spring interview questions and answers for experienced in java

, the next () method of the iterator throws a Concurrentmodificationexception exception.Concurrent containers support concurrent traversal and concurrent updates.The main classes are Concurrenthashmap, copyonwritearraylist and Copyonwritearrayset, read this article to understand How to avoid concurrentmodificationexception.8. What is the Executors class?Executors provides some tool methods for the Executor,executorservice,scheduledexecutorservice,threadfactory and callable classes.Executors can

keep the original base implementation. We can just inherit from it and rewrite the methods we need. Read the Java futuretask example to learn how to use it.7. What is the implementation of concurrent containers?Java collection classes are fast failures, which means that when a collection is changed and a thread iterates through the collection using Iterators, the next () method of the iterator throws a Con

solves this problem for us. After the online pool submits the callable task, a future object is returned, using which we can know the status of the callable task and get the result of the execution callable returned. The future provides a get () method so that we can wait for callable to end and get its execution results.Read this article to learn more about the callable,future example. 6. What is Futuretask?Futuretask is a fundamental implementation of the future, and we can use it with execut

class hello{public static void Main (string[] ARS) {A ab = new B (); Executed here, results: 1a2bAB = new B (); Executed here, results: 1a2b2b}}A: the output is 1a2b2b; the static code snippet for a class can be thought of as code executed by the class for the first load (virtual machine load), and for class loading, the first thing to do is to execute the construction of its base class, and then perform its own construction.50, the Succession time class execution order question, generally is t

class redefined the same method in the parent class. The Override method must have a method name, a parameter list, and a return type that are identical. The Override method does not restrict access to the original method.does 6.Java support multiple inheritance? Java does not support multiple inheritance, and each class allows only one class to be inherited, but multiple interfaces can be implemented.7. W

choose an array instead of a ArrayList. If we want to traverse a map in order of insertion, we need to use TreeMap. If we don't want to repeat, we should use set.(2) Some collection classes allow you to specify the initial capacity, so if we can estimate the number of stored elements, we could use it to avoid re-hashing or resizing.(3) programming based on interfaces, rather than implementation-based programming, allows us to easily change the implementation later.(4) Always use type-safe gener

type as needed. For example, if you specify a size, we will choose an array instead of a ArrayList. If we want to traverse a map in order of insertion, we need to use TreeMap. If we don't want to repeat, we should use set.(2) Some collection classes allow you to specify the initial capacity, so if we can estimate the number of stored elements, we could use it to avoid re-hashing or resizing.(3) programming based on interfaces, rather than implementation-based programming, allows us to easily ch

). In the process of populating the handler, depending on your configuration, Spring will do some extra work for you: Httpmessageconveter: Converts the request message (such as Json, XML, and so on) to an object, converting the object to the specified response information. Data Transformation: Data conversion for a request message. such as string conversion to Integer, double, and so on. Data is initialized: Data is formatted for the request message. such as converting a string into a formatt

article to learn more about the callable,future example.6. What is Futuretask?Futuretask is a fundamental implementation of the future, and we can use it with executors to handle asynchronous tasks. Usually we do not need to use the Futuretask class, it becomes very useful when we intend to rewrite some methods of the future interface and keep the original base implementation. We can just inherit from it and rewrite the methods we need. Read the Java

) Select the correct collection type as needed. For example, if you specify a size, we will choose an array instead of a ArrayList. If we want to traverse a map in order of insertion, we need to use TreeMap. If we don't want to repeat, we should use set.(2) Some collection classes allow you to specify the initial capacity, so if we can estimate the number of stored elements, we could use it to avoid re-hashing or resizing.(3) programming based on interfaces, rather than implementation-based prog

TreeMap. If we don't want to repeat, we should use set.(2) Some collection classes allow you to specify the initial capacity, so if we can estimate the number of stored elements, we could use it to avoid re-hashing or resizing.(3) programming based on interfaces, rather than implementation-based programming, allows us to easily change the implementation later.(4) Always use type-safe generics to avoid classcastexception at run time.(5) Using the immutable classes provided by the JDK as key to t

corresponding action, while the user's data to fill the corresponding actionform, and then the Actionform is distributed to action for processing.3.Action automatically calls the Excute method, in which the action takes the user-filled data from the Actionform and invokes the model (JavaBean) for processing, and then displays the results of the processing in a different view (JSP page)struts-config.xml:struts 's configuration file .It says that each user's request is handled and forwarded throu

most cases, we only need to determine if the values are equal, and then compare them with the Equals method.There is also a equalsignorecase that can be used to ignore case comparisons. String s1 = "abc"; String s2 = "abc"; String s3= new String("abc"); System.out.println("s1 == s2 ? "+(s1==s2)); //true System.out.println("s1 == s3 ? "+(s1==s3)); //false System.out.println("s1 equals s3 ? "+(s1.equals(s3))); //true12. What is a string pool?As the name i

equalsignorecase that can be used to ignore case comparisons."ABC"; "abc"; String ("abc"); System.out.println (//true System.out.println (//false System.out.println (//true 12. What is a string pool?As the name implies, a string constant pool is used to store strings. It exists in the Java heap memory.Explains how a string pool exists in Java heap space and when we use different ways to cr

after the real object is called.Proxy mode,The proxy class and the proxy class implement the same interfaceAn instance of a proxy class in a proxy classBehavioral patterns: Focus on communication between objectsSuch as: Responsibility chain mode, iterator mode, command modeResponsibility chain ModelSimilar interceptors, etc.Command mode:Separates callers from Callee's behaviorInterpreter mode:Each syntax is an interpreter classIterator mode:Change the collection class's view traversal and add a

example, a landing page, using the PO mode, will create a LoginPage class, the class will define the user name input box, password input box, login button webelenentFor the corresponding element to implement the corresponding method, the input box is used to input, you need to create a user name and enter the password method, so that the real page consistent, so the design concept is PO mode. The pagefactory belongs to the PO mode, which is used to initialize the page Class of each PO pattern i

to Wangwei"$ Java-jar Blockchain-java-jar-with-dependencies.jar-add "Send 3.5 BTC to Wangwei"Print Blockchain$ Java-jar Blockchain-java-jar-with-dependencies.jar-printSummarizeIn this article we implement the Blockchain storage function, next we will implement the address, transaction, wallet, some of the functions of

? What is Futuretask? How to wake up a blocked thread? How do immutable objects help with multithreading? What does multi-threaded context switching mean? What thread scheduling algorithms are used in Java? What is the role of Thread.Sleep (0)? What is the Java memory model, which areas are thread-shared, and which are unshared What are optimistic and pessimistic locks? Why do I synchroniz

solves this problem for us. After the online pool submits the callable task, a future object is returned, using which we can know the status of the callable task and get the result of the execution callable returned. The future provides a get () method so that we can wait for callable to end and get its execution results.What is Futuretask?Futuretask is a fundamental implementation of the future, and we can use it with executors to handle asynchronous tasks. Usually we do not need to use the Fu

. TreeSetthe largest and smallest elements can be obtained from. Summary: Collections.sort() provides a list that is sorted once. PriorityQueueand TreeSet Dynamic maintenance of the ordered collection.9. Copy ListThere are two ways to copy a list. One is to use a ArrayList constructor. 1 ArrayListnewArrayList The other is to use Collections.copy() . 12 ArrayListnewArrayListCollections.copy(dstList, srcList); It is important to