So many books, so little time.
As we all know, JVM will do garbage collection when there is not enough memory to use. You can use System.gc() in your code to trigger garbage collection. But when JVM does this is not uncertainty.
There are many ways to handle the exception in Spring Boot. You can click Spring Boot exception handler example or Spring Boot global exception example to see how to handle exception in controller or handler. I will show you how to handle exception by implementing HandlerExceptionResolver.
Let's say you have a list of string and you want to add separator to them. If you use JDK8+ you can use String.join(). For JDK7-, I recommend you to use StringUtils in apache-commons-lang. The code is like following.
Today I got NoClassDefFoundError when I test my new feature. The stack information is like following.
I have shown you how to handle exceptions in controller. Click here for more detail. You can use @ControllerAdvice to define a global handler. This handler is for handling global exceptions. The structure of this example project is like following.
Thymeleaf is a Java template engine. In this page I will show you how to use it in Spring Boot. You can use it to display the page. The structure of project is like following.
In this page I will show you how to use ExceptionHandler annotation handle exceptions. The structure of project is like following.
We use cat command to combine multiple files into one. Here are the examples. Let's say you have 3 files like following.
I have showed you how to convert object to pretty json in my previous blog. Today I will how you how to convert json string to pretty json. Before using writerWithDefaultPrettyPrinter method we need to convert json string to Object first then convert object to pretty json.
If there are more than one null elements in list list.remove() method can not remove all of them. Use list.removeAll() to remove them. Example code is like following.
Today I got the error message like following.
The visitor is the most complex design pattern. This pattern shows us how to "visit" the elements of one structure without changing the code of element's. Add a new visitor when you want to add a new operation for these elements.
In Java do not use float or double to do decimal arithmetic. Use BigDecimal instead of float and double. If you want to know the details click here.
After fresh installing CentOS and starting the system there is a sentence on the screen "Press any key to enter the menu, Booting boot in __seconds". Editing the /etc/grub.conf to remove the sentence and start CentOS quickly. The content is like following.