Thank you @Lokesh_Vajrala,
The snippet is clear about getting the assets, now I got the asset map like
{
/content/dam/asset1.xls=com.day.cq.dam.core.impl.AssetImpl@abcd1234,
/content/dam/asset2.pdf=com.day.cq.dam.core.impl.AssetImpl@abcd1234,
/content/dam/asset3.PNG=com.day.cq.dam.core.impl.Asse...