Java Generic syntax with Comparable interface

Question

I am trying to implement a simple insertion sort algorithm and make it generic to all the instance of Comparable interface.

public static <E extends Comparable<E>> void InsertionSort( E [] array)
{
    for(int i = 1; i < array.length; i++)
    {
        E current = array[i];

        int k;
        for(k = i-1; k >= 0 && current.compareTo(array[k]) < 0 ; k--)
        {
            array[k+1] = array[k];

        }

        array[k+1]=current;

    }

    for(int l = 0; l < array.length; l++)
    {
        System.out.print(array[l]+" ");

    }

    System.out.println();
}

The problem I have is I don't know the differences between

 <E extends Comparable<E>>

and

 <E extends Comparable>

They both work but I don't know the reason for the first one.

and the best option is <E extends Comparable<? super E>>

newacct
– newacct

2015-05-16 00:29:50 +00:00
Commented May 16, 2015 at 0:29 — newacct
– newacct, Commented May 16, 2015 at 0:29

Louis Wasserman · Accepted Answer · 2015-05-15 22:33:27Z

7

E extends Comparable<E> means that an instance of E can be compared to other objects of type E.

E extends Comparable means that an instance of E can be compared to...something. It's a raw type, which is bad. Don't do that.

answered May 15, 2015 at 22:33

Louis Wasserman

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