Keith Devens .com - Weblog: Java's (typed/generic) collections suck (update: no they don't)

Sunday, July 24, 2005

Java's (typed/generic) collections suck (update: no they don't)

Java's typed/generic collections ~~suck~~ are ok, see below:

import java.util.ArrayList;

import java.util.HashMap;

import java.util.List;

import java.util.Map;



public class TokenTest {

    public static void main(String[] args) {

        Map<String, List<String[]>> tokenMap = new HashMap<String, List<String[]>>();

        List tokenList = tokenMap.get("foo");

        for (String[] tokenTerms : tokenList){

            System.out.println(tokenTerms);

        }

    }

}

Then:

$>javac TokenTest.java

TokenTest.java:10: incompatible types

found   : java.lang.Object

required: java.lang.String[]

        for (String[] tokenTerms : tokenList){

                                   ^

1 error

Am I doing something wrong or is Java's typing stupid? Also note that Java didn't understand that ArrayList is a subtype of List when I tried to create a new HashMap<String, ArrayList<String[]>>();.

Update: Jürgen pointed out in a comment that List tokenList should have been List<String[]> tokenList. Problem solved. Thanks!