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。如果有人能指出一些技巧和建设性的意见,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吐出的内容。


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 <E>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<int>
  where E is a type-variable:
    E extends Comparable<E> declared in method <E>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 <E>printArray(E[])

最佳答案

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


您正在尝试调用签名为selectionSort()selectionSort(E[]),但是int不会扩展Comparable(它是primitive,甚至不是对象),因此类型不匹配。

您可以尝试创建一个Integer[]并将其传递。 Integer是一个对象,它扩展了Comparable<Integer>
另一种选择是重载selectionSort()以接受对象的通用类型并为每个所需的原语重载它。这是Java用于其Arrays.sort()方法的解决方案。

printArray()也是一样

09-10 06:40
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