Error analysis:

First of all, read the reason for the error. The error message shows that the project SDK is not defined. It prompts me to install the SDK. Some novice friends are a little confused at this time. They only know that JDK is a java development kit. So what is the SDK? I have never used it before. How can I prompt me to install it at this time. At this time, don’t worry, guys. In fact, SDK refers to the software development kit (abbreviation: SDK, full name of foreign language: software development kit). It is generally a collection of development tools used by some software engineers to build application software for specific software packages, software frameworks, hardware platforms, operating systems, etc. here, SDK refers to our JDK, that is to say, this The project could not find the dependent JDK. At this time, we go to check the project environment configuration and find the following situation:

Sure enough, there is a problem with the JDK environment configuration, and then the problem is solved by choosing our JDK environment path.