java code review checklist

This section review Java Common I/O, input and output streams.First put the sample code, convenient reference, can be easily read. PackageRe08;ImportJava.io.*;ImportJava.util.Scanner; Public classIotest { Public Static voidMain (string[] args) {File file=NewFile ("D:/1.txt");//File Creation if(File.exists ()) {file.delete (); } Else { Try{file.c

equals (object) method, then each object in both objects is called hashCodemethod must produce the same integer result, if two objects are not equal according to the equals (object) method, they hashCode do not require unequal calling methods, but for hash tables, the performance is best unequal. Therefore, we'd better rewrite.As mentioned earlier, the String class overrides the Equals () method, but the string class also overrides the Hashcode () method, which is the hashcode () generated from

later4. Constants, variables:There is a lot of data in the program to represent the state of the program, some data will change in the process of operation, there areSome data will not change during the program's operation. These data are called variables and constants, respectively. Variable in theMust be declared before use: Data type variable name variables can be divided into: local variables, member variables, method parameters,Exception handling parameters.Local variables: Variables defin

1. What is the Java method?In our daily life, the method can be understood as the solution to do something and take it.In Java, a method is a way to accomplish something or to implement a function.Method implementation, there are a number of statements that are used to accomplish some meaningful function-usually working with text, controlling input, or calculating values.We can implement (or call) the metho

class name can be called.After the method is static, it is easy to use, but the class can also be used by other programs to establish objects, in order to be more rigorous, forcing the class cannot establish objects, you can do this by privatizing the constructor .Person p = new person ("Zhangsan", 20);What has been done in this sentence?1. Because new uses Person.class, the Person.class file is first found and loaded into memory.2. Execute the static block of

our own defined Servlet class . 5. Servelt the relationship between core APIs UML diagram:6. The start of the servlet (default is a singleton servlet) (the Init method is executed the first time the servlet is called by default)• The servlet container loads the servlet at the following times:–servlet loading some servlets automatically when the container starts– After the servlet container is started, the customer makes the first request to the servletAfter the –servlet class file is updated,

an exception.------------------------------------------------------Inner classStatic Inner classes: Create classes in classes, static adornments, and only static properties and methods of the perimeter class can be called.member Inner class: A class created in a class that cannot use the static modifier.Anonymous inner class: Creates an object directly in the method.Local inner class: A class that is created in the method body, has no modifiers, and can access only the final decorated constants

("helloc3p0"); * 3. Gets the database connection from the DataSource instance. */@Test Public voidTestc3powithconfigfile ()throwsexception{DataSource DataSource=NewCombopooleddatasource ("Helloc3p0"); System.out.println (Datasource.getconnection ()); Combopooleddatasource Combopooleddatasource=(Combopooleddatasource) DataSource; System.out.println (Combopooleddatasource.getmaxstatements ()); } @Test Public voidTESTC3P0 ()throwsexception{Combopooleddatasource CPDs=NewCom

, or has a default initialization value.Format: variable name of data type = initialization value;Categories of variables in 4.JAVA:A. Data type:Basic data type: Numeric type (integer type: byte/short/int/long; floating-point type: float/double)Character type (char)Boolean Type (Boolean)Reference data types: Classes (Class)/interfaces (interface)/arrays ([])Integer defaults to: int decimal default: DoubleB. Type auto-boost: High end Double/flaot/long Intàbyte/short/char5. Arithmetic operator: +-

1. Key wordsConcept: Words that are given special meaning by Java.Example: Declaring a class keyword: classAccess Rights keyword: publicstatic modifier keyword: staticNo return value type keyword: void2. IdentifiersConcept: A name used to standardize a custom in a programComposition: Alphanumeric underscore $Spec: Cannot start with a numberCannot contain spacesCharacters other than $ cannot appearCannot use keywordsNote: Identifiers in Java are strict

Java Web review Part 6: Servlet thread security, javawebservlet I have mentioned a lot of basic Servlet knowledge before. This article focuses on Servlet thread security issues.1: multi-threaded Servlet Model To understand Servlet thread security, we must first understand how the Servlet instance is created and what its mode is. By default, the Servlet container creates only one Servlet instance for the dec

up execution eligibility.After notify, back to the temporary state, not necessarily run, because not necessarily rob the executive right.Because our thread inherits the thread parent class, we use super to call the parent class constructor method to give the nameSell Tickets:Multithreading shares the same resources, defined as static. Ticket--, 1:2, number 3rd is first printed out as a dual-core CPU, because the callPrinting at the command line is also a program. If not defined as static, ticke

"); the same as the code in the same sentencePrintWriter writer = Response.getwriter ();Writer.write ("China");C. Using response for file download:String Path = This.getServletContext.getRealPath ("/China. jpg");String fileName = path.substring (path.lastindexof ("\ \"));Response.setheader ("Content-disposition", "Attachment;filename" +urlencode r.encode (filename, "UTF-8"));//Set the response header, Tell the browser that the response is a download r

Java class loading takes a full-fledged delegation mechanism, and the subclass will delegate to the parent class when the class is loaded by default, but the subclass will attempt to load the class itself when the parent class is not loaded. This mechanism can effectively prevent a class from being loaded multiple times, and also to some extent prevent rewriting the JDK's own class "Java itself to restrict

Java web crawler Technology, the discovery of web crawler technology first divided into the following steps:1. Open Web Link2, the page code with a BufferedReader storageHere is a code example that I made:In the process of learning web crawler first to import two packages: Htmllexer.jar,htmlparser.jarpublic static void Main (string[] args) { try { URL url = new

Tomcat's lib. public class Hello extends HttpServlet {private static final long serialversionuid = 1L; JDBC driver name and database URL static final String jdbc_driver = "Com.mysql.jdbc.Driver"; Static final String Db_url = "Jdbc:mysql://localhost:3306/test"; The user name and password of the database need to be static final String user = "root" according to your own settings; Static final String PASS = ""; /** * @see httpservlet#httpservlet () */public Hello ()

to access the remote database, you need to modify the section:--For Master (this refers to the host that created the database)A. Modifying the/etc/postgresql/9.4/main/postgresql.confOriginal content:# listen_addresses = ' localhost ' after modification ( Remove the # comment):listen_addresses = ' * ' #监听来自所有ip的访问数据库请求B. Modifying/etc/postgresql/9.4/main/pg_hba.conf (hba=host-based authentication)# IPv4 Local connections:host all 127.0.0.1/32#新增内容, you can add several IP segments tha