An array is a linear data structure in Java.
Arrays may hold primitive data types, object references, as well as other arrays.
Array elements must have a uniform type in all its elements.
When created, an array has a size that is predetermined and may not be extended dynamically.
An array variable is declared by specifying the type of array elements followed by a pair of square brackets ([]).
An array is created using the new keyword followed by the type and a size in square brackets ([…]).
To access an element of an array, follow the array variable with a pair of square brackets containing the index of the array element. This form of element access may be used for both reading and assigning values to an array element.
Array elements begin at index 0 and end at an index of one less than the length of the array.
The length of an array may be determined using the .length property of the array.
An array may be initialized at the time it is created by leaving out the size of the array but following with curly braces containing a comma-delimited list of initializer values.
A shorthand for initializing an array is to declare an array variable with empty square brackets and assign it directly to a curly brace-delimited list of values.
Accessing all elements of an array may be performed with a while- or for-loop which generates all indexes, typically as a loop counter.
An array element may itself be an array.
An array of arrays is referred to as a "multidimensional" array.
2D array variables may be declared with a type followed by two pairs of square brackets.
2D arrays may be created using the new keyword following by two pairs of square brackets containing the number of elements in each dimension. In this case the array is rectangular in shape.
To access an element in a 2D array use the array variable followed by two pairs of square brackets, each containing indexes.
A 2D array may be initialized by leaving out dimensions when creating the array and followed by nested curly braces containing comma-separated values.
The second dimension of a 2D array is made up of arrays that are not required to have uniform length. This is referred to as a ragged array.
2D ragged arrays may be created by leaving out the length of the second dimension. In this case each array element starts with the default value null.
When using a ragged array, each element of the first dimension may be assigned to a 1D array of non-uniform length, provided the array type is compatible.
A shorthand for initializing a ragged 2D array is to declare an array variable and assign it directly to nested curly brace-delimited lists of values, where the length of each subordinate list may vary.
To print the elements of a ragged array with iteration, the inner loop extent must use each subordinate array length to test the loop counter value.
Arrays of dimension higher than two are possible by following the pattern for extending from 1D to 2D arrays.
Use the java.util.Arrays package to access static utility functions for manipulating arrays.
Arrays are passed to methods by reference, just like any other object.
The public static void main()String[] args) method takes an array of Strings parameter, where the array’s Strings are read from the user input following the java command and class name. This array is referred to as the programs command line arguments.
