多谢！第三个是可以，不过还是有
Note: aaa.java uses unchecked or unsafe operations
难道就没有办法可以避免吗？
Leave it
this warning message just shows that compiler cannot assure correctness of this casting operation as clone() method returns type of object.
It is really programmer's responsibility to avoid any casting failure.
It is really programmer's responsibility to avoid any casting failure.
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