Contents - Cultural View

Java syntax 187
Reference types
Reference types include class types, interface types, and array types. When the constructor is called an object is
created on the heap and a reference is assigned to the variable. When a variable of an object gets out of scope the
reference is broken and when there are no references left the object gets marked as garbage. The garbage collector
will then soon collect and destroy it.
A reference variable is null when it does not reference any object.
Arrays
Arrays in Java are created at runtime, just like class instances. Array length is defined at creation and cannot be
changed.
int[] numbers = new int[5];
numbers[0] = 2;
numbers[1] = 5;
int x = numbers[0];
Initializers
// Long syntax
int[] numbers = new int[5] {20, 1, 42, 15, 34};
// Short syntax
int[] numbers2 = {20, 1, 42, 15, 34};
Multi-dimensional arrays
In Java multi-dimensional arrays are represented as arrays of arrays. Technically they are represented by arrays of
references to another arrays.
int[][] numbers = new int[3][3];
number[1][2] = 2;
int[][] numbers2 = {{2, 3, 2}, {1, 2, 6}, {2, 4, 5}};
Due to the nature of the multi-dimensional arrays, sub-arrays may vary in length, so multi-dimensional arrays are not
bound to be rectangular unlike C:
int[][] numbers = new int[2][]; //Initialization of the first dimension
only
numbers[0] = new int[3];
numbers[1] = new int[2];