Finally i found solution of how to get information of purchased item if it is already purchased or not
// subscriptions we own
IabHelper.QueryInventoryFinishedListener mGotInventoryListener = new IabHelper.QueryInventoryFinishedListener() {
public void onQueryInventoryFinished(IabResult result,
Inventory inventory) {
if (result.isFailure()) {
complain("Failed to query inventory: " + result);
return;
}
mIsPremium = inventory.hasPurchase(SKU_PREMIUM); ------> By here you can get information
}
};