414, 473, 171, 21)); Contentpane.add (JPANEL1); Contentpane.add (JButton2); Contentpane.add (JButton1); Contentpane.add (JSlider1); Contentpane.add (JLABEL1); Contentpane.add (JLABEL2); This.addkeylistener (New MyListener ()); Jbutton1.addkeylistener (Ne