Question

我有以下代码因为一般性问题而无法编译。它来自我尝试运行代码时。问题是我必须解决一般问题，但我无法发现它是否必须在StAlgo类或方法中改变某些东西。

public class StAlgo{

//signature selection sort
public <T extends Comparable<T>> int selectionSort(T[] array) {
}

 public static <T extends Comparable<T>> T[] getRandomPermutationOfIntegers(int size) {
      T[] data = (T[])new Comparable[size]; 
      for (Integer i = 0; i < size; i++) {
          data[i] = (T)i;
      }

      // shuffle the array
      for (int i = 0; i < size; i++) {
          T temp;
          int swap = i + (int) ((size - i) * Math.random());
          temp = data[i];
          data[i] = data[swap];
          data[swap] = temp;
      }
      return data;
  }

 public <T extends Comparable<T>> void trySelectionSort(){
      int N = 100, M = 100;  

      for(int i= 0; i < N; i++){
          T[] arrayInts = (T[])new Comparable[i];
          for(int j= 0; j < M; i++){
              arrayInts = getRandomPermutationOfIntegers(i);
              //Collections.shuffle(Arrays.asList(arrayInts));
              selectionSort(arrayInts);
          }
      }
  }
}







//Main class  has the folling code:

    StAlgosa s = new StAlgosa();
    s.trySelectionSort();

我收到以下错误：

Exception in thread "main" java.lang.Error: Unresolved compilation problem: 
    Bound mismatch: The generic method trySelectionSort() of type StAlgosa is not applicable for the arguments (). The inferred type Comparable<Comparable<T>> is not a valid substitute for the bounded parameter <T extends Comparable<T>>

我该如何解决？

感谢

Answer 1

部分修复方法是：

public class StAlgo<T extends Comparable<T>>

但是，您仍然会遇到问题

data[i] = (T) i;

因为您在该循环中创建了整数，但您的T类型可能无法隐式赋值...

Answer 2

这看起来像类型擦除问题 - http://download.oracle.com/javase/tutorial/java/generics/erasure.html

当你做T扩展Foo＆lt; T＆gt;，编译后，Java只记得T extends Foo。

结帐Generic Restriction Hell: Bound Mismatch帖子了解更多信息。

我如何解决这个通用错误

2 个答案: