java performance tuning interview questions

Original link: http://ifeve.com/java-multi-threading-concurrency-interview-questions-with-answers/Multithreading and concurrency issues are among the questions that interviewers prefer to ask in a Java technology interview. Here,

be accessed throughout the class.The ② member variable is created as the object is built, disappears as the object disappears, and exists in the heap memory where the object resides.The ③ member variable has a default initialization value.Local variables:① Local variables are defined only within the local scope, such as within a function, within a statement, and only in the area to which they belong.② local variables exist in the stack memory, the scope of the action ends, and the variable spac

) 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

After JDK5, Java provides a more convenient security mechanism that uses lock locks for thread-locked operations and release operations without using synchronized . More clear. Example:Lock lock=new Reentrantlock ();Lock.lockCode that needs to be lockedLock.unlockWhy is lock more secure? Because synchronized may cause deadlock phenomenon, specifically about the deadlock phenomenon can refer to the operating system, there is no more to say.Summarize th

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

Multithreading and concurrency issues are among the questions that interviewers prefer to ask in a Java technology interview. Here, the most important questions are listed from the interview point of view, but you should still have a solid grasp of the basics of

Java custom generic interview questions: receive any array to reverse, java custom You can only operate on a certain type for reversal without using the generic type. The Code is as follows: package com.swift.fanxing;import org.junit.Test;public class RenyiReverse { @Test public void test() { int arr[]=new

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

monitor the connection pool found that only getting the connection did not release the connection operation, which appears to belong to 1. Due to the use of Eclipselink thought Entitymanager. Close () can release the connection, after reviewing the Eclipselink official documents, the original is improper use, the following is to obtain the connection details:Https://wiki.eclipse.org/EclipseLink/Examples/JPA/EMAPIJPA 2.0= Entitymanager.unwrap (java.sql.Connection. Class);... entitymanager.gettr

Today in a company (not disclosed) wrote a set of Java face questions. There is a question about this. Which design pattern used in Java.lang.Runtime? So what design pattern is used in the java.lang.Runtime? And what design patterns are used in java.utils.collection. At that time because of this unpopular knowledge not enough, and the API also read less, so a short answer. back home and searched the ne

to disk per secondKB_CCWR/S: The number of disk writes per second that the process is canceling (in kilobytes)Command: Pull up the commands corresponding to the processPidstat [-P PID]-R [-T] 1 3 display memory information650) this.width=650; "src=" Https://s3.51cto.com/wyfs02/M02/8E/AC/wKioL1jI4LPRFg3WAAAVeqTOCp8268.png "title=" _ 20170315143457.png "alt=" Wkiol1ji4lprfg3waaaveqtocp8268.png "/>MINFLT/S: The total number of minor page faults (no paging of memory pages from disk) per second for

to disk per secondKb_ccwr/s: the number of disk writes per second that the process is canceling (in kilobytes)Command: pull up the commands corresponding to the processpidstat [-p pid]-r [-t] 1 3 display memory information650) this.width=650; "src=" Https://s3.51cto.com/wyfs02/M02/8E/AC/wKioL1jI4LPRFg3WAAAVeqTOCp8268.png "title=" _ 20170315143457.png "alt=" wkiol1ji4lprfg3waaaveqtocp8268.png "/>Minflt/s: the total number of minor page faults (no paging of memory pages from Disk) per second for

create threads, how to create threads better (such as inheriting the thread class or calling the Runnable interface), and then gradually ask about concurrency problems like the Java memory model encountered in the process of Java concurrent programming, JDK1.5 introduces higher-order concurrency tools, common design patterns for concurrent programming, classic multithreading issues such as producer consume

Multithreading and concurrency issues are among the questions that interviewers prefer to ask in a Java technology interview. Here, the most important questions are listed from the interview point of view, but you should still have a solid grasp of the basics of

picture suffix 2, how to suffix is tampered with, then each file has a magic digital file upload-magic number5, the principle and implementation of Message Queuing Answer: 1, Message Queuing Principle 2, comprehensible message queue ActiveMQVi. Database Aspects1. 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,

 original link Connection author : Pankaj translator : Zheng Xudong proofreading : Fang FeiMultithreading and concurrency issues are among the questions that interviewers prefer to ask in a Java technology interview. Here, the most important questions are listed from the intervi