frequently asked questions in java

Java Collections Interview QuestionsIn Java, collection interview questions is mostly asked by the interviewers. Here are the list of mostly asked collections interview questions with answers. 1) What is the difference betwe

code.17) Why wait, notify and notifyall These methods are not inside the thread class?This is a design-related issue that examines the interviewer's view of the existing system and some common but seemingly irrational things. To answer these questions, you need to explain why it makes sense to put these methods in the object class, and why not put them in the thread class. One obvious reason is that the locks provided by

50 Java Thread Surface questionsHere are some popular interview questions about Java threading, which you can use to prepare for the interview.1) What is a thread?A thread is the smallest unit that the operating system can perform operations on, which is included in the process and is the actual operating unit of the process. Programmers can use it for multiproce

In a typical Java interview, the interviewer asks the basic concepts of the thread, such as: why you need to use threads, how to create threads, and how to create threads better (for example, inheriting the thread class or calling the Runnable interface), And then gradually asked what concurrency problems were like in Java concurrency programming,

Multithreading and concurrency issues are an essential part of any Java interview.1) There are now three threads: T1, T2, and T3. How do you ensure that the T2 is executed after the T1 is complete and T3 executed after the T2 is complete?This threading issue is usually asked in the first stage or at the phone interview stage to determine whether you are familiar with the "Connect" method. This multithreadin

Beginners | questions For the problems in this series, everyone who learns Java should understand. Of course, it doesn't matter if you just learn to play Java. If you think you have gone beyond beginners, but do not understand these questions, please return yourself to the ranks of beginners. The content comes from CSD

1> How to locate an on-line service oom problem2>JVM GC roots exist in those places.3>mysql InnoDB How to do query optimization4>java the concept of CAsJava Services Oom, the more common reason is?? It is possible that the memory allocations are indeed too small, and the normal business uses a lot of memory such as the JMP-HEAP command to see the new belt, the old age memory size situation. See if the memory itself is allocated too small.?? An object

Packages(57) The concept of biased lock, lightweight lock, heavyweight lock, Spin lock1.5 JVM(+) Memory partitioning of the JVM runtime(59) example and cause of memory overflow oom and stack overflow SOE, how to troubleshoot and resolve(60) How to determine if an object can be recycled or survived(61) Common GC recovery algorithms and their meanings(62) Common JVM performance monitoring and Troubleshooting tool classes (JPS, Jstat, Jmap, Jinfo, Jconsole)() How the JVM sets parameters(+) JVM Per

Not accumulate Kuibu not even thousands of miles, here will continue to collect and update the Java Foundation related questions, currently has collected 100 questions.1. What is the B/s structure? What is the C/s architecture b/S (browser/server), browser/server program c/S (client/server), client/server, desktop applications 2. What do you kno

XML interview questions include XSLT techniques for transforming XML files, xpath,xquery, and XML basics such as DTDs or schemas. This article will see 10 common XML interview questions and answers. Most of these questions are asked in a Java interview and are also useful i

exclusive access to data during execution, so there are mechanisms to ensure that data is locked from being modified in the process, which is called locking mechanism.Hibernate supports two locking mechanisms: pessimistic and optimistic locking. Pessimistic lock, as the name implies pessimistic that in the process of data processing is very likely to have a change of the concurrent transactions (including the system's other transactions or transactions from the external system), so the processe

-depth message Queue Activemq Seven, the database aspect 1, the MySQL query field area is not case-sensitive? Answer: Do not differentiate, even if the value is not differentiated (I asked at the time, the area of the application of the size of the meaning of what, the interviewer did not say)2, simply say the database cluster and load balancing, distributed (I do not understand this piece) answer: Database load balancing and cluster reference, refere

-depth message Queue Activemq Seven, the database aspect 1, the MySQL query field area is not case-sensitive? Answer: Do not differentiate, even if the value is not differentiated (I asked at the time, the area of the application of the size of the meaning of what, the interviewer did not say)2, simply say the database cluster and load balancing, distributed (I do not understand this piece) answer: Database load balancing and cluster reference, refere

initialize.56, when writing the Clone () method, usually have a line of code, what is it?Answer: Clone has a default behavior, Super.clone (); He is responsible for generating the correct size of space and copying it bit by digit.57. How do I jump out of the current multiple nested loops in Java?Answer: use break; Return method.58, List, MAP, set three interfaces, access to elements, what are the characteristics of each?Answer: Lists hold elements in

More Java interview written paper series:Java interview written test stationHow does the 1.Java hashmap work?HashMap is a key value for the data structure, each key will have a corresponding value, the key is to identify such a value.HashMap based on the hashing principle, we store and retrieve objects through the put () and get () methods. When we pass a key-value pair to the put () method, it calls the Ha

to make the database efficiently find data.The commonly used data structure is b+tree, each leaf node not only holds the relevant information of the index key, but also increases the pointer to the neighboring leaf node, thus forming a b+tree with sequential access pointers, and the purpose of this optimization is to improve the performance of different interval accesses.When to use the index: Fields that often appear after the group By,order by and Distinc keywords Tables that are

wrapper type , which means that the wrapper type can be converted directly to the base data type , as shown in the following code:int m=100; Integer im=int N=im; The appeal code directly assigns m to the wrapper object IM, which is automatically boxed and then directly assigns the IM to the basic data type N, which is the automatic unpacking. Although the code on the surface is simple and convenient, however, in essence, the container still uses new to create the object, while unpacking is s

to avoid.Error indicates a system error and cannot be handled by the program.74. Does using log4j have any effect on the program?Yes, log4j is used for logging, logging some key sensitive information, usually logging to a local file or database. Recording in a local file, there are frequent IO operations that can consume some system resources. Logging in the database, the database tables are frequently manipulated, and have a certain impact on system

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

owns the lock gets the lock again, then the fetch counter increases by 1, and then the lock needs to be freed two times to get a true release. This mimics the semantics of synchronized; If a thread enters a synchronized block that is protected by a monitor that the thread already owns, it allows the thread to continue and does not release the lock when the thread exits the second (or subsequent) synchronized block. The lock is released only when the thread exits the first synchronized block tha