Java NullPointerException

Of all the RuntimeExceptionexceptions, Java programmers are probably most familiar with NullPointerException. NullPointerException is the null pointer exception, commonly known as NPE. This exception is usually thrown by the JVM if an object is null called, its methods are called or its fields are accessed , for example:NullPointerException The concept of pointers is actually derived Read more…

How to use Log4j

Commons Logging was introduced earlier, which can be used as a “log interface”. And the real “logging implementation” can use Log4j. Log4j is a very popular logging framework, the latest version is 2.x. Log4j is a component-based log system, and its architecture is roughly as follows: When we use Log4j to Read more…