type parameter X is not within its bound

[Mark]

I get the following error, and I'm not sure why.

EKT.java:7: type parameter WordPair is not within its bound
static BST<WordPair> tree = new BST<WordPair>();
^
EKT.java:7: type parameter WordPair is not within its bound
static BST<WordPair> tree = new BST<WordPair>();
^
2 errors

Terminated with exit code 1.

BST is declared as: class BST<T extends Comparable<? super T>>
and WordPair is declared as: class WordPair implements Comparable

Let me know if you need more information.

WordPair implements Comparable, and BST requires a Comparable class.
I'm not sure what the problem is. BST<Integer> works fine.

 

[Mark]

I get the following error, and I'm not sure why.

EKT.java:7: type parameter WordPair is not within its bound
static BST<WordPair> tree = new BST<WordPair>();
^
EKT.java:7: type parameter WordPair is not within its bound
static BST<WordPair> tree = new BST<WordPair>();
^
2 errors

BST is declared as: class BST<T extends Comparable<? super T>>
and WordPair is declared as: class WordPair implements Comparable

Let me know if you need more information.

WordPair implements Comparable, and BST requires a Comparable class.
I'm not sure what the problem is. BST<Integer> works fine.

I forget how I came up with this solution... it hurt my head just
thinking about it... but here's what I came up with (it compiles now)

Just had to change WordPair's declaration to: class WordPair implements
Comparable<WordPair>
and then change my compareTo function to
public int compareTo(WordPair wp)
instead of taking an object... which also means that I no longer have
to cast it to a wordpair! Two birds with one stone.

 

[hiwa]

I get the following error, and I'm not sure why.

EKT.java:7: type parameter WordPair is not within its bound
static BST<WordPair> tree = new BST<WordPair>();
^
EKT.java:7: type parameter WordPair is not within its bound
static BST<WordPair> tree = new BST<WordPair>();
^
2 errors

BST is declared as: class BST<T extends Comparable<? super T>>
and WordPair is declared as: class WordPair implements Comparable

Let me know if you need more information.

WordPair implements Comparable, and BST requires a Comparable class.
I'm not sure what the problem is. BST<Integer> works fine.

WordPair implements Comparable<WHAT??>

 

[Hendrik Maryns]

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Mark schreef:

I forget how I came up with this solution... it hurt my head just
thinking about it... but here's what I came up with (it compiles now)

Just had to change WordPair's declaration to: class WordPair implements
Comparable<WordPair>
and then change my compareTo function to
public int compareTo(WordPair wp)
instead of taking an object... which also means that I no longer have
to cast it to a wordpair! Two birds with one stone.

Indeed, as I mentioned in my other post, Comparable is parameterised.
Once you start off with generics, you have to use parameters on /all/
generic classes.

H.
- --
Hendrik Maryns
http://tcl.sfs.uni-tuebingen.de/~hendrik/
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