An Experienced Programmer’s Introduction to Java - Java Application Development on Linux - page 73

This is the new syntax that tells the compiler that we are putting String s into
the List . The compiler will enforce that and give a compile time error if we
try to add any other type to the List .
Now we come to the for loop. Read it as “for str in loa ” or “for String
values of str iterating over loa .” We will get an iterator working out of sight
that will iterate over the values of loa , our List . The values (the result of the
next() method) will be put in the String variable str . So we can use str
inside the body of the loop, with it taking on successive values from the
collection.
Let's describe the syntax, then, as
for ( SomeType variable : SomeCollectionVariable ) {
}
which will define variable to be of type SomeType and then iterate over the
SomeCollectionVariable . Each iteration will execute the body of the loop,
with the variable set to the next() value from the iterator. If the collection is
empty, the body of the loop will not be executed.
This variation of the for loop works for arrays as well as for these new
typed collections. The syntax for arrays is the same. Example 3.16 will echo the
arguments on the command line, but without loading up a List like we did
in our previous example.
Example 3.16 A for loop iterator for arrays
import java.util.*;
public class
Forn
{
public static void
main(String [] args)
{
for(String str : args) {
System.out.println("arg="+str);
}
} // main
} // Forn