Programmer Group

The creation operators in RxJs are the starting point of creating data flow. These operators can create a flow out of nothing or according to other data forms. The Observable constructor can directly create a data flow, such as: const $source=new Observable(observer=>{ observer.next(1); observer.next(2); observer.next(3); }) H ...

[directory] 1, Introduction to formal parameters and actual parameters II. Specific use of formal parameters and actual parameters 2.1 location parameters 2.2 key parameters 2.3 default parameters 2.4 variable length parameters (* and * * usage) 2.4.1 variable length position parameters 2.4.2 variable length key parameters 2.5 named ...

Source code analysis of HashMap (JDK1.8) This is one of the series that I forgot to read again. Today I have time to write a document and record it. I hope I can slowly understand their excellent ideas from the JDK source code. This paper mainly records the following aspects. 1. Inheritance and implementation structure of HashMap 2. Constructor ...

The original String type is so powerful, I just thought it was used to define a String. Next is a day to learn String type by doing homework.At the end of the article, there is the help document of JDK API 1.6 in Chinese. It is necessary for novices to get it for free! Brother, I have been looking for i ...

The main idea of the topic The headquarters generals plan to deploy their artillery units on the NM grid map. An NM map is composed of N rows and M columns. Each grid of the map may be mountainous (represented by "H") or plain (represented by "P"), as shown below. At most one artil ...

This article will build a project in IDE and write corresponding code through the class diagram shown below. In practice, we will recognize the inheritance, aggregation, synthesis (combination), association, dependency of Java. After you finish this project, you will have a deep understanding of these r ...

1. Simple query statement (DQL) Syntax format: select field name 1, field name 2, field name 3 from table name; mysql> select ename,empno from emp; +--------+-------+ | ename | empno | +--------+-------+ | SMITH | 7369 | | ALLEN | 7499 | | WARD | 7521 | | JONES | 7566 | | MARTIN ...

Title Description A list is given. Each k nodes are flipped and the flipped list is returned. K is a positive integer whose value is less than or equal to the length of the list. If the total number of nodes is not an integral multiple of K, the remaining nodes will remain in the original order. Expla ...

We know that the Java running environment for Android devices with lower version (4.X and below, SDK < 21) is Dalvik virtual machine. Compared with the higher version, the biggest problem is that the first cold start takes a long time after installing or upgrading the update. This often takes tens of seconds or even minutes. Users have to fa ...

Recently, I looked at the knowledge of distributed locks. They are still used more in practice, because in the case of high concurrency, if they are not suitable for distributed locks, the data will definitely have problems, such as the problem of seconds killing commodity inventory in e-commerce pla ...