Question

我是Java初学者，我从网上获取了一些代码并尝试了排列方案。我得到错误

Exception in thread "main"java.lang.ArrayIndexOutOfBoundsException: -1.

任何人都可以帮忙解决此问题。谢谢。

// Permute.java -- A class generating all permutations

  import java.lang.reflect.Array;
import java.util.Iterator;
import java.util.NoSuchElementException;

   public class Permute implements Iterator {

      private final int size;
     private final Object [] elements;  // copy of original 0 .. size-1
     private final Object ar;           // array for output,  0 .. size-1
     private final int [] permutation;  // perm of nums 1..size, perm[0]=0

     private boolean next = true;

     // int[], double[] array won't work :-(
     public Permute (Object [] e) {
        size = e.length;
        elements = new Object [size];    // not suitable for primitives
        System.arraycopy (e, 0, elements, 0, size);
        ar = Array.newInstance (e.getClass().getComponentType(), size);
        System.arraycopy (e, 0, ar, 0, size);
        permutation = new int [size+1];
        for (int i=0; i<size+1; i++) {
          permutation [i]=i;
        }
     }

    private void formNextPermutation () {
        for (int i=0; i<size; i++) {
           // i+1 because perm[0] always = 0
           // perm[]-1 because the numbers 1..size are being permuted
           Array.set (ar, i, elements[permutation[i+1]-1]);
        }
     }

     public boolean hasNext() {
        return next;
     }

     public void remove() throws UnsupportedOperationException {
        throw new UnsupportedOperationException();
     }

     private void swap (final int i, final int j) {
        final int x = permutation[i];
        permutation[i] = permutation [j];
        permutation[j] = x;
    }

     // does not throw NoSuchElement; it wraps around!
     public Object next() throws NoSuchElementException {

       formNextPermutation ();  // copy original elements

        int i = size-1;
        while (permutation[i]>permutation[i+1]) 
            i--;


        if (i==0) {
           next = false;
          for (int j=0; j<size+1; j++) {
              permutation [j]=j;
           }
          return ar;
       }

        int j = size;

      while (permutation[i]>permutation[j]) j--;
        swap (i,j);
        int r = size;
        int s = i+1;
        while (r>s) { swap(r,s); r--; s++; }

        return ar;
     }

     public String toString () {
        final int n = Array.getLength(ar);
        final StringBuffer sb = new StringBuffer ("[");
        for (int j=0; j<n; j++) {
           sb.append (Array.get(ar,j).toString());
           if (j<n-1) sb.append (",");
        }
        sb.append("]");
        return new String (sb);
     }

     public static void main (String [] args) {
        for (Iterator i = new Permute(args); i.hasNext(); ) {
           final String [] a = (String []) i.next();
           System.out.println (i);
        }
     }
  }

Answer 1

ArrayIndexOutOfBoundsException抛出表示已使用非法索引访问数组。索引为负数或大于或等于数组的大小因为你还没有发布任何堆栈跟踪。问题不清楚。但这些链接可能对您有所帮助。

如何在线程“main”java.lang.ArrayndexOutOfBoundsException中解决异常

1 个答案: