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Preface Sometimes there are these requirements: 1. count the number of rows of a file 2. Calculate the number of valid lines of a source code. Exclude empty and comment rows 3. Unify the quantity and number of files in a directory Many languages can achieve these needs, but using Perl should be a good choice. Number of lines reading files It's easy to use Perl to read the total number of lines in a file (both empty lines and comments) open(FILE , O

4.9 create a read-only set Using Generics Problem You want the information in a set in the class to be accessed by the outside world, but you do not want the user to change the set. Solution Using ReadOnlyCollection Public class Lottery { // Create a list. List Public Lottery () { // Initialize the internal list _ Numbers = new List // Add Value _ Numbers. Add (17 ); _ Numbers. Add (21 ); _ Numbers. Add (32 ); _ Numbers. Add (44 ); _ Numbers. Add (

The system is dead, and the data is live. In some areas involving sensitive data, you may need to provide the client data access function. For example, a company has a WebGIS System Based on ArcGIS Silverlight API, which provides some common business functions to access some basic geographic data and basic business data. Some business data, due to confidentiality requirements, may not be directly provided by the system and needs to be accessed directly from the client. Accessing shapefile on t

:? 1 $ cp idegen.jar ../cyanogenmod/out/host/linux-x86/framework/idegen.jar Then execute it under the CyanogenMod directory:? 1 2 3) 4 5 /* $ . development/tools/idegen/idegen.sh Read excludes: 21ms Traversed tree: 54700ms*/ It took more than 54s to build on my computer, to view the directory, more than 2 files: Android.ipr and ANDROID.IML.3. Import to Android StudioOpen Android Studio,

Download all the files in the Headfirstpython Web site and extract the "Sketch.txt" in Chapter 3 as an example: Create a new idle session, import the OS module first, and swap the working directory for the folder that contains the file "Sketch.txt", such as C:\\python33\\headfirstpython\\chapter3 Copy Code code as follows: >>> Import OS >>> OS.GETCWD () #查看当前工作目录 ' C:\\python33 ' >>> os.chdir (' C:/python33/headfirstpython/chapter3 ') #切换包含数据文件的文件夹 >>> OS.GETCWD () #查

Database processing high concurrency two ways of vertical and horizontal differentiationvertically differentiate [distributed database]: separate database by module.Disadvantage: The design of each module of the system needs to be higher, cohesion and low coupling, the transformation is more difficult.At the same time, if the data reached a new critical point, there is still the possibility of poor access performance, such as an order database, the order quantity reached 10 million orders.horizo

SL series is the lowest end of the series, mainly for small business users, the configuration is relatively backward, is now facing the full production of discontinued; The Edge series is a new listing in 2010, is ThinkPad's first sub-brand, covering from 11 "small to 15" large series, a strong lineup, A young busines

Lost update: Two transactions update a row of data at the same time, the last transaction update will overwrite the first transaction update, resulting in the first transaction update data loss, which is caused by no lock; 1. Dirty reads: Dirty reading means that when a transaction is accessing the data and the data has been modified, and the modification has not been submitted to the database, another transaction accesses the data and then uses the data.e.g.The original salary for 1.Mary was 1

generated files after installing the operating system, capable of scanning the hard drive of the current operating system, loading the corresponding modulesA memory-based disk device for system initialization that uses a space in memory as memoryCentOS 5:/boot/initrd-version-release.imgTool Program: MKINITRDCentOS 6,7:/boot/initramfs-version-release.imgTool Program: DRACUT,MKINITRDAttention:A) is not required, when the kernel is self-compiled know the hard drive interface when the hard drive is

One of the functions of scriptmanager is to process partial updates on the page. For this, I think everyone knows. But what is his working principle? I will not answer this question from the front. Let's take a look at this. Currently, Ajax

Before reading this article, download the source code (portal) Mbprogresshud is an iOS class. When a background process is executed, a translucent HUD containing an indicator or tag is displayed. HUD is a replacement of uiprogresshud which is not

First, Address Book introduction The Address Book is an application of the Android phone, it is a contentprovider application, other applications can access the Address book, the contact person's crud operations. Second, the Address book database

§11.5 function expands into power series First, Taylor series If there is a derivative of any order in place, we put the series (1) Called the Taylor series at the point where the function is. The part of its preceding paragraph and its use is recorded, and Over here: The Taylor median theorem, which is described in t

MySQL InnoDB Transaction isolation level dirty read, Repeatable read, phantom read MySQL InnoDB transactions are isolated at four levels. The default value is repeatable read ). · READUNCOMMITTED ). Another transaction modifies the data but has not yet committed it, And the SELECT statement in this transaction reads th

　　Main content:1. Initial file operation2. Read-only (R,RB)3. Write only (W,WB)4. Append (A, AB)5. Read and write (r+)6. Write-read (w+)7. Additional write read (A +)8. Other methods of operation9. File modification and another way to open a file handleA. Operation of the initial fileusing Python to

Database transaction isolation level-dirty read, phantom read, non-repeated read, transaction level I. database transaction isolation level There are four database transaction isolation levels, from low to high: Read uncommitted, Read committed, Repeatable

Database transaction isolation level and dirty read, phantom read, non-repeated read, transaction level I. database transaction isolation level There are four database transaction isolation levels, from low to high: Read uncommitted, Read committed, Repeatable

I. Database transaction ISOLATION LEVEL There are 4 isolation levels for database transactions, from low to high to read uncommitted, Read committed, Repeatable read, and Serializable, which can solve the problems of dirty reading, non-repeatable reading, and Phantom reading one by one. √: May appear x: does not appear Dirty

1. Some problematic reads in the transaction: dirty read, non-repeatable read, Phantom readThe dirty read (Dirty Read) transaction T1 updated the contents of a row of records, but did not commit the changes. The transaction T2 reads the updated row, and then T1 performs the rollback operation, canceling the modificatio

I. DATABASE TRANSACTION ISOLATION LEVELThere are 4 isolation levels for database transactions, from low to high, READ UNCOMMITTED,Read Committed,Repeatable read, andSerializable, which can be resolved individually by each of the four levels Problems such as dirty reading, non-repetition reading, and Phantom reading. √: May appear x: does not appear