what value of null

Some questions to note about PHP operating MySQL database 1. Exceptions to semicolons For MySQL, the first thing you have to keep in mind is that each line of the command is separated by a semicolon (;) As the end, but ... There is no absolutely

Yii uses URL component beautification management method, Yiiurl component beautification Examples of this article describe how Yii uses URL component beautification management. Share to everyone for your reference, as follows: Urlmanager components

References use the "." operator and pointers use the "*" and "->" operators, which are the basic and most familiar differences between the two.First, there is no so-called null reference. A reference must always represent an object. Therefore, C ++

This problem has actually plagued me for a long time. I have asked many people what is "null? What's the purpose? Most people answer: "null is a special 0 defined by the system. Pointing your initialized pointer to it can prevent the evil effects

First, Socket IntroductionSocket is a way of process communication, that is, some API functions that call this network library implement the data exchange between related processes distributed in different hosts.Several definitions:(1) IP address:

1. hashmap 1) Data Structure of hashmap Hashmap is a combination of arrays and linked lists (called "linked list hash" in the data structure), as shown in: When we put an element in a hashmap, we first calculate the hash value of the Key to the

Mongoose Reference Manualtags (space delimited): MongoDB In general, we do not directly use MongoDB functions to manipulate MongoDB database Mongose is a set of Operations MongoDB database interface.SchemaA database model skeleton, stored as a

Null indicates that an object is defined with a value of " null "; Undefined indicates that this value does not exist. //typeof undefined"Undefined"Undefined: is a primitive value that represents " none " or " missing value ", thatis, there

1, PostMessage only put the message in the queue, regardless of whether the other program is processed to return, and then continue to execute, this is an asynchronous message delivery function. The SendMessage must wait for the other program to

JS syntax1. JavaScript data typeJavaScript has a dynamic type. This means that the same variables can be used for different types: strings, Numbers, Booleans, objects, arrays, undefined, and nullObject:var person={firstname: "John", LastName : "Doe"

Collection interface:　　1. The root interface of a single-column collection class.2. Define the method that can be used to manipulate list and set--adding and deleting;3. Inherit from the Iterable interface, which provides a iterator() method:

"Detailed study of Java collections" List,set,map usage and differencesCollection is the most basic set interface, and a collection represents a set of object, the collection element. Some collection allow the same elements while others do not. Some

Object-oriented concepts:-----------------------Object-oriented programming Oop:object oriented programmingProcess-oriented Programming ooa:oriented object analyzeObject-oriented design ood:orientedObject:Class:Package: EncapsulationInheritance:

1. Array (static initialization-FAQ)public class test1{public static void Main (string[] args) {Int[] Arr=new int[3];Arr=null;System.out.print (arr[1]);}At this point the program will error: NullPointerException: null pointer exception, the ARR

Static proxy1. Role Analysis of static agents (UML drawing recommends using STARUML software)Abstract roles---generally implemented using interfaces or abstract classes.It's really the role---being represented.Proxy role---Proxy real role-the agent

Method One:request.getparameter ("name")Method Two: annotated @requestparam@RequestMapping ("Testrequestparam") // annotations in the way public String Filesupload (@RequestParam (value= "Inputstr", Required=false) String inputstr,

5. Data Structure 5.1 data structure Introduction(1) VectorAll elements of a vector must have the same type (pattern)(2) ListThe list can be non-homogeneousList can be indexed by location: lst[[2]]Extract sub-list: Lst[c (2,5)]The list can have a

In the development of Web projects, inevitably encountered a variety of Web page data processing, such as the user entered in the form of the phone number, mailbox, amount, ID number, password length and complexity of the verification, and back to

The composition of the class: Property (member variable, Field). Method (Member method, function, method). Properties : member variables VS local variablesSame point: 1. Follow the format of the variable declaration-data type

Transferred from: http://www.360doc.com/content/090313/10/26262_2794855.html 1.Criteria Hibernate has designed criteriaspecification as the parent interface for criteria, and the criteria and Detachedcriteria are provided