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Compiler warnings

 
Greenhorn
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I hope this topic is all right for this forum. It seems like something a beginner would see frequently.

I am working through Head First Java, and often get compiler warnings like those below when compiling the code listings downloaded from the book's web site. What are they saying? Better yet where can I find a list of warnings with understandable explanations?

C:\Documents and Settings\forest gump\My Documents\My Books
\HeadFirstJava\chapter-6\jwj\GameHelper.java:82:
warning: [unchecked] unchecked call to add(E) as a member of the raw type java.util.ArrayList
alphaCells.add(temp.concat(Integer.toString(row)));
^
C:\Documents and Settings\forest gump\My Documents\My Books
\HeadFirstJava\chapter-6\jwj\GameHelper.java:90:
warning: [unchecked] unchecked conversion
found : java.util.ArrayList
required: java.util.ArrayList<java.lang.String>
return alphaCells;
^
2 warnings

Tool completed successfully

I usually type in the code from the book, so I can get familiar with the syntax. A compile with only warnings is a delight to see.
 
Ranch Hand
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I believe what you are seeing is something specific to JSDK 1.5

In 1.5 you can use generics and specify what types should be in a Collection.
 
Sheriff
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try adding the:
-source 1.4
switch when compiling and see if it goes away.
 
Ranch Hand
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Warnings let you know of potential problems, but they don't prevent the code from compiling.
 
James Jennings
Greenhorn
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The warning was pointing to this expression:

ArrayList alphaCells = new ArrayList();

After doing some research, I changed it to:

ArrayList<String> alphaCells = new ArrayList<String>();

and the warnings go away. Apparently the code has not been updated from the 1st edition, which I assume was published before java 1.5 was released. Probably because some (many?) people have not updated from java 1.4.

P.S. I'm a (obsessive) perfectionist, Jeff.
P.P.S. Thanks for the speedy responses, everyone.
 
James Jennings
Greenhorn
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I just noticed that Head First Java, 2nd Edition book does have the java 1.5 code with the <String>, it is only the download files that not updated.
 
With a little knowledge, a cast iron skillet is non-stick and lasts a lifetime.
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