Selecting one dimension of a two dimension array?

Question

hi, i want to select only one dimension of an array and put it into an arraylist (or casting the array verbatim into the arraylist)
for example, here is an two dimension array:
Object[][] data =
     {  { new Date(), "A", new Integer(1), Boolean.TRUE },
     { new Date(), "B", new Integer(2), Boolean.FALSE },
     { new Date(), "C", new Integer(9), Boolean.TRUE },
     { new Date(), "D", new Integer(4), Boolean.FALSE}
     };and i want to cast it into an arraylist, what i have in mind (a bit troublesome is the following:)
ArrayList dataArray = new ArrayList();
dataArray.add(data[0]);
dataArray.add(data[1]);
dataArray.add(data[2]);
dataArray.add(data[3]);
System.out.println(dataArray);when come upon the last System.out.println, i got some seemly useless addresses:
[[Ljava.lang.Object;@f73c1, [Ljava.lang.Object;@789144, [Ljava.lang.Object;@1893efe, [Ljava.lang.Object;@186c6b2]
how do you accomplish casting a two dimension array into an arraylist, but the second dimension of the arraylist is kept as Array of Objects? thanks alot!

Answer 1

First, the strings that are printed out are the value of the hashcode for the specific object. That is the default value that is printed out for any object reference in a class that inherits the toString() method from the Object class. This is true for arrays. Your ArrayList contains array references in it..
So, you are printing the object hashcodes for the arrays in your ArrayList, instead of the contents of those arrays. It would be better if you created ArrayLists, or even designed an object that stores your data, and stored those inside your ArrayList. ArrayList has an overwritten toString() method that will print the contents instead of the object hashcode, so an ArrayList containing ArrayLists would print your data the way you want. If you define your own class, you will need to provide a toString() method that prints the contents the way you want.
PS, look at http://java.sun.com/j2se/1.5.0/docs/api/java/util/AbstractCollection.html#toString() for more information on the toString() method used by ArrayList.
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