Java Coding Problems

Example 2 (computeIfAbsent())

Let's suppose that we have the following Map:

Map<String, String> map = new HashMap<>();map.put("postgresql", "jdbc:postgresql://127.0.0.1/customers_db");map.put("mysql", "jdbc:mysql://192.168.0.50/customers_db");

We use this map to build JDBC URLs for different databases.

Let's assume that we want to build the JDBC URL for MongoDB. This time, if the mongodb key is present in the map, then the corresponding value should be returned without further computations. But if this key is absent (or is associated with a null value), then it should be computed based on this key and the current IP and be added to the map. If the computed value is null, then null is the returned result and the map remains untouched.

Well, ...