Introduction to Amazon DynamoDB 6: query and scan

In the previous section, we introduced the creation and management of DynamoDB indexes. In this section, we will introduce the use of query and scan. Query Query SQL can use SELECT statements to query key columns, non-key columns, or any combination. The WHERE clause determines the row returned. The DynamoDB Query operation provides fast and ef ...

Posted on Sun, 07 Apr 2019 07:51:31 -0700 by spxmgb

Implementation of left-slip deletion effect of Wechat applet

Reprinted from: http://www.jianshu.com/p/07c4ddf8a3d3 Today we will talk about the implementation of the left-slip deletion effect of the Wechat applet. Now many apps in the market are using this effect. When a listView page slides an item to the left, there will be a deletion or other option on the right. The user experience is very goo ...

Posted on Fri, 05 Apr 2019 23:09:30 -0700 by monkeybidz

The problem of reading and writing java files

File (memory) - - input stream - > program - - - output stream - > file (memory) When we read and write text files, it is very convenient to use Reader, such as FileReader, Input Stream Reader and Buffered Reader. The most important class is InputStreamReader, which is a bridge between bytes and characters. You can re-specify the encod ...

Posted on Thu, 04 Apr 2019 18:45:36 -0700 by willwill100

Introduction to ThreadPool Executor

1. Benefits of using thread pools The disadvantages of new Thread every time are as follows: Every new Thread new object has poor performance. Threads lack unified management, may create new threads unrestricted, compete with each other, and may occupy too much system resources leading to crash or oom. Lack of more functions, such as regular ...

Posted on Thu, 04 Apr 2019 17:15:29 -0700 by Vibralux

Reaction Anti-pattern - Dynamic Display of Asynchronous Components without Using jsx

Preface: anti-patterns refer to the coding mode that violates the react idea. In App component, this paper dynamically displays Model component through Model.show and realizes data interaction through Promise asynchronous form. This example includes 1. using jsx dynamic display components; 2. using this.props in getInitial State Code address: h ...

Posted on Thu, 04 Apr 2019 11:24:29 -0700 by Tuck

ACM Prepare for War

Rule taking https://vjudge.net/contest/292276#problem/D 2018 Beijing Cyber Competition Thoughts for solving the problem: /* There are n cities i n a circle, numbered 1-n. To reach the first city, it is necessary to spend ai gold coins and get bi gold coins. At the beginning, there are c gold coins. You can choose any city as ...

Posted on Wed, 03 Apr 2019 20:42:29 -0700 by alex_bg

Opencv2 Series Learning Notes 2 (Image Traversal)

There are three main methods of image traversal. This section mainly introduces and compares these three methods. One: Simple access to pixel values First, we introduce a noun, salt and pepper noise: it is a special noise point, which randomly sets some of the pixels in the image to white or black. Code: #include <ope ...

Posted on Wed, 03 Apr 2019 13:27:30 -0700 by kind

Opencv2 Series Learning Notes 6 (Histogram Application)

I described the concept of histogram and how to use opencv to realize one-dimensional and two-dimensional histograms. See these two blog: Mat formats for details: http://blog.csdn.net/lu597203933/article/details/16884409   cv: http://blog.csdn.net/lu597203933/article/details/14104505  This time, I mainly want to talk about the applicati ...

Posted on Wed, 03 Apr 2019 13:06:29 -0700 by Negligence

Merge multiple arrays of different lengths according to rules

Existing multi-array integer arrays need to be merged into a new array. Merge Rule: Take the fixed length content from each array in order and merge it into a new array. The finished content should be deleted. If the change line is less than the fixed length or has been empty, take the rest of the content directly into the new a ...

Posted on Wed, 03 Apr 2019 11:33:29 -0700 by gnize

Life Cycle Testing and Conclusion of Activity in Equipment Rotation

There are many similar articles on the life cycle of Activity when Android handsets switch between horizontal and vertical screens. Most of them show that Activity will restart once when the vertical screen is switched over, and Activity will restart twice when the vertical screen is switched over. I don't quite understand the meaning of this d ...

Posted on Wed, 03 Apr 2019 00:09:29 -0700 by socratesone