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.
Here is my own common vim configuration. Disable syntax and enable spell check in markdown file.
Add following function in your ~/.bashrc file then you can use one command to commit changes and push them to remote.
reduce method of stream is used to calculate elements in the stream and get the result. For example, we can use reduce to get the sum of Integer list. It can also help you to get the min or max number of Integer list.
map method is used to handle the element of stream and output the stream. flatMap method is used to handle multiple stream and output new stream. Here is some easy examples.
When I run mvn clean install -DskipTests to build my project I got an error message. The content of message is like following.
Nginx will add Content-Type depend on suffix of url in response header. The suffix and Content-Type mapping are in /etc/nginx/mime.types. There are two ways to change Content-Type in Nginx.
When I run Spring Boot jar in different environment I need different configuration. I use command line to assign the location of application.properties. Let's say you have a project without application.properties file and you package it as jar. You can use java -jar YOUR_PACKAGE_NAME.jar to start this project. The output is like following.
I install CentOS in virtualBox and I use Bridged Networking to connect internet. Virtual machine is like a real machine in bridged networking mode. The problem is that when I restart virtual machine the ip will be changed. I have to use ssh to reconnect virtual machine(CentOS). To solve this problem I add another network adapter in virtual machine with Host only mode. Finally, I can connect virtual machine by static ip address.
Let's say you have a file which contains log content. awk command can help you split every line of it and print the field you care about. awk can do more than this. Let's say your log file might look like this.
I always use cron expression to execute scheduling task. I want to know when the task will be executed. I use CronSequenceGenerator to calculate the next run time which is a class of Spring Framework. The example code is here.
It is easy to use log4j2 in spring boot. Create a maven project, structure like following.
I installed VirtualBox in my computer and installed CentOS in it. When I need Linux environment I start VirtualBox and use ssh(XShell) to connect it. It's boring to start VirtualBox by click Start menus every time. I write a bat script to run VirtualBox in the background. It seems like this.
In this page I will show you how to sort a stack by using a temporary stack. The key step of sorting is make sure that push items into temporary stack in order. The code is here.
The key step of reversing stack by using recursion is implementing the method popBottom. If we can pop an item from bottom of stack, then we can reverse a stack with two items.