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Question

I have a map as shown below in which there is a key and values is of type List :

Map<String, List<String> newdatamap = new HashMap<>();
map.put ("payerName", Arrays.asList("wpn", "wpfnb", "dgeft", "xbthy"));
map.put ("fixedRate", Arrays.asList("dd", "ww", "trrty", "httyure"))

I'd like to add another map over the previous map, such that there is a key and its value will be the above map. Is this the correct data structure, and how do we implement it?

I want something like this shown below

Key         Value

B1          payerName  ----> "wpn", "wpfnb", "dgeft", "xbthy"
            fixedRate ----->"dd", "ww", "trrty", "httyure"



B2          payerName  ----> "SSSwpn", "wpfSSSnb", "GGGdgeft", "xbtYYYYhy"
            fixedRate ----->"WWdd", "wTTYw", "YYYYtrrty", "IIIhttyure"

As shown above, only a new key is been introduced to the map, and its value is the previous map. Is a Map data structure the correct way to go about this, or do any other data structures work better?

Folks please advise as suggested in answers also will guava library will support JDK 1.5 also

Answer 1

From what it reads like...you want a Map<String, Map<String, List<String>>> .

It's easy enough to declare...

Map<String, Map<String, List<String>>> values = new HashMap<>();

...but not enjoyable to index into:

// get B2's fixed rates
values.get("B2").get("fixedRate");

Perhaps instead you should consider Guava's Table class instead. It will give you clear coordinates to what object you want to get, as well as preserve the overall structure you have.

final Table<String, String, List<String>> values = HashBasedTable.create();
values.put("B1", "payerName", Lists.newArrayList("wpn", "wpfnb", "dgeft", "xbthy"));
System.out.println(values.get("B1", "payerName")); // prints the list