Question

Here is a very simple example in Java intended to print out all of the system environment variables:

http://www.devdaily.com/blog/post/java/java-how-to-print-system-env-environment-variables

The code seems pretty simple – it just iterates over the environment variables as a mapping, printing each key and value, however when I execute the code I get the following error:

Exception in thread "main" java.lang.Error: Unresolved compilation problem: 
Type mismatch: cannot convert from element type Object to String

What is going on here? Is the example garbage or have I set up my Eclipse / JDK in a manner which prevents this from working?

FYI, I’m using Windows XP with JDK 1.6.0_24 x86 on an update version of Eclipse.

Answer 1

The example code is simply wrong – it does not (and never could) compile and eclipse should show that in the code.

The problem is that Map envMap is a raw type, so envMap.keySet() is also a raw type and its elements cannot be implicitly converted to String in the enhanced for loop.

The solution: simply change the Map definition to:

Map<String,String> envMap = System.getenv();