如何通过哈希随机化（在Java中）？

Question

I have ArrayList of Strings. I need to randomize it by "hash number". Example:

ArrayList: "Word", "Simple", "Another", "Demo" hash: 1234567

As a result of randomizing I want to receive say: "Simple", "Word", "Demo", "Another"

with other hash: 542345 I want to receive say: "Word", "Another", "Demo", "Simple"

But the requirements is that that when I always sort by this hash the randomizing order will always be THE SAME for that HASH.

Any suggestions? Adviscs?

Answer 1

You can shuffle a List using a Random object that you initialize with the hash.

Collections.shuffle( myList, new Random(12345) );

When the same hash is used to seed the Random object, the shuffle order should turn out the same.

Answer 2

使用“哈希”（无论什么意思）作为随机数生成器的种子？

Answer 3

You can do this:

value1 = "hello" --> value1.hashCode() = 99162322  
value2 = "hello" --> value2.hashCode() = 99162322

So, if you 'really' need to use a Hash, then you can iterate through the ArrayList, sum up all the hash values generated and save it.

Now, when you need to verify that the hash is same or not, again iterate through the new arraylist, generate the hashcode(), sum it up and check.

But it's an overkill. You can simply use shuffle() as suggested by Bill.