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I am trying to implement bucket sort and I want to create an arraylist for each index of an array. I want to do something like this:

int bucket[]=new int[max+1];
for(i=0;i<=max/5;i++)
{
    bucket[i]=new ArrayList<Integer>();
}

But the above code doesn't work and throws an error. It states "generic array creation".I know that generic array types are not allowed in java but I can't understand where generic types comes here I mean something like or .I also want to know is there a way to cast Integer to int while creating the ArrayList I hope doing so will fix this.

share|improve this question
    
You don't need to specify the size of an array list. ArrayList<Integer>[5] just ArrayList<Integer>() –  Jorge Campos 2 days ago
    
@JorgeCampos Yeah I know that but If I use that it says '] expected' –  user1613360 2 days ago
    
Candroid had catch the problem... I've missed the types.. –  Jorge Campos 2 days ago
    
bucket must be of type ArrayList<Integer>[] –  hoosssein 2 days ago
    
@user1613360 i have posted an answer tell me if it is not you are looking for..i will delete it. –  Deepanshu Bedi 2 days ago

1 Answer 1

up vote 1 down vote accepted

Your data types do not match...

You are trying to put an ArrayList<Integer> into a int[]. It cannot hold this type of data!

please reconsider what you want to have:

int[][]
ArrayList<int[]>
ArrayList<ArrayList<Integer>>
ArrayList<Integer>[]  <--- thi is not well-supported due to the way generics work

If you want higher performance, you should have a look at GNU Trove, and maybe use

ArrayList<TIntList>

which should use much less memory than ArrayList<ArrayList<Integer>>.

If your data size is fixed, you probably are looking for

int[][] bucket = new int[max+1][max/5+1];
share|improve this answer
    
I changed it.It doesn't help gives the same error and it's not an answer. –  user1613360 2 days ago
    
See the lower part. Your problem is that int[] bucket cannot hold ArrayList<Integer>, obviously. –  Anony-Mousse 2 days ago
    
Can you please explain why? –  user1613360 2 days ago
2  
Because it can hold int only. Not ArrayLists. It's an array-of-integers, not an array-of-ArrayLists-of-Integers. –  Anony-Mousse 2 days ago
    
I just wonder why you're using ArrayList<ArrayList<Integer>> instead of showing to use List<List<Integer>> list = new ArrayList<List<Integer>>(); –  Zhuinden 2 days ago

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