what is elasticsearch in java

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

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

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

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

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

1. Using the class defined below, what is the output of the following code?Output Result:Please summarize the rules of Java field initialization according to the output of the code . There are two places in Java initialization: initialization blocks and constructors, where initialization

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 a stringThe Java.lang.String class represents a string that is usually bright, so-called string, which is a set of characters composed of character sets. It has the following characteristics:String is an immutable objectEach

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

What is the difference between return and return null in Java?The biggest difference:ReturnThe return value of the method must be void!return null;The return value of the method must not be the original data type (the wrapper class has been removed) and the void!Return is the way to jump out ...Return null also jumps o

, 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

When we do development, often have the URI and URL confused problem, if at that time directly look at the URI and URL source code can not be confused. First I summarize the relationship between URI and URL: Their relationship is: The URL is a special URI, is the URI including the URL,What exactly

The following error is reported when starting:Workaround:Go to the following directory: wlntio.dll and paste it into the C:\Java\bin directory (assuming the JDK was previously installed to C:\Java); However, in fact, my directory is only the folder 32, there is no x64, t

industry with more frameworks: Dubbo, Zookeeper, Netty, Mycat and so on.That's what I thought for the moment. In fact, more should write their own projects, such as writing a more complete personal blog, in the process, encounter problems try to search the current more popular technology to solve, so you will learn faster than light reading.Talk about the front-end, in fact, the current domestic front-end is