java package into your question

In a recent study found that some of the classes final modification java.lang used , without introducing package name , is not modified with the final class , not duplicate, can not be rewritten, it can be directly used , and that the bag with the other final modification is the introduction of package may not directly use it ? New learning , please guide , thank you !
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java.lang are not under the guidelines, the default has been introduced
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lang package under the No, the other was the introduction of
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+1