java programmer certification

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

(A.class); Propertydescriptor[] Pds=bi.getpropertydescriptors (); Because you get a group, you have to traverse it to determine which one is the desired method for (PropertyDescriptor Pd:pds) {if (Pd.getname (). Equals ("name")) {method readmethod= Pd.getreadmethod (); Method Writemethod=pd.getwritemethod (); Writemethod.invoke (a1,9); System.out.println (Readmethod.invoke (A1)); }}}}//a class, conforming to JavaBean's rule class a{private int x;public void setName (int x) {this.x=x;} public in

practices""Large Web site system and Java middleware implementation""Large Web site Technology architecture: Core Principles and Case studies"The way of code cleanliness"Enterprise Application Architecture Model"Principles, patterns and practices of agile software developmentThe essence of UML"Code Encyclopedia""Test driven development by Example""Programming Zhu Ji Nanxiong""Analytic Extreme Programming embraces change""Unified software Development

into all attributes and the specified properties:A, let's look at the notation for all the attributes:// get the entire class1. Class C = class.forname ("Java.lang.Integer");2. // get all the properties ?3. field[] fs = C.getdeclaredfields ();4.5. // define variable-length strings for storing properties6. stringbuffer sb = new stringbuffer ();7. // stitch each property into this string by appending the method8. // outermost public definition9. sb.append (modifier.tostring (C.getmodifiers ()) +

object method and class method, easy to useObject Method init start Class method method name begins with the class name (lowercase first letter) Use self as much as possible in the construction method to improve extensibility 2) If Class A is imported in class b , and class B is also imported in Class AThis can cause circular referencesWorkaround: Import the class (. h file, which is the declaration file ) with @class without #import reference But @class just tell the compile

Hello everybody, I am a Java programmer who has been working in Beijing for nearly 4 years, the character is introverted, like to study technology, will not much, but work enough, usually also learn some of their own interesting things, today is my first time in the life of the technology blog, simple to talk about their experience with you, After learning what will come out to share with you, in fact, ther

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