每个Java文件自动导入的library

每个Java文件自动导入的library

At the beginning of each program file, you must place any necessary import statements to
bring in extra classes you’ll need for the code in that file. Note that I say “extra”. That’s
because there’s a certain library of classes that are automatically brought into every Java file:
java.lang .

在每一个Java文件的开始，你都必须使用import关键词来将额外的class导入进来，注意我说的是额外的。这是因为对于每个Java文件，都会自动导入一个特定的library:java.lang