(I have written many Java programs and developed many Java projects, but now I decide to write a series of articles related to Java. Because I have no absolute confidence in my articles, they are all based on experience in the development process. In addition, I have taken the SCJP certificate before, so I hope to write more detailed articles that will not mislead the readers. So I hope some readers leave my email address to me if they think there is a clerical error, In addition, in order not to mislead the readers, the [draft] has been used. Thank you for your cooperation)