java learning path

uses this constant to specify that the package as the root package for the search action is the default value of Action,actions,struts,strtus2Specifies that the action from the root package of the action is forbidden. The default value is FalseAssuming that the constant is specified, convention only searches for the action class from the package that starts with that constant value.Specifies the package excluded from the search action. The default value is Org.apache.struts.*,org.apache.struts2

,int end,string str) is replaced with Str from start to end Public StringBuffer reverse () Flip of string Interception of StringBuffer Public String substring (int start) intercepts from the specified position to the end Public String substring (int start,int end) intercepts from the specified position to the end position, including the start position, not including the end position Note: The previous return value is StringBuffer, this time returning a string Conve

Char[] CHS =S.tochararray ();5 //flips the array6 reverse (CHS);7 //convert an array to a string8 return NewString (CHS);9}Flipping part of a string1 Public StaticString ReverseString (String s,intStartintend)2 {3 //string conversions that need to be flipped array ToCharArray () method4 Char[] CHS =S.tochararray ();5 //flips the array6 reverse (chs,start,end);7 //convert an array to a string8 return NewString (CHS);9

Packagecom.javaday_01; Public classText {intID; String name; Public intgetId () {returnID; } Public voidSetId (intID) { This. ID =ID; } PublicString GetName () {returnname; } Public voidsetName (String name) { This. Name =name; } Public Static voidMain (string[] args) {//instantiating an objectText Text =NewText (); //Assigning a value to an object Set methodText.setid (1); Text.setname ("Zhang San"); //to view the value of an object property Get methodSystem.out.println

corresponding characters in the both strings are equal ignoring Case. Characters C1 and C2 are considered the same ignoring Case ifAt least one of the following istrue: The characters is the same (as compared by the==operator) Applying the method Character.touppercase (Char) to each character produces the same resultapplying the method Character.tolowercase (Char) to each character produces the same resultparameters:anotherstring-The String to compare ThisString againstreturns:true ifThe argume

); //Total Doublesum=0; for(inti =0; I 5; i++) {System. out. println ("Please enter section"+ (i+1)+"class Entrance results:"); //The average score of single-door results DoubleScore=input.nextdouble (); Sum=sum+score; } //Average score Doubleavg=sum/5; System. out. println ("the average of 5 courses is divided into:"+avg); }

point:Are all structures used to handle multi-branch conditions.Different points:Switch selection structureCan only deal with the situation of the equivalence condition judgmentMultiple if selection structureThere is no restriction on switch selection structure, especially when a variable is in a continuous interval4. Summarize the selection structure:If selection structureBasic if selection structure: situations where single or combined conditions are handledIF-ELSE selection structure: Handli

, String sjh,string zj) {flag=false; intIndex=sjh.lastindexof ("-"); if(! (sfz.length () = = -|| Sfz.length () = = -) ) {System. out. println ("the ID number must be 16-bit or 18-bit!"); } Else if(Sjh.length () One) {System. out. println ("mobile phone number must be 11 bit!"); }Else if(index!=-1index!=0index!=4zj.length ()! = -) {System. out. println ("The landline number must be 4-bit and the phone number must be 7!"); }Else{System. out. println ("Registration Successful"); Flag=true; }} C

Array sorting in addition to the same handwritten bubble sort and selection sort as in C + +, the sort function is also supported, and the sort function is util. Arrays bag insideThe code below1 Package javalearning;2 import Java.lang.System;3 import Java.util.Scanner;4 import java.util.Date;5 import java.util.Arrays;6 7 Public classHelloWorld {8 Public Static voidMain (string[] args) {9Scanner input=NewScanner (System.inch);Ten intarray[]=New int[Ten]; One for(intI=0;iTen

1: What is an exception?An event that interrupts the normal instruction flow.An exception is an object in which the virtual machine generates an exception object when an exception occurs.The class that generated the object is provided by the JDK　　　　Explain:Throwable is the base class for all exception classesError refers to errors generated by the virtual machine at run time, and when an error occurs, the virtual opportunity shuts downException refers to an exceptionRuntimeException Run-time exc

