How do i iterate a collection tat consists of hashmap values?

[shiniskumar]

Ive got a collection that is populated by some key/value pairs.
How can i iterate ie to get its each key/value pair?

[r035198x]

Ive got a collection that is populated by some key/value pairs.
How can i iterate ie to get its each key/value pair?

Do you have just a HashMap or a collection of HashMaps?

[shiniskumar]

Do you have just a HashMap or a collection of HashMaps?

collection of hashmaps added to a collection.
i wanna iterate tat collection to get each key/value pairs

[r035198x]

collection of hashmaps added to a collection.
i wanna iterate tat collection to get each key/value pairs

So have one hashmap with key-value pairs?

You can use the values method to get a collection view of all the values

[shiniskumar]

So have one hashmap with key-value pairs?

You can use the values method to get a collection view of all the values

actually my collection is an object[] which in which each element is a key/value pair.
eg it is an Object[1o] where
Object[0]=HashMap(k,v)
Object[1]=HashMap(k,v)
Object[2]=HashMap(k,v)........so on
Now how do i iterate this.

[r035198x]

actually my collection is an object[] which in which each element is a key/value pair.
eg it is an Object[1o] where
Object[0]=HashMap(k,v)
Object[1]=HashMap(k,v)
Object[2]=HashMap(k,v)........so on
Now how do i iterate this.

You can iterate arrays using a for loop. Then for each HashMap in the array you can use the values method on it and iterate through them

[dmjpro]

if u have collections of hashmap....

then try to iterate the collection first ......

while(obj.hasNext())
{
HashMap m = (HashMap)obj.next();
Collection c = m.values();
Iterator i = c.iterator();
while(i.hasNext())
{
Object value = i.next();
//Object key = m.get();
//I also face the problem here to extract a key from a value.
}
}

i think u also face the same problem as i face... m i right?????

plz anyone help ...........

thnaxxxx ......

[dmjpro]

i got the solution ......


while(obj.hasNext())
{
HashMap m = (HashMap)obj.next();
Set s = m.keySet();
Iterator i = s.iterator();
while(i.hasNext())
{
Object key = i.next();
Object value = m.get(key);
}
}

all the best ........

[r035198x]

Guys le't keep all code in code tags.

[dmjpro]

sorryyyyy ... again

[shiniskumar]

sorryyyyy ... again

oops sorry for tat

[dmjpro]

actually i again again forget to quote the code .....that's why i m sorrryyyyy

[itsraghz]

two more ways you can do is..


(i) use the keySet() method which would give you the set of keys in the Collection.

public void testKeySet(HashMap hashMap)
{
Set keySet = hashMap.keySet();
Iterator keySetIterator = keySet.iterator();
while(keySetIterator.hasNext())
{
Object key = keySetIterator.next();
Object value = hashMap.get(key);
System.out.println("key="+key+",value="+value);
}
}
 

Note: TypeCast the Key,Values accordingly as how the hashMap was prepared [to avoid classCastException at runtime in your applications].

Here for the purpose of demo, i have directly used java.lang.Object to deal with them both.


(ii) use the entrySet() method which is more or less the same as values() method but it returns a java.util.Set() instead of java.util.Collection object. In both ways, you can obtain an iterator from the returned objects and then proceed with iterator.next() with proper typecastings.


Hope this helps...

[shiniskumar]

two more ways you can do is..


(i) use the keySet() method which would give you the set of keys in the Collection.

public void testKeySet(HashMap hashMap)
{
Set keySet = hashMap.keySet();
Iterator keySetIterator = keySet.iterator();
while(keySetIterator.hasNext())
{
Object key = keySetIterator.next();
Object value = hashMap.get(key);
System.out.println("key="+key+",value="+value);
}
}
 

Note: TypeCast the Key,Values accordingly as how the hashMap was prepared [to avoid classCastException at runtime in your applications].

Here for the purpose of demo, i have directly used java.lang.Object to deal with them both.


(ii) use the entrySet() method which is more or less the same as values() method but it returns a java.util.Set() instead of java.util.Collection object. In both ways, you can obtain an iterator from the returned objects and then proceed with iterator.next() with proper typecastings.


Hope this helps...

my collection on expanding becomes

ArrayList<E> "voucherTransactionCols"= ArrayList<E>  (id=122)
    E[] elementData= Object[10]  (id=133)
        Object [0]= HashMap<K,V>  (id=135)
        Object [1]= HashMap<K,V>  (id=137)
            Set<Entry<K,V>> entrySet= HashMap$EntrySet  (id=150)
            Set<K> keySet= null
            float loadFactor= 0.75
            int modCount= 2
            int size= 2
            HashMap$Entry<K,V>[] table= HashMap$Entry<K,V>[16]  (id=151)
                HashMap$Entry<K,V> [0]= null
                HashMap$Entry<K,V> [1]= null
                HashMap$Entry<K,V> [2]= null
                HashMap$Entry<K,V> [3]= null
                HashMap$Entry<K,V> [4]= null
                HashMap$Entry<K,V> [5]= null
                HashMap$Entry<K,V> [6]= HashMap$Entry<K,V>  (id=152)
                    int hash= 361649174
                    K key= "liability"
                    HashMap$Entry<K,V> next= null
                    V value= "A"
                HashMap$Entry<K,V> [7]= null
                HashMap$Entry<K,V> [8]= HashMap$Entry<K,V>  (id=153)
                    int hash= -1446859816
                    K key= "lamount"
                    HashMap$Entry<K,V> next= null
                    V value= ""
                HashMap$Entry<K,V> [9]= null
                HashMap$Entry<K,V> [10]= null
                HashMap$Entry<K,V> [11]= null
                HashMap$Entry<K,V> [12]= null
                HashMap$Entry<K,V> [13]= null
                HashMap$Entry<K,V> [14]= null
                HashMap$Entry<K,V> [15]= null
            int threshold= 12
            Collection<V> values= null
        Object [2]= HashMap<K,V>  (id=138)
        Object [3]= HashMap<K,V>  (id=139)
        Object [4]= HashMap<K,V>  (id=140)
        Object [5]= null
        Object [6]= null
        Object [7]= null
        Object [8]= null
        Object [9]= null
    int modCount= 5
    int size= 5
 
 
 

on doing the following iteration i get

for (Iterator iter = voucherTransactionCols.iterator(); iter.hasNext();) {
                        Object object = (Object) iter.next();
                        HashMap campusModel = (HashMap) object;
                        Set keySet = campusModel.keySet();
                        Iterator keySetIterator = keySet.iterator();
                        Object key = keySetIterator.next();
 

but i get key as "lamount" and value as "".
i want to gert key as "liabilty" and value as "A".
how do i do tis?