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converting Arraylist to array

Posted on 2002-03-21
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How to convert Array List to Array?Can anyone explain with an example?


Thanks in advance
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Question by:Delphine_victorus
7 Comments
 
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by:bobbit31
ID: 6886254
ArrayList al = new ArrayList();

al.add("hello");
al.add("world");

String[] myArray = al.toArray();

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by:bobbit31
ID: 6886257
from javadocs:

toArray
public Object[] toArray()
Returns an array containing all of the elements in this list in the correct order.
Specified by:
toArray in interface List
Overrides:
toArray in class AbstractCollection
Returns:
an array containing all of the elements in this list in the correct order.

--------------------------------------------------------------------------------

toArray
public Object[] toArray(Object[] a)
Returns an array containing all of the elements in this list in the correct order. The runtime type of the returned array is that of the specified array. If the list fits in the specified array, it is returned therein. Otherwise, a new array is allocated with the runtime type of the specified array and the size of this list.
If the list fits in the specified array with room to spare (i.e., the array has more elements than the list), the element in the array immediately following the end of the collection is set to null. This is useful in determining the length of the list only if the caller knows that the list does not contain any null elements.

Specified by:
toArray in interface List
Overrides:
toArray in class AbstractCollection
Parameters:
a - the array into which the elements of the list are to be stored, if it is big enough; otherwise, a new array of the same runtime type is allocated for this purpose.
Returns:
an array containing the elements of the list.
Throws:
ArrayStoreException - if the runtime type of a is not a supertype of the runtime type of every element in this list.
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Venci75 earned 10 total points
ID: 6886273
Actually - toArray() returns Object[], which you can't cast to String[]. You should use:

java.util.ArrayList al = new java.util.ArrayList();

al.add("hello");
al.add("world");

Object[] temp = al.toArray();
String myArray[] = new String[temp.length];
System.arraycopy(temp, 0, myArray, 0, temp.length);
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by:bobbit31
ID: 6886281
the mistakes one makes when they try to rush to be first to comment ;)
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Author Comment

by:Delphine_victorus
ID: 6886296
I tried......
it gives me an error.......
saying..incompatible types


found : java.lang.Object[]
required : java .lang.String[]
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Author Comment

by:Delphine_victorus
ID: 6886306
I tried......
it gives me an error.......
saying..incompatible types


found : java.lang.Object[]
required : java .lang.String[]
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LVL 92

Expert Comment

by:objects
ID: 6886983
Even easier:

java.util.ArrayList al = new java.util.ArrayList();

al.add("hello");
al.add("world");

String myArray[] = (String[]) al.toArray(new String[al.size()]);
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