"Cannot create generic array of .." - how to create an Array of Map<String, Object>?

Because of how generics in Java work, you cannot directly create an array of a generic type (such as Map<String, Object>[]). Instead, you create an array of the raw type (Map[]) and cast it to Map<String, Object>[]. This will cause an unavoidable (but suppressible) compiler warning.

This should work for what you need:

Map<String, Object>[] myArray = (Map<String, Object>[]) new Map[10];

You may want to annotate the method this occurs in with @SuppressWarnings("unchecked"), to prevent the warning from being shown.

You can create generic array of map.

1. Create a list of maps.

   List<Map<String, ?>> myData = new ArrayList<Map<String, ?>>();

2. Initialize array.

   Map<String,?>[] myDataArray = new HashMap[myData.size()];

3. Populate data in array from list.

   myDataArray = myData.toArray(myDataArray);

I have had some difficulty with this, but I have figured out a few things that I will share as simply as possible.

My experience with generics is limited to collections, so I use them in the class definitions, such as:

public class CircularArray<E> {

which contains the data member:

private E[] data;

But you can't make and array of type generic, so it has the method:

@SuppressWarnings("unchecked")private E[] newArray(int size){    return (E[]) new Object[size];  //Create an array of Objects then cast it as E[]}

In the constructor:

data = newArray(INITIAL_CAPACITY);  //Done for reusability

This works for generic generics, but I needed a list that could be sorted: a list of Comparables.

public class SortedCircularArray<E extends Comparable<E>> { //any E that implements Comparable or extends a Comparable class

which contains the data member:

private E[] data;

But our new class throws java.lang.ClassCastException:

@SuppressWarnings("unchecked")private E[] newArray(int size){    //Old: return (E[]) new Object[size];  //Create an array of Objects then cast it as E[]    return (E[]) new Comparable[size];  //A comparable is an object, but the converse may not be}

In the constructor everything is the same:

data = newArray(INITIAL_CAPACITY);  //Done for reusability

I hope this helps and I hope our more experienced users will correct me if I've made mistakes.