选择排序与泛型

Question

我使用整数对选择进行排序，并且可以正常工作，当我尝试修改程序以使用泛型时，编译器会抱怨并且我不知道如何解决它。如果有人能提出一些建议和建设性的意见，我将不胜感激。这是代码。

public class SelelctionSort 
{
    public static void main(String[] args) 
    {
        int[] list = {34, 17, 23, 35, 45, 9, 1};
        System.out.println("Original Array: ");
        printArray(list);

        selectionSort(list);
        System.out.println("\nSelection sort:");
        printArray(list);

    }

    //selection sort
    public static <E extends Comparable<E>> void selectionSort(E[] list)
    {
        for(int i=0; i<list.length -1; i++)
        {
            int iSmallest = i;

            for(int j=i+1; j<list.length; j++)
            {
                if(list[iSmallest].compareTo((list[j])) > 0  )
                {
                    iSmallest = j;
                }
            }
            E iSwap = list[iSmallest];
            list[iSmallest] = list[i];
            list[i] = iSwap;

        }
    }

    public static <E> void printArray(E[] list)
    {

        for(int i=0; i<list.length; i++)
        {
            System.out.print(list[i] + ", ");
        }
    }
}

以下是javac吐出来的东西。

SelelctionSort.java:7: error: method printArray in class SelelctionSort

cannot be applied to given types;
printArray(list);
^
required: E[]
found: int[]
reason: inferred type does not conform to declared bound(s)
inferred: int
bound(s): Object
where E is a type-variable:
E extends Object declared in method printArray(E[])
SelelctionSort.java:9: error: method selectionSort in class
SelelctionSort cannot be applied to given types;
selectionSort(list);
^
required: E[]
found: int[]
reason: inferred type does not conform to declared bound(s)
inferred: int
bound(s): Comparable
where E is a type-variable:
E extends Comparable declared in method selectionSort(E[])
SelelctionSort.java:11: error: method printArray in class SelelctionSort
cannot be applied to given types;
printArray(list);
^
required: E[]
found: int[]
reason: inferred type does not conform to declared bound(s)
inferred: int
bound(s): Object
where E is a type-variable:
E extends Object declared in method printArray(E[])

Answer 1

int[] list = {34, 17, 23, 35, 45, 9, 1};
...
selectionSort(list);

您正在尝试调用selectionSort()哪个签名是selectionSort(E[])，但是int不扩展Comparable（它是原始的，甚至不是对象）-因此类型不匹配。

您可以尝试创建Integer[]并传递它。Integer是一个对象并且它扩展Comparable<Integer>。
另一种方法是 重载
selectionSort()以接受对象的通用类型，并为每个所需的基元重载它。这是java用于其Arrays.sort()方法的解决方案。

同样适用于 printArray()