类型无法创建List的通用数组<FooClass>

Question

Suppose I have class FooClass.

public class FooClass {
}

The following line gives me the following compile error:

// Note I want to create an array of length 4 of Lists of FooClass
List<FooClass> runs[]=new List<FooClass>[4];

Cannot create a generic array of List<FooClass> ...

Would appreciate any help.

Answer 1

List collection is not the same as array :

// if you want create a List of FooClass (you can use any List implementation)
List<FooClass> runs = new ArrayList<FooClass>();

// if you want create array of FooClass
FooClass[] runs = new FooClass[4];

UPD:

If you want to create array of lists, you should:

1. Create array
2. Fill this array in with List instances

Example:

List<FooClass>[] runs = new List[4];
for (int i = 0; i < runs.length; i++) {
    runs[i] = new ArrayList<>();
}

Answer 2

It's not good idea to mix Generics and Array. Generics doesn't retain type information at run time so creating an array of generics fails.

Answer 3

List should not be declared as array. It should be:

List<FooClass> runs=new ArrayList<FooClass>(4);

or

List<FooClass> runs=new ArrayList<FooClass>();

Edit : you can try List<ConfigParser> runs[] = new List[4]; . But why do you need array of Lists?

Also as @rai.skumar has mentioned, Generic information is not retained during run time because of Type Erasure.