Randomising order of elements in vectors

Question

hi
i have a vector containing vectors containing Doubles (nightmare, i know!). Just wondering if there's an easy way of randomising the order or the elements in the main vector.
thanks,
al

Answer 1

This can be improved.
public class ARandouPermutation{
public static void main(String[] args) throws Exception{
java.util.Vector vec = new java.util.Vector();
for(int i=0;i<64;i++){// 64 is an example
    vec.add(new Double(i*1.0));
Object[] tmp0 = vec.toArray();
int originalSize = vec.size();// obtaining the original size of the Vector
vec.clear();  // setting to size zero
Object[] tmp1 = new Object[originalSize];
int[] indexarr = randPermute(originalSize);// this method is defined below
for(int j=0;j<indexarr.length;j++){
    tmp1[j] = tmp0[indexarr[j]];
tmp0=null;
arr=null;
for(int j=0;j<originalSize;j++){// this can be replaced by java.util.Arrays.asList(Object[])
  vec.add(tmp1[j]);
  System.out.println(((Double)vec.get(j)).toString());//test output
public static int[] randPermute(int L){// length L of the array returned is passed as an argument
   if(L<0) throw new IllegalArgumentException();
   int[] arr = new int[L];
   java.util.Random rand = new java.util.Random();
   for(int j=0;j<L;j++) arr[j]=j;
   int tmp, index=0;
Label:   while(index<L){
       tmp = rand.nextInt(L);
       for(int j=0;j<index;j++) {
            if(tmp==arr[j]) continue Label;
        arr[index]=tmp;
        index++;
   return arr;
}