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Common encryption methods in the project base64, AES, MD5, sha-1, base64sha-1Today, I reorganized several encryption methods that were frequently used in previous projects, we found that we didn't really understand these encryption methods in the past. First of all, from the nature of encryption, it is to output some data with an indefinite length according to certain encoding rules as a data string of a certain length. This is what I understand. Diff

The opening crap .If we want to do the memory optimization work, still need to understand, but this piece of knowledge is purely theoretical, it may seem a bit dull, I try to put this piece of content in accordance with certain logic to go through. First of all, why we should learn the mechanism of garbage collection, I probably summed up a few points:1.方便我们理解什么样的对象，什么时候，会被系统回收掉2.有助于我们后面的内存优化3.了解这一块的知识也能提升自己的知识广度，和同事一起装逼的时候有话题4.如果有面试的需求的话，了解这一块，也能从容面对

For example, how many digits do I have (the digits behind the decimal point are not fixed): 1, 155.0552, 122.1963, 0.9631? How can I make the last decimal point of these digits + 1, or-1? For example, in the case of + 1, we hope to get: 1, 155.0562, 122.1973, and 0.9632. For

At first glance, this question is really good for anyone. when the group sees this question, they are scrambling to give their views. The simplest way is to traverse each number, then toString () to see how many 1 s are in it, and finally add up all. this is the way we get the standard answer. Three people in the group wrote three stupid methods and ran out. The three stupid methods were both interesting and different. The implementation of the progra

The Linux kernel source code contains the file Linux/compile. H. Therefore, first analyze the content in the file as the beginning. 1. Content not defined during compilation The first content of this file is the judgment of macro _ Assembly _. The function of this macro is to avoid defining subsequent content during compilation. This macro is added by using the-D option in the compiler. The aflags parameter also contains the macro definition. During

Original post address: http://blog.csdn.net/wangyihust/archive/2009/02/05/3863758.aspx select 1 from table; and select anycol (any row in the destination table set) from table; and select * from table in terms of function is no difference, it is used to check whether there are records. It is generally used for conditional query. 1 in select 1 from is a constant (

Processes communicate through pipelines 1. Process pipelines 1. In Linux shell commands, you can use the pipeline operator '|' to connect processes. Here, we use pipe to achieve this effect in the program. Pipe FunctionThe prototype is as follows: # Include Int * pipe (int file_descriptor [2]); Function Description: File_descriptor is an array pointer consisting of two integer file descriptors. All data wr

I. You do not need to worry about the problem where 1 = 1 in Multi-condition queries. For example, if you query a page and have multiple options to query, you can also select and enter the query keyword on your own, the code is roughly as follows: Copy codeThe Code is as follows: string MySqlStr = "select * from table where "; If (Age. Text. Lenght> 0){MySqlStr = MySqlStr + "Age =" + "'Age. text'";} If (Ad

One, no where 1=1 in the multi-condition queryFor example, if you do a query page, and there are multiple options, but also let users choose and enter the query keyword, then, according to the usual dynamic structure of the query statement, the code is generally as follows: Copy Code code as follows: String mysqlstr= "select * from table where"; if (age.text.lenght>0) { mysqlstr=mys

Accp8.0 conversion Materials Chapter 1 MySQL advanced query (1) Understanding and exercises, accp8.0 advanced Query I. Word Section ① Constraint ② foreign key foreign ③ references reference ④ Subquery ⑤ inner internal 6 join connections Ii. Preview 1. Modify the keywords of the table SQL statement RENAME Modify Table Name CHANGE Modify Field 2. Which keyword can

Chapter 1 Common EL expressions and chapter 1 el expressions ElMost commonIn the following scenarios: Read attributes from the configuration file If the value is missing, configure the default value. El internal String use String method Three-object Operator Regular Expression System properties) Call Original system functions Direct file injection Read the return value of another bean Function

# Include # Include Using namespace STD; Struct point{Int X, Y;};Point bufa [8] ={{-2, 1}, {-1, 2}, {1, 2}, {2, 1 },{2,-1}, {1,-2}, {-1,-2}, {-2,-