Generic method to convert List<CustomObject> to Chunk<CustomObject>

Question

I need a java method to convert Generic List of objects to Chunk.

e.g. from List<CustomObject> to Chunk<CustomObject>

The changes i have done below :

Change-1: (Working)

public static Chunk<CustomObject> convertListToChunk(List<CustomObject> listObject) {
    
    
    Chunk<CustomObject> chunkObject =  new Chunk<>(listObject);
    return chunkObject;
}

Change-2: (Not working)

public static Chunk<? extends Object> convertListToChunk(List<? extends Object> listObject) {
    
    
    Chunk<? extends Chunkable > chunkObject =  new Chunk<>(listObject);
    return chunkObject;
}

In this case we can also use BaseCustomObject like Chunk<? extends BaseCustomObject> where BaseCustomObject is super class of all custom object

Calling converter Method

List<CustomObjectX> finalList = new ArrayList<>();
Chunk<CustomObjectX> chk = convertListToChunk(finalList)

here CustomObjectX is any type custom object, or extends BaseCustomObject

Answer 1

Chunk<?> is short for Chunk<? extends Object> - hence, writing that out is meaningless.

You're looking for:

public static <W> Chunk<W> convertListToChunk(List<W> list) {
  return new Chunk<W>(list);
}

Which seems useless. This method already exists. It's... new Chunk<>(list);.

Generics serves to link things. Here, you want to link the the list's component type to the chunk's type. Declare a variable (<W> declares it), then use it in at least 2 places (because generic variables used only once are either useless, or some hackery; either way not a good idea generally).