what is profiling in java

What is OSGi?OSGi is also known as the dynamic modular system of the Java language , which defines an infrastructure for the development of modular applications. OSGi containers already have several open source implementations, such as Knoflerfish,Equinox , and Apache Felix. Through these containers, you can split your

Power node Java Training What is a Web container? Provides an environment for the application components (Jsp,servlet) in which the Jsp,servlet directly and the environment variables in the container are connected to each other without concern for other system problems. There are mainly Web servers to implement. For example: Tomcat,weblogic,websphere and so on. T

Brief The previous chapter briefly describes what a collection is and what kinds of collections there are.In this chapter we mainly introduce one of the implementation of collection, List.What is List In the previous chapter, we have learned that list is divided into 3 cate

Java garbage Collection Manual translation-What is garbage collectionAt first glance, garbage collection should do its name-find and throw away the rubbish. In fact, however, it does the opposite, garbage collection records all the objects that are still in use, and then marks the other as garbage. With this in mind, we started digging into the details of how mor

Q: What are processes and threads. A: The process is a collection of all threads, each of which is a path of execution in the process, and main is also a thread, and the primary thread. PS: Threads do not interfere with each other. Q: Why use multithreading. A: Improve the efficiency of the application, such as downl

assignment statement s= "" is a reference to a string type that points to another string (the value of the string is "", or an empty string).Common written Questions:New String ("ABC") has created several objects?Answer: one or two. Assuming that there is an "ABC" in the constant pool, then just create an object, assuming that there

Click to enter _ more _java thousand ask1. What is the difference between synchronous and asynchronous?In network programming, we often see synchronous, asynchronous, blocking, non-blocking, four calls and their combinations.Understanding blocking, non-blocking look here: [What is the difference between blocking and no

, the ticket will appear negativeThere is also a synchronization methodThe format is as follows:Synchronized method return type method name (parameter list) {}5, the life cycle of the thread/1) Create status2) Ready state3) Operating Status4) Blocking status5) Termination Status6, Add JS UnderstandingLook at a piece of code firstvar x = Document.getelementsbyname (data); var i; for (i = 0; i var value=x[i]

Java Comment Annotations x comment Note Difference x Comment Note Confusion Xjava comment Note Difference x note differs from comment xClick to enter _ more _java thousand ask1. What is the difference between annotations and annotations?See the comments here: what is the com

the core classes required by the Socketchannel approach: ServersocketchannelAn alternative class of serversocket that supports blocking and non-blocking communication. SocketchannelAn alternative class of sockets that supports blocking and non-blocking communication. SelectorReceive Client Connection readiness events for Serversocketchannel monitoring and connect server read-ready and write-ready events for socketchannel monitoring. SelectionkeyRepresents the handle to the

Java program startup parameter-D is used to do what? To inquire about the official explanation:Set a System property value. If Value is a string of contains spaces, you must enclose the string in double quotes:java-dfoo= "some string" SomeClassThat is,-D

numbers are converted to binary is also 1111 1111 1111 1111 1111 1111 1111 1111.So what does 1111 1111 1111 1111 1111 1111 1111 1111 mean?In fact:A memory is 32 consecutive 1, you put it according to an int to interpret is-1, according to unsigned int is 4294967295We can im

gives us a hidden danger. We should note that when object is null, the value of String.valueof (object) is the string "null", not null!!! remember to keep in mind when using the process. Imagine if we were to use if (string.valueof (object) ==null) {System.out.println ("the value passed in is null! ”);} Such a statement will likely be problematic. Think again, w

Click to enter _ more _java thousand ask1. What is Jconsole?Jconsole is a Java Program Performance Analyzer that can be run from the command line or in a terminal. can be used to monitor the performance of Java programs and tracking code.At the same time, a set of interfaces

Note that the path to the result is not the same as a point, because he resolves the "." and ".." The situation.A third example: (using: "D:\\test\\absolutetest.txt" absolute path)File File = new file ("D:\\test\\absolutetest.txt"); System.out.println (File.getpath ()); System.out.println (File.getabsolutepath ()); System.out.println (File.getcanonicalpath ()); Results: d:\test\absolutetest.txtd:\test\absolutetest.txtd:\test\ AbsoluteTest.txtConclus

, testing, does not affect the normal use of online projects, such as testing completed, and then on the production environment. ）-----------------------------------------------------------------------General company how to build Java development, testing, production environmentThe most used code hosting is SVN, the local development with Windows+eclipse, the production environment with Linux (that

Yesterday and a former colleague chatting, all kinds of spit slot PHP, Spit Groove swoole, he thinks PHP everywhere is a hole, PHP is very limited. Php+swoole is not suitable for high concurrent servers, C+swoole is the best solution. C + + has a variety of data structures, C + + can be thread, C + + can share objects.

Click to enter _ more _java thousand ask1. What is socketThe socket is also called a socket. The two applications on the network realize the exchange of data through a two-way communication connection, one end of the bidirectional link is called a socket, so the socket is pa

Click to enter _ more _java thousand ask1, Java.math package has what functionThe Java.math package provides a mathematical class in Java. Includes basic floating-point libraries, complex operations, and arbitrary-precision data operations. Main classes such as:?The classes in math are described below: arbitrary length shapingBigInteger, the arbitrary length of the non-variable shaping. Because the ba

Click to enter _ more _java FAQ-base Class Library1, Java.math package has what functionThe Java.math package provides a mathematical class in Java. Includes basic floating-point libraries, complex operations, and arbitrary-precision data operations. Main classes such as:?The classes in math are described below: arbitrary length shapingBigInteger, the arbitrary length of the non-variable shaping. Beca