CODEWITHSUNDEEP
javaandroidarrayssortingcomparator
Cameron
Cameron

Reputation: 1612

Java: Sorting different types of arrays to one another

I need to sort an array based on the positions held in another array.

What I have works, but it is kinda slow, is there a faster/better way to implement this?

2 Parts:

Part1

int i = mArrayName.size(); 
int temp = 0;
for(int j=0;j<i;j++){
            temp = mArrayPosition.get(j);
            mArrayName.set(temp, mArrayNameOriginal.get(j));
        }

In this part, mArrayPosition is the position I would like the mArrayName to be in.

Ex.
input:
mArrayName= (one, two, three)
mArrayPosition = (2,0,1)

output:
mArrayName= (three, one two)

Part 2 

int k=0;
int j=0;
do{
    if(mArrayName.get(k)!=mArrayNameOriginal.get(j)){
        j++;
    }else{

        mArrayIdNewOrder.set(k, mArrayId.get(j)); 
            k++;
            j=0;
        }
    }while(k < mArrayName.size());
}

In this part, mArrayName is the reordered name array, mArrayNameOriginal is the original name array.

Ex.
mArrayName = (three, one, two)
mArrayNameOriginal = (one, two, three)

Now I want to compare these two arrays, find which entries are equal and relate that to a new array that has their rowId number in it.

Ex.
input:
mArrayId = (001,002,003)

output:
mArrayIdNewOrder = (003,001,002)

So then I will have mArrayIdNewOrder id's matching up with the correct names in mArrayName.

Like I said these methods work, but is there a faster/better way to do it? I tried looking at Arrays.sort and comparators but they only seem to sort alphabetically or numerically. I saw something like I can create my own rules inside the comparator but it would probably end up being similar to what I already have.

Sorry for the confusing question. I'll try to clear up any ambiguities if needed.

Upvotes: 0

Views: 498

Answers (3)

ThomasRS
ThomasRS

Reputation: 8287

If your order indexes are compact, i.e. from index 0 to size - 1, then just use an array and create the updated list afterwards? About something like

MyArray[] array = new MyArray[size];
for(int j=0;j< size;j++) {
   array[  mArrayPosition.get(j)   ] = mArrayName.get(j);
}

// create ArrayList from array

Upvotes: 0

user432209
user432209

Reputation: 20167

The best performance read I've found is Android's Designing For Performance doc. You are violating a couple of the "Android way" style of doing things that will help you.

You are using multiple internal getters inside each loop for what looks like a simple value. Redo this by accessing the fields directly.

For extra credit, post your performance comparison results! I'd love to see em!

Upvotes: 1

Lundberg
Lundberg

Reputation: 404

You could use some form of tuple, some class to hold both id and name. You'll just to have a java.util.Comparator that compares it accordingly, both elements will move together and your code will be cleaner.

This data structure might be convenient for the rest of your program... if not, just take things off it again and you're done.

Upvotes: 1

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