Idea after you create a MAVEN project, you cannot create a Java file in the file directory

Idea after you create a MAVEN project, you cannot create a Java file in the file directory

Today I created a MAVEN project with idea but found that it was not possible to create a. java file in a directory folder, such as figure: workaround

Right-click to select Mark directory as on the directory where you want to create the Java file, and then select the blue icon Sources Root to create the Java file when the folder you selected becomes blue. As shown in the final effect

If the tag error can be checked again by right-clicking the directory, then mark directory as, you will find an option unmark Sources root, and the tag directory will revert to its original status when selected.