converting Arrays to List?

[Avander Be]

Following code is based on code from K&B SCJP Study Guide p. 559.

import java.util.*;
 
public class ArrayToList {
public static void main( String[] args) {
String[] sa = { "one", "two", "three", "four", "five"};

List<String> sList = Arrays.asList( sa); // make List from array

System.out.println("List size : "+ sList.size());
System.out.println("List elem2: "+ sList.get(2));

sList.set( 3, "set"); // change list
sa[1] = "match"; // change array

for ( String s : sa) { // dump array
System.out.println(s+ " ");
}
for ( String s : sList) { // dump list
System.out.println(s+ " ");
}
}
}    

I had to add the import and the <String> to List in order to compile.

What puzsles me is where did that List type come from?? The only List type I found in the Java doc is an... interface!

[Freddy Wong]

The List can be found in java.util.List. You have import java.util.*, that's why you can use the List.

[Shilpa]

Arrays.asList(..) has changed from
public static List asList(Object a)
to (Java 1.5)
public static <T> List<T> asList(T... a)

Shilpa

[Rob Spoor]

Originally posted by Avander Be:

What puzsles me is where did that List type come from?? The only List type I found in the Java doc is an... interface!

You must have overlooked java.awt.List, but that's a GUI element

It's right that java.util.List is an interface. The Arrays class has an internal class that implements List and wraps arrays. An instance of this class is instantiated when you call Arrays.asList. You don't need to know the full name of the class, only that it implements List, and you cannot add or remove elements. All other List methods can be called without a problem.

[Avander Be]

Originally posted by Rob Prime:

You must have overlooked java.awt.List, but that's a GUI element

Yep, I did see it but figured out it was kinda 'out of scope' here :-)).

Originally posted by Rob Prime:
It's right that java.util.List is an interface. The Arrays class has an internal class that implements List and wraps arrays. An instance of this class is instantiated when you call Arrays.asList. You don't need to know the full name of the class, only that it implements List, and you cannot add or remove elements. All other List methods can be called without a problem.

It's just another 'polymorphism' trick isn't it?

[Rob Spoor]

You got it.