How to create a guaranteed unique name in Java, file name

------------I do not have him, but the hand is ripe, humble and foolish, and eager to be hungry-------------

This blog has to say, how to create a unique file name , create a unique string string Why create a unique ? In many cases, such as file upload , filename should be inconsistent , otherwise covered out , how inconsistent, this is the content of this blog to speak

Note: It is foolish to use random numbers directly, and it will have the same number in a very large probability . Way One: time stamp

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Cause: timestamps may occur in high concurrency scenarios with the same

Solution: re-spell the random number, pay attention to stitching when you don't let two do addition time stamp variable + "" + Random number variable

        // time stamp the first kind        System.out.println (new  Date (). GetTime ());         // time stamp The second kind        System.out.println (System.currenttimemillis ());

　　Random number :

        // generate six-bit random numbers        SYSTEM.OUT.PRINTLN ((int) ((Math.random () *9+1) *100000));

mode two: microsecond number

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Reason: It is more granular than time stamp and has stronger control

　　You can also add random numbers or join your own rules.

        // number of microseconds        System.out.println (System.nanotime ());

Way Three:UUID

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Cause: He's a java.util under the bag. A class that can produce different character variables, it's very powerful.

        // the method of using UUID to                    import Java.util.UUID;        UUID Randomuuid = uuid.randomuuid ();        System.out.println (randomuuid);

mode four: customize the rules on top three basis

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Reason: In the daily three kinds are enough to meet their own small demo, small project use, but in the mature big project, perhaps some not enough to see, so, I said fourth kind

Idea: The file name is not a string, do the three sides of the stitching three ways any kind of time , you can add their own rules, such as the uploader ID, such as you upload from the explanation, even add 8 or more random numbers, etc.

is to customize the rules to make the probabilities smaller !!!!!!!!!

How to create a guaranteed unique name in Java, file name