lambda expression in Python functional programming

Definition of anonymous functionlambda parameter_list: expressionTwo: ternary expression Result returned when the condition is true if the condition determines the result returned when else condition is falseThree: map map(func(arg1, arg2...), list1_arg1, list2_arg2), Perform the previous functions (mathematical mapping) on the list e ...

Posted by nando on Tue, 17 Dec 2019 13:36:42 -0800

Calculate the distance between two longitude points? (Haversine formula)

How to calculate the distance between two points specified by longitude and latitude? For clarity, I want the distance in kilometers; these points use the WGS84 system, and I want to know the relative accuracy of the available methods. #1st floor This is a simple PHP function that gives a very reasonable approximation (error range is ...

Posted by MFHJoe on Tue, 17 Dec 2019 01:56:12 -0800

How do I use reflection to call generic methods?

When type parameters are unknown at compile time, but are acquired dynamically at run time, what is the best way to call generic methods? Consider the following example code - inside the Example() method, what is the simplest way to call genericmethod < T > () using the Type stored in the myType variable? public class Sample { p ...

Posted by scottybwoy on Fri, 13 Dec 2019 03:56:12 -0800

synthetic: a trick of Java cold knowledge compiler

When we read the JDK reflection package source code, we will encounter the isSynthetic() method. One of its implementations is Modifier.isSynthetic(getModifiers()), and the principle of other methods is the same. Modifier is a special class for defining modifiers, among which static final int synchronous = 0x00001000 is one of the modifiers.I t ...

Posted by Tyche on Thu, 12 Dec 2019 00:17:29 -0800

New feature of Java 8 -- Lambda expression

I. Basic Introduction Lambda Lambda is a new feature introduced by java 8. A lambda expression is an anonymous function. It provides a Simpler Syntax and cooperation mode, which enables us to replace the functional interface by expression. Lambda expressions can be used to simplify the creation of anonymous inner classes. Functional interfa ...

Posted by lucidfx on Wed, 11 Dec 2019 10:10:44 -0800

Stream stream operation in Java

Preface In recent internship, I saw some codes of my predecessors in the company, and found that there are many places worth learning. One part of them is to use Stream stream operation for collection, which is very beautiful and convenient. So learn some Stream streams and record them here. What is Stream Stream is a new feature in Java 8, whi ...

Posted by Dark_Archon on Tue, 10 Dec 2019 11:10:17 -0800

Common data cleaning in Mongdb

Preface Share some common data cleaning methods of Mongdb Note: "Exceeded memory limit for $group, but didn't allow external sort. Pass allowDiskUse:true to opt in." causes and solutions: Reason During big data calculation and data statistics, each calculation task (job or task) will use independent and limited memory space. mongod ...

Posted by matbennett on Tue, 10 Dec 2019 09:59:48 -0800

Data Visual Analysis (Column, Line, Thermal)

1. Project introduction 1.1) Project Blog Address https://rpc.cnblogs.com/metaweblog/yyh28 1.2 Functions and Features of Project Completion Analyse the file''Jimei University Enrollment Score. xlsx''to complete the following functions: 1) The average scores of different provinces in this batch from 2015 to 2018 at Jimei University. The column c ...

Posted by fangorn on Mon, 09 Dec 2019 14:53:51 -0800

Thread learning note 2: worker threads in thread pool

This note is excerpted from: https://www.cnblogs.com/zhili/archive/2012/07/18/ThreadPool.html Record the learning process for future reference. I. thread pool Foundation First of all, it takes a lot of time to create and destroy threads. Second, too many threads also waste memory resources. Therefore, creating too many threads through Thread cl ...

Posted by dlkinsey85 on Mon, 09 Dec 2019 07:57:56 -0800

SimpleDateFormat Thread Security

background As we all know, SimpleDateFormat in Java is not thread-safe and can cause unexpected problems under multiple threads.This article will explore the specific reasons why SimpleDateFormat threads are insecure to gain a deeper understanding of thread security. Example Simple test code that can cause problems when multiple threads call th ...

Posted by Deany on Sun, 08 Dec 2019 08:22:33 -0800