How to make an array of arrays in Java

Question

Hypothetically  I have 5 string array objects   String   array1   new String    String   array2   new String    String   array3   new String    String   array4   new String    String   array5   new String      and I want another array object to contain those 5 string array objects  How do I do it  Can I put it in another array

User · Answer

While there are two excellent answers telling you how to do it, I feel that another answer is missing: In most cases you shouldn't do it at all.

Arrays are cumbersome, in most cases you are better off using the Collection API.

With Collections, you can add and remove elements and there are specialized Collections for different functionality (index-based lookup, sorting, uniqueness, FIFO-access, concurrency etc.).

While it's of course good and important to know about Arrays and their usage, in most cases using Collections makes APIs a lot more manageable (which is why new libraries like Google Guava hardly use Arrays at all).

So, for your scenario, I'd prefer a List of Lists, and I'd create it using Guava:

List<List<String>> listOfLists = Lists.newArrayList();
listOfLists.add(Lists.newArrayList("abc","def","ghi"));
listOfLists.add(Lists.newArrayList("jkl","mno","pqr"));

User · Answer

try  String     arrays   new String 5

User · Answer

Like this   String     arrays     array1  array2  array3  array4  array5      or  String     arrays   new String       array1  array2  array3  array4  array5       The latter syntax can be used in assignments other than at the point of the variable declaration  whereas the shorter syntax only works with declarations

User · Answer

there is the class I mentioned in the comment we had with Sean Patrick Floyd   I did it with a peculiar use which needs WeakReference  but you can change it by any object with ease   Hoping this can help someone someday     import java lang ref WeakReference  import java util LinkedList  import java util NoSuchElementException  import java util Queue               author leBenj     public class Array2DWeakRefsBuffered lt T gt        private final WeakReference lt T gt       array      private final Queue lt T gt   buffer       private final int  width       private final int  height       private final int  bufferSize        SuppressWarnings   unchecked        public Array2DWeakRefsBuffered  int w   int h   int bufferSize                  width   w           height   h           bufferSize   bufferSize           array   new WeakReference  width   height            buffer   new LinkedList lt T gt                           Tests the existence of the encapsulated object            This DOES NOT ensure that the object will be available on next call           param x         param y         return         throws IndexOutOfBoundsException        public boolean exists  int x   int y   throws IndexOutOfBoundsException               if  x  gt    width    x  lt  0                         throw new IndexOutOfBoundsException   Index out of bounds  get      x       x                            if  y  gt    height    y  lt  0                         throw new IndexOutOfBoundsException   Index out of bounds  get      y       y                            if   array x  y     null                         T elem    array x  y  get                if  elem    null                             return true                                  return false                        Gets the encapsulated object         param x         param y         return         throws IndexOutOfBoundsException         throws NoSuchElementException             public T get  int x   int y   throws IndexOutOfBoundsException   NoSuchElementException               T retour   null          if  x  gt    width    x  lt  0                         throw new IndexOutOfBoundsException   Index out of bounds  get      x       x                            if  y  gt    height    y  lt  0                         throw new IndexOutOfBoundsException   Index out of bounds  get      y       y                            if   array x  y     null                         retour    array x  y  get                if  retour    null                             throw new NoSuchElementException   Dereferenced WeakReference element at       x           y                                          else                       throw new NoSuchElementException   No WeakReference element at       x           y                            return retour                        Add replace an object         param o         param x         param y         throws IndexOutOfBoundsException             public void set  T o   int x   int y   throws IndexOutOfBoundsException               if  x  gt    width    x  lt  0                         throw new IndexOutOfBoundsException   Index out of bounds  set      x       x                            if  y  gt    height    y  lt  0                         throw new IndexOutOfBoundsException   Index out of bounds  set      y       y                             array x  y    new WeakReference lt T gt   o                store local  visible  references   avoids deletion  works in FIFO mode          buffer add  o            if  buffer size    gt   bufferSize                         buffer poll                         Example of how to use it       a 5x5 array  with at most 10 elements  bufferized  - gt  the last 10 elements will not be taken by GC process Array2DWeakRefsBuffered lt Image gt  myArray   new Array2DWeakRefsBuffered lt Image gt  5 5 10   Image img   myArray set anImage 0 0   if myArray exists 3 3         System out println  Image at 3 3 is still in memory

[java] How to make an array of arrays in Java

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