[Java adds and verifies PDF digital signature]

Among the methods for setting up document content protection, in addition to encrypting documents and adding watermarks, applying digital signatures is also an effective means of document anti-counterfeiting and protection. Digitally signed documents are easy to verify and have high authority and credibility. In Adobe PDF documents, there are functions and methods to directly add […]

An explanation of transaction isolation and other concurrent transactions in MySQL database

In MySQL, the transaction isolation level defines the situation in which a transaction and other concurrent transactions can see each other’s changed data. The SQL standard specifies four isolation levels, as follows: Serialization (SERIALIZABLE): Transactions are executed serially, that is, each transaction must wait for the end of the previous transaction before starting execution. This […]

Comprehensive explanation of Java regular expressions and various sample codes

In-Depth Guide to Java Regular Expressions Introduction Regular expressions are a powerful text matching tool that are widely used for operations such as string search and replacement. In Java, the use of regular expressions involves the Pattern and Matcher classes. This article aims to provide a more in-depth perspective, detailing the various symbols and patterns […]

Golang os package: process creation and termination, running external commands

The os package and its subpackage os/exec provide methods for creating processes. Generally, the os/exec package should be used first. Because the os/exec package relies on the key process creation APIs in the os package, for ease of understanding, we first discuss the process-related APIs in the os package. part. Creation of process In Unix, […]

[Distributed] tensorflow 1 distributed code practice and explanation; running 2 distributed worker threads on a single node

tensorflow.python.framework.errors_impl.UnknowError: Could not start gRPC server 1. tf distributed A computer = server = server is a node that contains multiple GPUs. First of all, the distributed method is to let the GPUs on multiple computers work together. Distributed work is divided into two parts, parameter server (ps) and worker. PS and worker look familiar, […]

A brief explanation of the use of List [C++]

A brief explanation of the use of List [C++] 1. List 1.1. Difference from vector 1.2 Different from the use of vector 1.2.1 Iterator invalidation 1.2.2. insert 1.2.3 erase 1.2.4 sort 1.3. Other interfaces Supplementary iterator The relationship between containers and iterators Iterator type 一. List After learning STL, I have also reached the content […]

[Data structure] Sequential stack and chain stack (detailed explanation with diagram)

Article directory 1. What is a stack? 1.1 Purpose of stack 2. Stack structure and basic operations 3. Implementation details of the stack 3.1 Sequential stack 3.1.1 Stack initialization 3.1.2 Pushing elements onto the stack 3.1.3 Pop elements from the stack 3.1.4 Get the top element of the stack 3.1.5 Determine whether the stack is […]

Data Structure-Linear Table-In-depth explanation

Linear table Array Concept: An array (Array) is an ordered collection composed of a limited number of variables of the same type. Each variable in the array is called element. Array subscripts start from zero. Arrays use a contiguous memory space to store a set of data of the same type. Time complexity: Reading and […]