, execute. r--Read only, can be deleted to see the permissions of the directory;Directory permissions: R-List PermissionsW Create delete file or directoryx whether to enter the directory10. Cat display text file contents(1) Cat file(2)-N Display line number11, TAC reverse display text file content, contrary to cat command12, more paging view files(1) More files(2) blank page, carriage return line down; CTRL + C or Q cancel13, less paging display, you can page forward(1) Less files(2) PageUp up t
Java learning path-Spring's HttpInvoker LearningHessian and Burlap are both based on HTTP, and both of them solve the firewall penetration problem caused by RMI. However, when the passed RPC message contains a serialized object, RMI wins Hessian and Burlap. Hessian and Burlap both adopt private serialization mechanisms, while RMI uses
table.-css_xhtml: the templates in this topic are similar to the templates in XHTML themes, but they will be used for layout and typesetting using CSS-ajax: the template in this topic is based on the XHTML theme of the German template, but adds some Ajax features. 2. Modify the Theme:-through the UI Tag's theme Property-in a form, if the theme property of a UI tag is not given, it will use the theme of this form-add a Theme property in page, request, session, or application-modify the Struts.u
little bit more than C + +, for example: int i = f ();int F () {return 11;}? The function f () is required to be declared in C + +, but it is not required in Java.And the following code:1 Public classtest{2 3 inti = g (j);//Illegal forward reference4 5 intj =f ();6 7 intGinti) {8 9 return2 *i;?Ten One }? A - inti =f (); - the intF () {return11;} - -}?It's not working in
(^): Same as false. The difference is true;or (|): As long as one is true;With (): As long as there is a false is the false;Three mesh operator: judgment statement? "For true execution", "for false execution";Calculation operators
Operator
Description
+ 、—、 *,/,%, =, + + 、--
Basic operators
12>>3
Move right 3 times, equivalent to 12/2 of the 3-time Square
3
Move left 3 times, equivalent to 3*2 3-time
A+=b
Last semester of the object-oriented programming class is in C + + language, to Java, the idea should not be much change, but the grammatical part of some changes, here to record (idea blown)ImportJava.lang.System;Importjava.util.Collections;ImportJava.util.Comparator;ImportJava.util.Scanner;Importjava.util.Arrays;classa{ Public intNUM1; Private intnum2; PublicAintNUM1,intnum2) { This. num1=NUM1; This. num2=num2; } voidCreate () {}}classB
throughout the class. The member variables of a class are also classified as static variables (class variables) and instance variables.If you precede the type of a member variable with the keyword static, such a member variable is called a static variable. The valid range of static variables can span classes, even within the entire program. int x=10; static int y=10; Here x is an instance variable and y is a static variable.Local variables: Variables defined in the method body of a class, loc
Simple Java Class Development general principles:
The name of the class must be meaningful, and then how to say, let people see it.
All properties within a class must use private encapsulation and provide the Setter,getter method
There can be more than one construction method in a class, but you must keep a parameterless construction method
No output statements are allowed in the class, all outputs must be given to the
Class r
Java: the path from basic to advanced learning-creation of Sudoku games (1), java advancedPreface
Most people have played this game, so the specific game itself is not described.
See Baidu Encyclopedia: http://baike.baidu.com/subview/961/10842669.htmRules and objectives
The rule of DT independence is simple, that is, d
, which can be accessed within the same package
Protected
This class, subclass, and package can be accessed
Inheritance: extends (keywords)Cast: instanceceof (keyword)Final: The final modification cannot be changed, cannot be inherited, cannot be rewritten;Abstract class:Modified with abstract;cannot be instantiated directly;Abstract method is used to modify the method.Abstract classes are generally used as parent classes of other classes, but must be rewritten;Can
For Yesterday Java Learning Road (a)--thinking in Java static method of the class can not be accessed to create a non-static class, the internal class is modified to be static class, easy to operate. Now gives you a second, highly efficient way to add no deletions. You can copy and paste an inner class from a class you create into a class, and as an external clas
If this class can be cloned, the next step is the clone method: Public Objectclone () nbsp { try{ countersetobj= (CounterSet) super.clone (); obj.packets= (int[]) packets.clone (); Obj.size=size; Returnobj; }catch (clonenotsupportedexceptione) { Thrownewinternalerror ("Unexpected clonenotsupportedexception: "+e.getmessage ()); } }
class method The method to begin writing the class: /** *setthe Packetcounters * (suchaswhenrestoringfromadatabase) */ Protectedfin
the variable name arr in the stack area, new int[5] in the heap area, open up 5 contiguous space in the heap area, the default int is 0When we re-assign arr to a new variable, it just gives the new variable the memory address.
static initialization of arrays
Dynamic initialization: int[] arr = new Int[5]Static initialization:Format: data type [] Array name = new data type []{element ...}Simplification: data type [] Array name = {element ...}
traversal of an array
If it's
Recently in the "tingking in Java" This book study, the second chapter exercises the topic of practice encountered a problem, No enclosing instance of type test1 is accessible. Must qualify the allocation with an enclosing instance of type test1 (e.g. X.new A () where X was an instance of Test1.The reason for the error is that the main method is static and cannot access the dynamic class you define, that is, you cannot create a reference to the class.
months to study this 1000 more pages of the big, and then the third time around 15 days can be done, notes a large book! From then on.Choose the right book and bury the research. I'm sure we'll get started soon!Learn the Java language 8 simple parts, this is just the beginning of our study of the Java language! These all understand that at best a Java programmer
Alas, the front has been skipped, a look at the pure text description on the headache.This section is about Java data types, there are eight basic types, of which the int,short,long,byte four are shaped, is pure numbers, the size is 4,2,8,1 bytes, a byte is composed of 8 01, the highest bit is the sign bit, 0 is an integer, 1 is a negative number, For example, the range of byte is 128 to 127. I don't know the rest of it.Floating-point types have float
--system library, library informationSELECT * FROM Table_constraintsWHERE table_name = ' xxx '; (3) Remove the unique constraintALTER TABLE TB2Drop index name; (4) CHECK constraintsYou can limit the value of a field by setting its value, such as gender, age range, etc.MySQL supports checking the syntax of constraints, but without implementing constraints, MySQL does not check constraints CREATE TABLE Xuesheng (Gender ...Age ...Check (gender= ' male ' or gender= ' female '),Check (age>8 and age);
\jdk1.7.0_72\bin* B: Then enter Javac and Java separately, if some content is displayed correctly, the installation is successful.# # #01.11_java Language Basics (Directory interpretation under JDK installation path) (learn)* A:bin Directory: This directory is used to store some executable programs.* such as Javac.exe (Java compiler), Java.exe (
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