HashMap in HashMap Doubts

[Micheal John]

Hi all,

I'm using HashMap to store data in key/value pair: below is what I'm doing..

HashMap h1 = new HashMap();
h1.put("01","Hello");
h1.put("02","World");
 
HashMap h2 = new HashMap();
h2.put("03","Hi");
h2.put("04","Tom");
 
HashMap h3 = new HashMap();
h3.put("100",h2);
h3.put("200",h3);
 
Iterator it = h3.keySet().iterator();
while(it.hasNext()){
   String key = (String)it.next();
   System.out.println("key :: "+key);
   System.out.println(h3.get(key));
}
 
o/p:
key :: 100
{01=Hello, 02=World}
 
key :: 200
{01=Hi, 02=Tom}
 
So.. Now it is in the form of 
key / value
100 / {01=Hello, 02=World}
 

I want to get for the key 100 and 01, the value is Hello
and 100 and 02, the value is World..

How to achieve this..is there any api for this..or we have to use like StringTokenzier..?

[Joanne Neal]

h3.get(key)

returns a HashMap, so just iterate through that the same way as you iterated thru h3.

[Edwin Dalorzo]

Do you mean somewhat like this?

Map<String,String> h1 = new HashMap<String,String>();
h1.put("01","Hello");
h1.put("02","World"); 

Map<String,String> h2 = new HashMap<String,String>();
h2.put("03","Hi");
h2.put("04","Tom"); 
 
Map<String,Map<String,String>> h3 = new HashMap<String,Map<String,String>>();
h3.put("100",h1);
h3.put("200",h2);

System.out.println(h3.get("100").get("01"));
System.out.println(h3.get("100").get("02"));
System.out.println(h3.get("200").get("03"));
System.out.println(h3.get("200").get("04"));

[Micheal John]

It's seems to be generics.. only supported in 1.5..? i am using i.4..?

[Paul Sturrock]

The logic will be the same though. 1.4 version:

Map h1 = new HashMap();
h1.put("01","Hello");
h1.put("02","World"); 
Map h2 = new HashMap();
h2.put("03","Hi");
h2.put("04","Tom");  
Map h3 = new HashMap();
h3.put("100",h1);
h3.put("200",h2);
 
System.out.println(h3.get("100").get("01"));
System.out.println(h3.get("100").get("02"));
System.out.println(h3.get("200").get("03"));
System.out.println(h3.get("200").get("04"));

[Micheal John]

Thanks paul, Edwin and also neal..

[Edwin Dalorzo]

The logic will be the same though. 1.4 version:

Did you not miss the casting, Paul?

System.out.println(((Map)h3.get("100")).get("01"));
System.out.println(((Map)h3.get("100")).get("02"));
System.out.println(((Map)h3.get("200")).get("03"));
System.out.println(((Map)h3.get("200")).get("04"));

[Paul Sturrock]

Yup Teach me for just regexing out the generics syntax...