Eclipse包需要成功运行

Question

I'm just beginning at running simple Java programs with Eclipse. The udemy.com tutorial I'm working from starts each program with public class followed by the main method. I get an error in main method compilation error, unless I start a file from scratch and include the package line at the beginning. It runs fine when package is included. I don't understand why this is necessary. Most of the tutorials and example code I've looked at do not include the package line.

Answer 1

Many tutorials skip parts of the code for the sake of brevity, such as the package declaration and imports. However, the package should ALWAYS be declared at the top of the class if the class is inside of a package inside your source directory. The only time you don't declare the package is if the class is directly inside your source directory (considered the default package). However as the comments mention - this is not a very good practice. Also, you shouldn't need to start a file from scratch - just add the package declaration at the top and save the file - which should trigger a compile. If it doesn't - make sure you have Project > Build Automatically enabled.