java programmer ii

some time ago, in a lot of blogs and micro-blog burst out of the 12306 some loopholes in the website of the Ministry of Railways, as such a large project, it is not impossible to say that there are loopholes, but the loopholes are some novice programmers will make mistakes. In fact , the SQL Injection vulnerability is one. As a rookie little programmer, I know nothing about SQL injection, so I took the time to learn a bit. Now to share the results of

-0=256Byte ..... (byte) 300; 44 300-44=256Equivalent to the data with strong turn-256;Range of Byte: 128 ~ 127128:10 million-128:10000000 (1 Here is the sign bit, also the value bit)3: Default conversion of data type conversionsByte,short,char--INT--long--float--doubleLong:8 bytesFloat:4 bytesA: Their underlying storage structure is different.The range of data represented by B:float is larger than the range of longLong:2^63-1float:3.4*10^38 > 2*10^38 > 2*8^38 = 2*2^3^38 = 2*2^114 > 2^63-14:

) object C) interface type conversion: Automatic conversion, expression: 1, the type of the automatic lifting expression if there is a long, the result is a long expression if there is a double, the result is double. 2, cast operator 1, arithmetic operator 2, relational operator 3, logical operator 4, bitwise operator 5, assignment operator 6, trinocular operator (boolean expression)? A:B control Statements: 1. Sequential structure 2. Select Structure a) if b)If else c) switch multi-value select

execution. For example, the data inserted into the database can not be deleted!9. Distribution filteringWhen we enter the (F5) method, we can also access its external libraries (such as java.*), we may not need this library, we can add a filter on the Perference tab page to exclude this package.10. Entering, jumping and returningI put this on the last point, during the commissioning process, these are things that must be understood (preferably master

(supplementary character This is a very necessary explanation. Utf-16 is Unicode) is a way to implement. Namely put unicode16 code element A sequence of 1 2 16 In the basic multi-lingual level, each character is represented by a number of lines, often referred to as a code unit,while auxiliary characters are encoded with a pair of contiguous code units. The encoded values in this form fall within the free 2048 bytes of the basic multilingual level , often referred to as the alternate area (

The article is reproduced in its own CSDN blog.Currently working in the outsourcing company, the company intranet can login csdn, no way to log into the blog park, there is no way to continue to start writing on the csdn.Since the newly-arrived computer is not yet configured, you can only use someone else's computer to test your previous needs temporarily. It's not too late to work, I feel I should tidy up the next work, study plan.Just looked over a few blog, to see the experienced old-timers r

returningI put this on the last point, during the commissioning process, these are things that must be understood (preferably mastered):f5--Enter: Moves to the next step, if the current row has a method call, the control jumps to the first line of the called method execution.f6--jumps: Moves to the next line. If there is a method call on the current line, it is moved directly to the next line. Does not enter inside the called method body.f7--returns: Jumps out of the current method and continue

 Dark Horse Programmer--java Basic Learning Note 8I. Summary of the contents of the notes:Object-oriented (array tool object creation-document annotations-Singleton Design patterns memory plots), inheritance, single inheritance, and multiple inheritance.Second, the introduction of common content:1. Benefits of Inheritance: Improved reusability of code, relationship between classes and classes, developmen

When a Java programmer has been a programmer for one or two years, he may feel that he does not know what to learn, because the project he or she is familiar with is already competent. However, if you have higher requirements, you still need to find them. Fortunately, there are many network resources. Here is a summary: I. Web Programming1. Client Web Programming

interfaceThreaduserunnable () {}//constructor Function Public voidrun () {System.out.println ("I am a thread instance of the threads class and have implemented the Runnable interface class as Parameters!"); System.out.println ("I'll hang up for 1 seconds!"); System.out.println ("Back to the main thread, please wait for jn0-120 e20-040, just hang up the main thread may not wake up!" "); Try{Thread.Sleep (1000);//Suspend 5 Seconds} Catch(interruptedexception e) {return; } //if the run () method i

non-static variable, subclass non-static code block, subclass constructor method. Three. I++,++i the difference between this is Baidu bar next talk about the code flowPublicClassPROGRAM2 {static {int x = 5;//declares a local variable, has no effect on the back} static int X,y;//default 0 public Static void main (String[] args) {x-- ; //x=-1 MyMethod (); SYSTEM.OUT.PRINTLN (x + y++ + x); //1+0+1} private static void mymethod () {y=x++ + ++x;//equivalent to y= (x + +) + (++x) from right to left

DoSomething ("a three");DoSomething ds2 = new DoSomething ("John Doe");thread T1 = new Thread (DS1);Thread t2 = new Thread (DS2);T1.start ();T2.start ();}}Execution Result:John Doe: 0A three: 0John Doe: 1A three: 1John Doe: 2John Doe: 3A three: 2John Doe: 4A three: 3A three: 4Process finished with exit code 02. Multithreading example of extending the thread class implementation/*** Test extended thread class implementation of multi-threaded threads* @author leizhimin 2008-9-13 18:22:13*/Publicc

of the text box to the specified location * / Private void savecontent() {BufferedWriter writer =NULL;Try{writer =NewBufferedWriter (NewFileWriter (Msavefile)); String content = Moutputbox.gettext (); Writer.write (content); }Catch(IOException e) { }finally{Try{if(Writer! =NULL) {writer.close (); } }Catch(IOException e) {}; } }/** * Loading file contents * / Private void LoadFile(File file) {if(File.exists ()) {Minputbox.settext (Fi

two kinds of polymorphism: universal polymorphism and specific polymorphism. The difference is that the former does not restrict the type of work, allows the same code to be executed on different types of values, the latter is valid only for a limited number of types, and may have different code to perform for different types of values.The generalized polymorphism is divided into the parameter polymorphism (parametric) and the inclusion polymorphism (inclusion), the specific polymorphism is div

final modifier local variable : The value of the base type cannot be changed. Reference type: The address value of the reference type cannot be changed, but the value of the heap memory of the object can be changed. */class Student {int = 10;} Class Finaltest {public static void main (string[] args) {//local variable is the base data type int x = 10;x = 100; SYSTEM.OUT.PRINTLN (x); final int y = 10;//cannot assign a value to the final variable y//y = 100; System.out.println (y); System.ou

pt = (parameterizedtype) t;//strong go to its child class $ /**Panax Notoginseng * type[] getactualtypearguments () - returns an array of type objects that represent the actual type parameters of this type. the Type Getownertype () + returns a type object that indicates that the type is one of its members. A Type Getrawtype () the returns a Type object that represents a class or interface that declares this type. + */ - $t = Pt.getrawtype ();//class or interface of

Long time no write, tell me about my own network to the Java programmer this way. Hope to give some friends a little inspiration.Since 12, I started learning Java with the help of leaders and colleagues. I bought a "crazy Java handout" from Li Gang, and the logic of learning Java