1: Package and access rightsTo place a class in a package, you need to use the package nameThe use of the-d parameter at compile time the function of this parameter is to generate the corresponding folder according to the package nameThe whole of a class should be "package name" + "." + "class name"Naming conventions for package names:Require that all letters of the package name be lowercasePackage name in general, is your domain name upside down writeA class in a package accesses the conditions

subclass does not assign a value to the parent class's variable, the parent class variable is not assigned, so the subclass must assign a value to the parent class variable① can assign a value directly to a parent class variable in a subclass② can call the Super method to invoke the parent class constructorModified Student Class: class Student extends persion{ int grade; Student () {System.out.println ( "Student parameterless constructor" int age,int grade) { super (Name,age);

,int b) {Boolean BL = a = = B;return BL;}C: Get the larger value in two numberspublic static int Getmaxnum (int a,int b) {int maxnum = (a>b)? A:B;return maxnum;}D: Print star rectangle for m row n columnsScanner sc = new Scanner ();int m = Sc.nextint ();int n = sc.nextint ();PRINTMN (M,n);public static void printmn (int m,int n) {for (int i=1;ifor (int j=1;jSystem.out.print ("*");}System.out.println ();}}E: print nn multiplication tableScanner sc = new Scanner ();int m = Sc.nextint ();int n = sc

; string attribute = (string) request.getattribute ("name"); System.out.println ("Myservletrequestlistener requestdestroyed and Request attribute:" + attribute); } public void requestinitialized (Servletrequestevent servletrequestevent) {servletrequest ServletRequest = Serv Letrequestevent.getservletrequest (); HttpServletRequest request = (httpservletrequest) servletrequest; Request.setattribute ("name", "requestinitialized"); System.out.println ("Myservletrequest

JDBC (JavaDataBaseConnectivity): it facilitates applications to operate on database data through jdbc. basic steps: (pilot the driver into the database) {1. connect to the database first to obtain the object of the database (1. first load the database driver 2. obtain the connection through the basic information of the database. obtain operations through connection JDBC (Java Data Base Connectivity): basic steps for applications to operate databases t

BackgroundBecause the project needs to be used in the Java Web project to map, manufacturers provide a DWG format of the map, and we are using Mapxtreme Java technology, so we should first convert the DWG format map to Mapxtreme Java can parse the format, that is, the GST format. On this aspect of information, very few online, coupled with software difficult to f

( springbootservletinitializer.java:85) + At Org.springframework.web.SpringServletContainerInitializer.onStartup ( springservletcontainerinitializer.java:169) - At org.apache.catalina.core.StandardContext.startInternal (standardcontext.java:5292) the At Org.apache.catalina.util.LifecycleBase.start (lifecyclebase.java:147) * ... Ten more $ caused by:java.lang.IllegalStateException:Detected both Log4j-over-slf4j.jar and bound Slf4j-log4j12.jar on the CLA SS

System.out.println ("Enter Circle radius First:"); R=sc.nextint (); //1. Wait for the user to enter a radius, 2. Store the radius of the input into the variable r area=pi*r*r; Round=2*pi*r; System.out.println ("Round area area=" +area); System.out.println ("Round circumference round=" +round);}} As to the learning of this procedure, the summary is as follows:I. Summary of the Scanner classScanner, like Heloworld, are classes that derive from the unde

Although officially graduated only 5 days, can work for a full six months. Suddenly from campus life to crowded bus work every day those feelings, deeply aware of the university years I wasted a lot of time and learning opportunities! Remember the end of the college entrance period, experienced a lifetime of painful experience (by the family sent in high hopes but the test of the mess), grew up! This university graduation, without those pain, also

javax.servlet.http.HttpSessionAttributeListenerandHttpSessionBindingEvent Request A servlet request has started being processed by Web Components javax.servlet.ServletRequestListenerandServletRequestEvent Request Attribute added, removed, or replaced javax.servlet.ServletRequestAttributeListenerandServletRequestAttributeEvent Use the @WebListener annotation to define a listener to get events for various operations on the particular W