Java

Generally when we operate the database, we need to open and close the connection frequently, and create a database connection is often expensive, so we need to avoid this situation, where we can create a connection pool, when the operation of data,

All the data in the computer is stored in binary form. Bit arithmetic is the direct manipulation of binary data in memory, so processing data is very fast. In the actual programming, if can skillfully use bit operation, can achieve 42 to dial the

public class TestClass {public static void main (string[] args) {Student stu1 = new Student (); Comp C1 = new Comp (); c1.band= "Lianghe County"; stu1.comp = c1;c1.band= "1111"; System.out.println (Stu1.comp.band);}} Class Comp {String band;} Class

Use of 1.nullIn Java, NULL is a keyword used to identify an indeterminate object. Therefore, you can assign null to a reference-type variable, but you cannot assign null to a primitive type variable. For example, we define a variable when we do this:

string is a literal in Java . The string class is immutable, and any change to the string class returns a new String class object. The following describes string and constant pools in Java. 1. The string is not the first of 8 basic data types,

The Count-and-say sequence is the sequence of integers beginning as follows:1, 11, 21, 1211, 111221, ...1is read off as "one 1" or 11 .11is read off as "two 1s" or 21 .21is read off "one 2 as, then one 1" or 1211 .Given an integer n, generate the

Package Org.apple.date;import java.text.simpledateformat;import Java.util.calendar;import java.util.Date;/** * Cycle time * @author Shaoyu * */public class Cycledate {public static void main (string[] args) {SimpleDateFormat dateformat=new simpled

Package com;import com.sun.org.apache.bcel.internal.generic.if_acmpeq;public class test  {public static void main (String[] args)  {string s1= "2018-01-25"; String s2= "2018-02-25"; Java.text.dateformat df=new java.text.simpledateformat ("Yyyy-MM-dd"

The current Java Enterprise Development Framework, which we commonly use roughly includes the IOC AOP MVC ORM Framework1, IOC Spring is a very good ICO container, the idea is very simple, with a collection object such as map to cache objects (the

Many times it is easy to confuse the static with the final keyword, where static acts on the member variable to indicate that only one copy is saved, and final is used to ensure that the variable is immutable. Look at the following example: Public

Variable parameters are supported in JavaIt means: The number of parameters can be written as required, you can write 1, 2, 3 、、、、 They are saved in an array of parameters.However, these parameters have some constraints: they must be of the same

1. Abnormal effect: improve the interactivity of the software .For example, login examples:(the correct return is 0, if the user can not find is-1, if the password is not correct, that is-2): These are required to write the login method and the

1.JDK and Eclipse directory structure operations1) Open the JDK directory structurePwdCd/optCD JDKLs2) Open the directory structure of EclipseCd..CD EclipseLsInstallation and configuration of 2.JDKInstallationOracle provides two products for the

There are three classes in Java and the package that synchronize the behavior of a batch of threads, namely Countdownlatch, Semaphore, and Cyclicbarrier.CountdownlatchCountdownlatch is a counter lockout, the main function is to block the current

Objective: In the new concurrent package, Blockingqueue solves the problem of how to efficiently and securely "transfer" data in multiple threads. These efficient and thread-safe queue classes provide great convenience for us to quickly build

　　　　　　　　　　　　　　　　　　　　　　Java Time Class (data Class)1. Thedata class (without considering internationalization, many methods are obsolete in Java.util.Data package) the parent class (is the class is not the interface contains the direct subclass 3):

JMS -- Java Message ServiceJAVA the messaging service , messages enable both ends of communication .used to access standards for message-oriented middleware API , he provides vendor-agnostic access methods to access messaging services. features :

Kettle series-1. kettle source code acquisition and operation, kettle-1.kettle I was a little excited when I wrote my blog for the first time. There must be a lot of improvements. Hope haihan. Kettle is an open-source software that I have studied in

WeakHashMap, androidweakhashmap WeakHashMap: when there is no reference to the key except for its own reference, the map will automatically discard this value.Code In this example, two Map objects are declared. One is HashMap and the other is

Java Web development and learning (2)-configure the Tomcat server and javawebtomcat1. Download the Tomcat server Tomcat is a free and open-source JavaWeb server. Tomcat official website is http://tomcat.apache.org/ I use atat7.0 and download the