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javaarrayslist
Chet
Chet

Reputation: 1269

List of Arrays in Java

What is the syntax for making a List of arrays in Java?

I have tried the following:

List<int[]> A = new List<int[]>();

and a lot of other things.

I need to be able to reorder the int arrays, but the elements of the int arrays need not to be changed. If this is not possible, why?

Thank you.

Upvotes: 37

Views: 122499

Answers (3)

gprathour
gprathour

Reputation: 15333

Firstly, you can't do new List(); it is an interface.

To make a list of int Arrays, do something like this :

List<int[]> myList = new ArrayList<int[]>();

P.S. As per the comment, package for List is java.util.List and for ArrayList java.util.ArrayList

Upvotes: 71

Woot4Moo
Woot4Moo

Reputation: 24316

List<Integer[]> integerList = new ArrayList<Integer[]>();

Use the object instead of the primitive, unless this is before Java 1.5 as it handles the autoboxing automatically.

As far as the sorting goes: 

Collections.sort(integerList); //Sort the entire List

and for each array (probably what you want)

for(Integer[] currentArray : integerList)  
{  
    Arrays.sort(currentArray);  
}

Upvotes: 9

Tom
Tom

Reputation: 1221

List is an interface, not a class. You have to choose what kind of list. In most cases an ArrayList is chosen.

List a = new ArrayList();

You've mentioned that you want to store an int array in it, so you can specify the type that a list contains.

List<int[]> a = new ArrayList<int[]>();

While you can have a collection (such as a list) of "int[]", you cannot have a collection of "int". This is because arrays are objects, but an "int" is a primitive.

Upvotes: 6

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