一个用于产生全排列的java类代码，排列java类代码,// Permute.j

一个用于产生全排列的java类代码，排列java类代码,// Permute.j

// Permute.java -- A class generating all permutationsimport java.util.Iterator;import java.util.NoSuchElementException;import java.lang.reflect.Array;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);   }  //code from http://www.byrx.net/codes/   public static void main (String [] args) {      for (Iterator i = new Permute(args); i.hasNext(); ) {         final String [] a = (String []) i.next();         System.out.println (i);      }   }}