How to convert a list object to a Map and iterate through Map

Let us consider we have a list object named usersList, now our requirement is to convert this list object into map and iterate through the map.

Each List object is nothing but a row in the database table

We can understand this better with an example

for (Map<String, Object> map : usersList) {

JSONObject jsonObject = new JSONObject();

for (Map.Entry<String, Object> entry : map.entrySet()) {

String key = entry.getKey();

Object value = entry.getValue();

if(“PRODUCT_NAME”.equals(key)){

//product name is name of the coloumn in the database

jsonObject.put(“productName”, value);

}

else if(“CONTRACT_STATUS”.equals(key)){

jsonObject.put(“contractStatus”, value);

}

Here the iteration through the list means iterating through reach row

i.e

List—>L[0]—->Row—>C[0],V[0]  (coloumn,Value)

C[1],V[1]

C[3],V[3]

Iterating through map takes place by iterating through each column of database and its corresponding value for that particular row in the list

Map—>M[0]—–>coloumn–>C[0],V[0]

M[1]———————->C[1],V[1]