What does <E> mean in the 1.5.0 API docs? 1

[markbanker]

I have noticed in the 1.5.0 API docs that <E> is used a great deal. Can someone tell me what it means?

Examples:
Interface Collection<E>
public interface Set<E> extends Collection<E>
add(E o)

Often times the 'E' is hyperlinked but when I click it it takes me to the Collections Interface.

I am unable to find any explanation for its usage.

Any feedback will be greatly appreciated.

Thanks,
Mark

 

[ishnid]

In Java 1.5, you can now specify what kind of Objects you want your Collections to hold. The <E> denotes this object type. It's best illustrated with an example:

Java 1.4.2:

ArrayList list = new ArrayList();
list.add( "add a string" );
String str = (String) list.get( 0 );

Notice that, since your ArrayList can only hold Objects, you have to cast the variable you retrieve from it as a String (in this case). With Java 1.5, we'll now specify that the contents of `list' are all Strings:

ArrayList<String> list = new ArrayList<String>();
list.add( "add a string" );
String str = list.get( 0 );

You can read more on Generics (as this is called) here

 

[markbanker]

Thanks ishnid!