The java::listify Command

Usage:

java::listify ?-noconvert|class? collectionORenumeration

The java::listify command trasforms a java collection or a java enumeration in a tcl-list.

The collectionORenumertion object is a handle to a Java object that implements the java.util.Collection interface or the java.util.Enumeration interface, or an handle to null

If CollectionOrenumeration is an handle to null, java::listify returns an empty list.

The java::listify command is similar to the getrange method working on a java-array, except that elements can be of different classes.

In its simpler form (without -noconvert> or class),java::listify tries to convert the enum/collections's elements in simple tcl-types (i.e. strings !).
This implicit conversions works only on basic elements (i.e. Integer, Double, .., String); otherwise the element is extracted as a java-object.
Note that null elements are converted to the empty string.

If -noconvert option is used, then all collection's elements are returned as java.objects.
If class is specified, then all collection's elements are returned as casted java.objects. An error is raised if class is incompatible with any element.

Examples:

Collection Example:

Assume for a moment that the user has defined a Java class. This class contains a static method that returns a collection object. The JDK 1.5 code to iterate over this collection would be:

Collection<String> c = MyJavaClass.getCollection();

for (String elem : c) {
    System.out.println("elem is " + elem);
}

This same iteration could be implemented in Tcl, using the java::listify command.

set c [java::call MyJavaClass getCollection]

foreach elem [java::listify {String} $c] {
    puts "elem is $elem"
}

Elements in a Hashtable:

The java::listify command can be used to iterate over elements in a Hashtable or any other Map implementation.

java::import -package java.util Hashtable Map
set t [java::new Hashtable]
$t put "One" "onestr"
$t put "Two" "twostr"

foreach e [java::listify {java.util.Map.Entry} [$t entrySet]] {
    set key [[$e getKey] toString]
    set value [[$e getValue] toString]
    puts "$key -> $value"
}

The code above will print the following to the console:

One -> onestr
Two -> twostr

Automatic Type Conversion:

The java::listify command supports automatic conversion of a Java primitive wrapper in a collection to a Tcl value. For example, given a Vector of java.lang.Integer, its elements are automatically converted in Tcl-integers.

set v [java::new java.util.Vector]
$v addElement [java::new Integer 0]
$v addElement [java::new Integer 1]
$v addElement [java::new Integer 2]

puts "vector elements are: [java::listify $v]"

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