How to convert object array to string array in Java

Question

I use the following code to convert an Object array to a String array    Object Object Array   new Object 100          get values in the Object Array  String String Array   new String Object Array length    for  int i 0 i lt String Array length i    String Array i  Object Array i  toString      But I wonder if there is another way to do this  something like    String Array  String   Object Array    But this would cause a runtime error  Exception in thread  AWT-EventQueue-0  java lang ClassCastException   Ljava lang Object  cannot be cast to  Ljava lang String   What s the correct way to do it

User · Answer

System arraycopy is probably the most efficient way  but for aesthetics  I d prefer    Arrays asList Object Array  toArray new String Object Array length

User · Answer

For your idea  actually you are approaching the success  but if you do like this should be fine   for  int i 0 i lt String Array length i    String Array i   String Object Array i     BTW  using the Arrays utility method is quite good and make the code elegant

User · Answer

If you want to get a String representation of the objects in your array  then yes  there is no other way to do it   If you know your Object array contains Strings only  you may also do  instread of calling toString       for  int i 0 i lt String Array length i    String Array i    String  Object Array i     The only case when you could use the cast to String   of the Object Array would be if the array it references would actually be defined as String     e g  this would work       Object   o   new String 10       String   s    String    o

User · Answer

Object arr3   list1 toArray       String common   new String arr3 length       for  int i 0 i lt arr3 length i             common i   String arr3 i

User · Answer

Easily change without any headche  Convert any object array to string array         Object drivex      1 2        for int i 0  i lt drive length   i                          Str i   drivex i  toString                System out println Str i

User · Answer

You can use type-converter   To convert an array of any types to array of strings you can register your own converter    TypeConverter registerConverter Object   class  String   class  new Converter lt Object    String   gt                Override         public String   convert Object   source                String   strings   new String source length               for int i   0  i  lt  source length   i                      strings i    source i  toString                              return strings                      and use it     Object   objects   new Object    1  23 43  true   text    c       String   strings   TypeConverter convert objects  String   class

User · Answer

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 lt Object gt  objects             Your chosen iterable here Iterable lt String gt  strings   com google common collect Iterables transform objects  new Function lt Object  String gt             String apply Object from                return from toString                     This take you away from using arrays but I think this would be my prefered way

User · Answer

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

User · Answer

Another alternative to System arraycopy   String   stringArray   Arrays copyOf objectArray  objectArray length  String   class

User · Answer

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      lt p gt 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 lt String gt  tList   new ArrayList lt String gt     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

User · Answer

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

[java] How to convert object array to string array in Java

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