frequently asked questions in java

some bugs generated by the JVM, which will stop the program from running or produce incorrect results. Exception is a somewhat predictable error that can be captured and processed. In fact, error can also be captured ...18th, does list,set,map inherit from the collection interface?Collection sub-interfaces include Beancontext, Beancontextservices, BlockingqueueAlmost a Web page to be fooled, or Java Doc Comparative professional.19th, what is the diff

1. The difference between String and StringBufferThe Java platform provides two classes: string and StringBuffer, which can store and manipulate strings, That is, character data that contains more than one character. This string class provides values that cannot be changed strings and the strings provided by this StringBuffer class are modified when you know that character data is going to change, you can use StringBuffer typically, You can use Stri

rewrite the aof file, the performance impact of this persistence is minimal, but the aof file will continue to grow, aof file over the General Assembly to affect the recovery speed of master restart. Master should not do any persistent work, including memory snapshots and aof log files, in particular, do not enable memory snapshots to persist, if the data is more critical, a slave open aof backup data, the policy is synchronized once per second. Master calls bgrewriteaof rewrite aof file, a

into the corresponding method to invoke the logical layer of the method to achieve response to the customer.There are no doget, dopost, and so on in the Servlet interface and Genericservlet, these methods are defined in HttpServlet, but all return error information, so, each time we define a servlet, Must implement these methods such as Doget or Dopost.Each custom servlet must implement the Servlet interface, and the Servlet interface defines five methods, of which the more important three meth

Java's current heat has declined, but there are still a lot of people who learn java. Java's post is also a lot of infiltration. So, those classic Java knowledge points, you can see the problem can say 123? Come and have a look.The difference between 1.JDK and JRE What is the difference between 2.final, finally, and finalize?3. The difference between threads and processesHow does the HashMap in 4.

you need to get an ordered result you should use TREEMAP (the order of the elements in HashMap is not fixed).The collection framework provides two general map implementations: HashMap and TreeMap (TreeMap implements the SortedMap interface).HashMap is the best choice for inserting, deleting, and locating elements in a map. But if you want to traverse the key in natural order or in a custom order, TreeMap is better. The implementation of Hashcode () and Equals () is clearly defined by the key cl

. We can use this property to set the print report to another report, and the only difference to display the report is that the chart is a static picture. This can not only ensure that the dynamic effect of the statistical chart on the page, but also to ensure that the chart can be printed correctly.6. Sheet Report Group Implementation method:Detailed reference: http://blog.csdn.net/knowledgewang/article/details/63651157. Garbled problem:For details, please refer to the "Quick escape garbled" do

1.springMVC What are the ways to manage transactions2. Several ways to generate database IDsThe relationship between 3.heibirnate and Jpa,mybatis, IbatisWhat is the 4.hibernate caching mechanism?5.redius, Memercacha several common objects that implement caching6.JSF implementation Mechanism vs. JSPThe difference between a 7.hash map and a hash table8. Use of design patterns in projects9. Open source projects or tools used10. How hundreds of millions of users can implement storage (using Hadoop d

). The scheduler then reuses this thread for some and otherTask.What is the amount of memory that a task occupies in 9.Kilim?Here is a direct reference to the original text in the Kilim official document to answer:The amount of memory occupied by a task is:1. The Java object that represents the Task class2. If paused, an array of activation frames is stored. The KilimWeaver performs data flow and live variable and constant analysis(intra-procedurally)

). 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

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

state.Yield:yield is to discard the current CPU resources and give the CPU resources to other threads to use, but the time to discard is uncertain.JoinIn most cases, the main thread initiates a child thread, and if the child thread needs to complete a large number of complex operations, the main thread will end up before the child thread. However, if you need to use the result of a child thread after the child thread has finished running, you must use join in the main thread so that the main th

overlap? · Mike has $20 more than Todd. how much does each have given that combined they have $21 between them. you can't use fractions in the answer. (Hint: this is a trick question, pay close attention to the condition) · There are four dogs, each at the counter of a large square. each of the dogs begins chasing the dog clockwise from it. all of the dogs run at the same speed. all continously adjust their ction so that they are always heading straight towards their clockwise neighbor. how l

Summarize the common problems of PHPmailer group-sending Gmail, and phpmailer group-sending gmail. Summarize the frequently asked questions about PHPmailer group-sending Gmail. you may encounter many frequently asked questions whe

PHP 11 Most frequently asked questions and answers, PHP questions Are you looking for a PHP development job, and are you looking for some questions and answers about PHP? This article shares some of the 11 most frequently

TOMCAT7 and other high version, in fact, this is also a solution, and later.If we use the MAVEN plugin to develop, some people will use the jetty plug-in or the Tomcat plugin to deploy the application, if the deployment of the application has some problems, such as: we sometimes need to find in the Web container is not successful deployment, and so on, if the use of plug-ins at this time, it may be a bit inconvenient, It would be useful to have a myeclipse integrated tomcat environment, but the

use existing transactions that contain context-aware navigation (Context-aware navigation). Please refer to the documentation for more information. How do I debug an app in Eclipse? If you upgrade the ABAP Application Server system to SAP Kernel 7.21 (or higher), you can use the native ADT debugger. Otherwise, you have to use a GUI-based debugger. The Open Ecplise platform provides the best-in-Class extensibility points (extension points), how does ADT scale? Yes, SA

Active Directory Service Interface (ADSI): frequently asked Questions Microsoft Inc. What is ADSI? The Active Directory Service Interface (ADSI) is a class of open interfaces that extract directory services from different networks to provide a single view of network resource access and management. Regardless of which network environment contains these resources,