Collections.copy Error: Source does not fit in dest

Today in the use of collections. Copy method time, error

Source does not fit in dest

The code in your own method is as follows:

list<option> prostatelist = Selectoptionsutil.getoptionsbyid ("prostate");        list<option> resultlist = new arraylist<option> (20);//Generate a newer list to prevent the update operation from affecting the cache variable        collections.copy ( Resultlist, prostatelist);//list copy

First go to see the source of Collections.copy:

  int srcsize = Src.size ();  if (Srcsize > Dest.size ())            throw new Indexoutofboundsexception ("Source does not fit in dest");

Found to be comparison size.

And, to view the source code of ArrayList, found that the use did not change size.

Public ArrayList (int initialcapacity) {        super ();        if (initialcapacity < 0)            throw new IllegalArgumentException ("Illegal capacity:" +                                               initialcapacity);        This.elementdata = new object[initialcapacity];    }

In a moment I was spartan.

Borrow the almighty Google search, found: http://stackoverflow.com/questions/6147650/java-lang-indexoutofboundsexception-source-does-not-fit-in-dest

The great God has encountered this problem.

See for yourself and find that you can do this directly using the following code.

    list<option> prostatelist = Selectoptionsutil.getoptionsbyid ("prostate");        list<option> resultlist = new arraylist<option> (prostatelist);//Generate a newer list to prevent the update operation from affecting the cache variable

You can use the construction method directly, without using the Copy method.

    /**     * Constructs a list containing     the elements of the specified * collection, in the order they is returned by T He collection ' s     * iterator.     *     * @param c the collection whose elements is to being placed into this list     * @throws NullPointerException if the s Pecified collection is null     *    /public ArrayList (collection<? extends e> c) {        elementdata = C.toarray () ;        size = Elementdata.length;        C.toarray might (incorrectly) not return object[] (see 6260652)        if (Elementdata.getclass ()! = Object[].class) 
   elementdata = arrays.copyof (elementdata, size, object[].class);    }

Collections.copy Error: Source does not fit in dest