Java convert list to array

We can use Arrays.asList() to init an array with values. This page will show you how to convert List to T[]. For example convert List to String[]. The code is here.

Java determine thread pool size

You may have used ThreadPoolExecutor to submit some task and waiting for the result. In this way program can get the better performance. The question is how to calculate the size of pool size, in other words how to make CPU 100% or close to 100% busy?

Java8 add log in stream

Stream in Java8 can help us make code clear and efficient. We can use Stream to iterate a collection without the keyword for. It is very convenient. The question is how to print the information of item in a stream? In this page I will show you how to add log in stream. JDK provides peek function for debugging.

MyBatis Spring example

In this page I will show you how to integrate MyBatis and Spring. I use maven to build the project. The structure of the project is like following.

MySQL dump create table sql

We can use show create table to show the create table sql. The best way to export the create table sql is using mysqldump command. Using following command to dump create tables sql of all tables in the test_db database.

Java generate random 6 digits number

There are different ways to generate random 6 digits. I recommend you to use RandomUtils or RandomStringUtils in apache-common-lang3 framework to generate it. Here is the sample code.

Maven change project version

Let's say you have a project and there are some module in it. If you want change the version of this project you can find all version number in global search and replace with new version or use following command.

Access angular app running on virtual machine

I install Node.js and npm in my virtual machine which OS is CentOS. I following official website here to start my first Angular app. After execute ng new my-app init the project I execute ng serve --open to start the app. The log is here.

Install Node.js in CentOS

Download Node.js Linux Binaries (x86/x64) from here. I use wget to download it.

rm Argument list too long

When I use rm *.log -rf to delete the files I got the following error message.

git config user name email

Use following command to add user name and email.

git enable color output

The default output of git is without color. Add following config in ~/.gitconfig can enable the git color output in your terminal. If there is not .gitconfig file create one.

Java8 Collectors.partitioningBy example

Collectors.partitioningBy is used to divide stream into two map. The key of two group are true and false. Two list of values are collections of elements that satisfy the condition. The example code is here.

Linux curl command examples

curl is a good tool to help you make a request. Before introducing how to use it we need to start a server which receives the requests. I use Spring Boot as a simple server. The code is like following.

Java8 stream groupingBy example

When we want to group the list data, we have to write some tedious code in the old version of the JDK. For example we want to group list of people by age. The code is like this before JDK8.