How to convert object array to string array in Java

Question

Another alternative to System.arraycopy:

String[] stringArray = Arrays.copyOf(objectArray, objectArray.length, String[].class);

In Java 8:

String[] strings = Arrays.stream(objects).toArray(String[]::new);

To convert an array of other types:

String[] strings = Arrays.stream(obj).map(Object::toString).
                   toArray(String[]::new);

System.arraycopy is probably the most efficient way, but for aesthetics, I'd prefer:

 Arrays.asList(Object_Array).toArray(new String[Object_Array.length]);

I see that some solutions have been provided but not any causes so I will explain this in detail as I believe it is as important to know what were you doing wrong that just to get "something" that works from the given replies.

First, let's see what Oracle has to say

 * <p>The returned array will be "safe" in that no references to it are
 * maintained by this list.  (In other words, this method must
 * allocate a new array even if this list is backed by an array).
 * The caller is thus free to modify the returned array.

It may not look important but as you'll see it is... So what does the following line fail? All object in the list are String but it does not convert them, why?

List<String> tList = new ArrayList<String>();
tList.add("4");
tList.add("5");
String tArray[] = (String[]) tList.toArray();   

Probably, many of you would think that this code is doing the same, but it does not.

Object tSObjectArray[] = new String[2];
String tStringArray[] = (String[]) tSObjectArray;

When in reality the written code is doing something like this. The javadoc is saying it! It will instatiate a new array, what it will be of Objects!!!

Object tSObjectArray[] = new Object[2];
String tStringArray[] = (String[]) tSObjectArray;   

So tList.toArray is instantiating a Objects and not Strings...

Therefore, the natural solution that has not been mentioning in this thread, but it is what Oracle recommends is the following

String tArray[] = tList.toArray(new String[0]);

Hope it is clear enough.

The google collections framework offers quote a good transform method,so you can transform your Objects into Strings. The only downside is that it has to be from Iterable to Iterable but this is the way I would do it:

Iterable<Object> objects = ....... //Your chosen iterable here
Iterable<String> strings = com.google.common.collect.Iterables.transform(objects, new Function<Object, String>(){
        String apply(Object from){
             return from.toString();
        }
 });

This take you away from using arrays,but I think this would be my prefered way.

This one is nice, but doesn't work as mmyers noticed, because of the square brackets:

Arrays.toString(objectArray).split(",")

This one is ugly but works:

Arrays.toString(objectArray).replaceFirst("^\\[", "").replaceFirst("\\]$", "").split(",")

If you use this code you must be sure that the strings returned by your objects' toString() don't contain commas.