Java

In the log analysis, the recorded SQL is often analyzed, so a full line of SQL format, multi-line shrinkage is very necessary, many database clients provide SQL formatting capabilities, but complex multi-layered nested SQL often formatted L is not

Click to enter _ more _java thousand ask1, meta-annotation is whatSee the comments here: what is the commentUnderstanding custom Annotations See here: How to customize annotationsMeta annotations are responsible for annotating other annotations.

Installation of JDK: Download, install Configuring Environment variables A) path:.; %java_home%\bin;b) installation directory for JAVA_HOME:JDKc) classpathJDK and JRE and JVM:JAVA program run Process: Compiling Javac:

calling private methods with reflection, accessing private propertiesWith reflection, the first is the acquisition of the class object, followed by the method and the Field object.In the case of method, you can see from the documentation:The

The atomic class provided by Java is implemented by Sun based on CAs, which is an optimistic lock. About optimistic lock and pessimistic lock.The atomic variable class is equivalent to a generalized volatile variable that supports both atomic and

the difference between Java NIO and blocking I/O1. Blocking I/O communication modelIf you have a certain understanding of blocking I/O now, we know that blocking I/O is blocked when the Inputstream.read () method is called, and it waits until the

Click to enter _ more _java thousand ask color= "#ff0000"1. How to customize annotationsTo learn to use annotations, we need to understand annotations and understand common annotations provided by Java. More importantly, learn to customize

Class, superclass, sub-class:The subclass method cannot directly access the private domain of the superclass.This and Super are not references and cannot be assigned to another object variable. Super in the constructor of the application:Public

 the Java Learning Path (2)The first thing to understand is that the Java system is designed in three ways: J2se,j2ee,j2me (Kjava). J2se,java 2 Platform Standard Edition, we often talk about the JDK, the main point of this, it is the basis of the

In a POI operation, the following is a closed method that has recently encountered a failure to close the workbook, resulting in the inability to delete the corresponding file.Jar Package: Poi-3.8.jarFile f =NewFile ("/path/to/excel/file"); Workbook

Java generic methods@author Ixenos Generic methods can be defined in a normal class or in a generic class The type variable is placed after the modifier (such as public static), preceded by the return type When defined in

Sometimes, when we look at the Java error log, we see only one java.lang.NullPointerException, but do not see the wrong stack, because there is a parameter at boot time to choose the configuration: OmitstacktraceinfastthrowThe JVM does not see

Steps to use the array:(1) declaring an arrayDeclaring a one-dimensional array in JavaThe syntax is as follows:Array type [] array name;OrArray type array name [];(2) Allocating spaceThe syntax is as follows:Array name =new data type [array

Common logical operators Operator Chinese name An expression Description Example && And, and Condition 1&& Condition 2 Two conditions are true at the same time, the result is true;

Reprinted from:Sleep (), yield (), wait () The difference is detailed: http://dylanxu.iteye.com/blog/1322066The Join method is detailed: http://www.open-open.com/lib/view/open1371741636171.htmlDescription of difference:Sleep (millsec) method: Causes

Netty: data processing process, netty Data Processing Process Netty, as an asynchronous and event-driven network communication framework, helps us quickly develop high-performance and high-reliability network services. To better use Netty to solve

Quartz2.2.1 Quick Start, quartz2.2.1 I. First recognized quartz JobDetail job = newJob (HelloJob. class). withIdentity ("job1", "group1"). build (); Trigger trigger = newTrigger (). withIdentity ("trigger1", "group1"). startNow (). build

One GC problem locating and GC problem locating A colleague has a code segment that takes too long to execute and needs to be optimized, Hashmultimap map = ...; for (400 w * 96) {// computing process Bean = doCompute (); // cache the computing

Request Parameters are converted to the data type at the presentation layer to express the Data Type I. Introduction Note:There is no type concept for data transmission over HTTP. on the server side, the request parameter is String or String [] type

Java I/O technology and javao Technology 1. stream classification Most Java stream classes are derived from InputStream, OutputStream, Reader, and Writer. (1) Data Flow Input stream (subclass of InputStream class and Reader class) Output stream