"Some input files use unchecked or unsafe operations."

When i compile my (1.4.2_05) Java project I get the following

[javac] Note: Some input files use unchecked or unsafe operations.

[javac] Note: Recompile with -Xlint:unchecked for details.

Is there any doc explaning this? At http://java.sun.com/j2se/1.5.0/docs/relnotes/features.html#javac I found a note about this "-Xlint" option, but I want to know _what_ code is producing this "unchekced/unsafe" operations.

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