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Java HashMap of HashMap vs HashMap of String
by zz64 in Programming Languages

I am new to Java and i am currently rewriting a Perl code in Java.
In Perl i have a Hash of Hash like

$hashref->{index1}->{index2}->{index3} = $value;

In this i store the index1 , index2 , and index3 in 3 separate hashes along with above hash.
Also Index1 and index2 are of type long and index3 is String.

Now i want to rewrite t

loading data to hashmap<String, HashMap<String, HashMap<String,ArrayList<ClassOb>>>>
by Greenman in Programming Languages

I am trying to load data to hash map of hash map and i keep getting null pointer and not sure if i am doing the right thing.

I want my hash map to be based on three keys SalesAreaCode, year and product. I want to store the rest in arraylist. I want to pass sales area code , year and product and list all product such as customer, quantity , price related to these three keys:
I r

Android: I have an array of HashMaps, how to find a particular HashMap entry given a key that is within one of the HashMap entries?
by chorn in Programming Languages

I have an array of HashMaps, how to find a particular HashMap entry given a key that is within one of the HashMap entries?

For example, I have this:

ArrayList<HashMap<String, String>> bathroomList = new ArrayList<HashMap<String, String>>();

I also know a key within one of the array entries I want to find:


Java.util.HashMap — why HashMap extends AbstractMap and implement Map?
by Fenix Drakken in Programming Languages

why HashMap extends AbstractMap and implement Map ? is extending AbstractMap not sufficient, because AbstractMap implements Map?

How to store positional indexes and document id's in a Hashmap<Hashmap<ArrayList>>
by Vasiliy in Programming Languages

I have text files within a directory. What i need to do is;

---for each word in all files

---find positional indexes of each word within a file

---find each file that the word has passed

In order to do this;

HashMap<String, HashMap<Integer, ArrayList<Integer>>>

I want to use a structure as a

Convert HashMap.toString() back to HashMap in Java
by Verbal in Java

i am using HashMap in java. i put some key-value pair in the HashMap object and then i converted HashMap into an String using toString() method and pass to the another method that take an String and convert this String into HashMap object and retrieve the value with it's corresponding key.

Is it is possible to get the HashMap Object,please give me clear idea about.


Any simple Java way to pass parts of a hashmap to another hashmap?
by Kbotei in Java

For my trading program, a Merchant object has a qualities HashMap of enumerated Qualities with Boolean values.

public class Merchants {
private Map<Qualities, Boolean> qualities = new HashMap<Qualities, Boolean>();

I would like to give each Merchant object a further ratedQualities HashMap of True Qualities with Byte or Integer values repr

Adding an element to an a HashMap in an ArrayList of HashMap in Java
by Thomas Gueze in Java

I have a source HashMap in Java:

HashMap<String, Integer> keyWordFrequencies;

Storing keywords of various length. I want to traverse this HashMap and work out the lengths of the ngrams stored in the String part of the map which defines the text of each keyword.

With this data, I want to populate a target ArrayList of HashMaps:

Correct way to initialize HashMap and can HashMap hold different value types?
by mkmitch in Programming Languages

So I have two questions about HashMaps in Java:

What is the correct way to initialize a HashMap? I think it might be best in my situation to use:

HashMap x = new HashMap();

But Eclipse keeps suggesting that I use:

HashMap<something, something> map = new HashMap();

Which is better?

Performance of Treemap, Hashmap and Linked Hashmap?
by J.W. Mosley in Programming Languages

In Tree map- Elements are sorted
In Hashmap- Not sorted

So, If i consider get,add remove elements on above types. then which map should i use??

would be grateful for help.


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