Unchecked call to compareTo

Posted by Dave Jarvis on Stack Overflow See other posts from Stack Overflow or by Dave Jarvis
Published on 2011-01-02T05:31:03Z Indexed on 2011/01/02 5:54 UTC
Read the original article Hit count: 272

Filed under:

java

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generics

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collections

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comparator

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comparable

Background

Create a Map that can be sorted by value.

Problem

The code executes as expected, but does not compile cleanly:

http://pastebin.com/bWhbHQmT

The syntax for passing Comparable as a generic parameter along to the Map.Entry<K, V> (where V must be Comparable?) -- so that the (Comparable) typecast shown in the warning can be dropped -- eludes me.

Warning

Compiler's cantankerous complaint:

SortableValueMap.java:24: warning: [unchecked] unchecked call to compareTo(T) as a member of the raw type java.lang.Comparable
   return ((Comparable)entry1.getValue()).compareTo( entry2.getValue() );

Question

How can the code be changed to compile without any warnings (without suppressing them while compiling with -Xlint:unchecked)?

Related

Thank you!

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