I know that the array declaration below is correct:
String[][] arrayNew={{"teresa","human","jennifer"},{"18","20"},{"nothing"}};
I understand that String and array are two different object types in java.So how come the string array arrayNew is successfully storing three different arrays in it.
An int array can not store doublesbut how come a string array is able to store arrays?
You can think of Type[] as one-dimensional array which can store elements of described Type. So Type[] array can look like {Type0, Type1, Type2}.
Now lets say that we want to create array which can store 1D arrays. How should we declare it? Our Type will need to be replaced with String[] which will give us
String[][] arrayNew
^^^^^^^^
type of elements which can be stored directly in `arrayNew`
So since Type is String[], it means that arrayNew is not String array, but array of String arrays
{ [0] [1] [2] }
↓ ↓ ↓
String[], String[], String[]
//each of these 1D array can store its own elements.
arrayNew can store only 1D String arrays, and these 1D arrays can store Strings.You are just creating a 2D array (An array of String array).
On this particular case, you created a jagged array.
You could do the same for int array as well:
int[][] array = {{1,2,3}, {4,5}, {6}};
Multidimensional arrays are array of arrays:
String[] arrayA; //Array of Strings
String[][] arrayB; //Array of (Array of Strings)
String[][][] arrayC; //Array of (Array of (Array of Strings))
String[][][][] arrayD; //Array of (Array of (Array of (Array of Strings)))
arrayNew is not a string array (String[]) it's an array of arrays of strings (String[][]). As such, each of its elements is an array of strings - {"teresa","human","jennifer"} (an array of strings with three elements) , {"18","20"} (an array of strings with two elements) and {"nothing"} (an array of strings with a single element).
Since it's declared as String[][] with two [] this means it's a two-dimensional array.
In other words:
String - can contain only one string
String[] - can contain an array of strings (multiple strings)
String[][] - can contain an array of arrays of strings (multiple arrays of multiple strings)
... and so on
In this case the string array can hold multiple arrays since its a Two Dimensional Array. Here is a documentation about it.
Integers can also do that as the following:
int[][] myArray = { {0, 1, 2, 3},
{3, 2, 1, 0},
{3, 5, 6, 1},
{3, 8, 3, 4} };
String[] is an array of Strings.
Foo[] is an array of Foos.
Bar[] is an array of Bars.
So, String[][] is an array of String[]s. I.e. an array of arrays of Strings. That's why it can store arrays of Strings.
arrayNew is a reference to an 2d array of type String and all the elements are also of string type, so it compiles.
ex: String[] arr = {"abc","xyz"};, arr is referring to an array of type String ,arr is not the array itself.
