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Welcome to my blog: blog.scarlettbai.com View more articles Recently received a demand, to batch generate promotional code, first we know that the promotional code effects have the following two points:1: Non-repeatable2: Can not be pushed to measureAbout these two points, our ideas are broadly divided into the following categories:1: After each generation of a random

Digitalocean is my favorite VPS service provider and currently has 10 or so Digitalocean VPS servers on hand. After more than three years of Digitalocean, I found Digitalocean a little bit of a trick. For example, if your account is not logged in after a long period of operation, Digitalocean will think you want to leave, as a retention, Digitalocean will send e-mail to tempt you to stay, mail usually has a coupon code, let you use for free.Digitaloce

A lot of friends have encountered such a problem, that is: through the invitation of other people link, when they entered the student discount code on GitHub, but the prompt is not available. The reason is that the Digitalocean website limits the number of offers, which means that no matter how you get the offer, you can only offer it once, so the student code doesn't work. This time you can in the site s

). Sequences and mappings are two main types of containers. Python does not have a separate heap (data structure) type. There is only one module (HEAPQ) that contains some heap operation functions. The environment variable is not part of the Python interpreter, it belongs to the operating system.If you do not set the __all__,import* statement, the default import module has all the global names that do not begin with the underscore .Map () function and lambda (omit some unnecessary for loo

From: http://blog.csdn.net/maxleng/article/details/5472988 Concept Space of Methodology Discussion We do not want to use computers to think about problems. We have our own ways of describing our thinking. The closer we are to our way of describing our thinking, the easier we are to accept and use. A variety of computer languages and modeling tools are nothing more than creating a conceptual space that is closer to human thinking, and then using to

Such a simple article certainly cannot say all the benefits and essentials of the full MySQL 5.1 partitioning mechanism (although very confident in writing your own article level), here are a few interesting: Supports all storage engines (MyISAM, Archive, InnoDB, etc.) Indexes are supported on partitioned tables, including local indexes locally indexes, which is a one-to-two view mirror, assuming that a table has 10 partitions, its local index also contains 10 partitions. The table on the metad

Programming | program | programmer | object | concept If you've never used an object-oriented language before, you'll need to understand the concept before you start writing Java code. You need to understand what objects are, what classes are, how objects and classes are related, and how messages are communicated between objects. The previous section of this tuto

transmission. This combination is accomplished simply by using jobs as the input and output streams. These jobs are also decoupled: they do not need to be based on the same code library, and adding, deleting, or restarting a downstream task does not affect upstream tasks. Concept 6: partitions in the containers partition and task tasks are parallel logical units. They do not match the allocation of specif

scenarios, as well as the attribute level of lazy loading, Hibernate provides a good support, please refer to the relevant information hibnate.So far, I believe that everyone has a clearer understanding of VO, DTO, do, PO concepts, differences and practical application. Through the above detailed analysis, we can also summarize a principle: the analysis design level and the implementation level is completely two independent layers, even if the implementation level through a technical means can

Design Concept of FPGA Asynchronous FIFO (2) First, we will discuss the Gray code encoding method: Let's first look at the 4-bit gray code. When MSB is 0, the positive count is displayed. When MSB is 1, that is, the pointer has already passed through, and the highest digit is flipped. At this time, the gray

To Make It namenode. 3. HDFS federationnamenode stores the file and block information in the HDFS File System in the memory, which limits the memory resources when the cluster grows. Therefore, in hadoop 2. X introduces the HDFS Federation concept, allowing more namenodes nodes to expand the HDFS scale. Each namenode manages a namespace, for example, a namenode manages all files under/usr, another namenode

. In general, the real object should be to increase access restrictions, for example: not being able to access outside.When it comes to proxy mode, the JDK implements a dynamic proxy mode, why there is a dynamic proxy, because the above, although the implementation of the proxy, but each class A proxy, the code is bloated, and does not conform to the same function corresponding to a block or a class, or abstract package design

class, that is, a class can have only one parent class, and this restriction is called single inheritance. The concept of Interface (interface) is learned later, and interfaces allow multiple inheritance.Finally, the above code is organized: Public class Demo { public static void main(String[] args) { Teacher t = new Teacher(); T. Name = "cloth"; T. Age = ; T. School = "T

Density Storage server (1): Unscrupulous mix type") 6 Fully equipped 4U cages of 24 storage nodes, 12 pieces per node of Seagate's 3.5-inch 4T hard drive, capable of providing about 1.2 PB of physical storage space, using a three-copy strategy, a total of 384TB of storage capacity.Swift divides the storage node into zones and saves the copy to a different zone, in general, the number of zones should be greater than or equal to the number of replicas.Zone division principle for physical fault is

to use effectively;2. SecurityFor most people, the situation is almost always met (computer or mobile phone). The evil operators or network access WiFi providers hijack our network, modify the content of the network, has brought us a lot of trouble;Two. http/2.0Now, Http/2.0 has appeared. In fact, http/2.0 is supported Clear Text version and Over TLS version, because the existing support Http/2.0 browser is implemented over TLS version, so this artic

ObjectiveIn the example code of the previous article, you must have found the observable class. From a pure Java perspective, the observable class derives from the Classic observer pattern. The asynchronous implementation of Rxjava is based on the observer pattern and is an extended observer pattern.Observer patternThe Observer pattern is based on the concept of subject, subject is a special object, also ca

example, is the ability to compile Java code into corresponding machine code sequences based on different machine architectures. Thus realizing the cross-platform of Java's "one compile, run everywhere".Having said the values and characters, let's talk about the mathematical characteristics of binary.The computer stores the data using binary, which is very similar to the "Boolean algebra" in mathematics. I

function is $ $f (x) = E^{-\lambda}{\lambda^x\over x!},\ x=0, 1, 2, \cdots$$ the expected Valu E is $$\mu= \lambda=10$$ and the standard deviation are $$\sigma = \sqrt{\lambda} = 3.162278$$ the probability that $X $ ta Kes A value more than-deviations from $\mu$ is $$ \begin{align*} p\left (| x-\lambda| \geq 2\sqrt{\lambda}\right) = p\left (x \leq \lambda-2\sqrt

, language often denotes a quot program language, which is used to programmatically implement functions and applications, but not all languages are programmed, and XML is just a language used to define identity and descriptive information. Let's take a closer look at the XML application of this principle, may be very boring, but for the overall understanding is very important, you can go through it quickly, the mind has a vague concept, the specific e