Arrays Background Programmer often need the ability to represent a group of values as a list List may be one dimensional or multidimensional Java provides arrays and the collection classes Consider arrays first Basic terminology List is composed of elements Elements in a list have a common name The list as a whole is referenced through the common name List elements are of the same type the base type Elements of a list are referenced by subscripting indexing the common name Java array features Subscripts are denoted as expressions within brackets Base element type can be any type Size of array can be specified at run time Index type is integer and the index range must be 0 n 1 Where n is the number of elements Automatic bounds checking Ensures any reference to an array element is valid Data field length specifies the number of elements in the list Array is an object Has features common to all other objects Array variable definition styles Without initialization ElementType id Type of values in list Brackets indicate array variable being defined Name of list Array variable definition styles With initialization Nonnegative integer expression specifying the number of elements in the array ElementType id new ElementType n Reference to a newarray of n elements Example Definitions char c int value new int 10 Causes Array object variable c is un initialized Array object variable v references a new ten element list of integers Each of the integers is default initialized to 0 c value 0 0 0 0 0 0 Consider int v new int 10 int i 7 int j 2 int k 4 v 0 1 v i 5 v j v i 3 v j 1 v i v 0 v v j 12 System out println v 2 v k Integer parseInt stdin readLine v 0 0 0 0 0 0 0 0 0 0 v 0 v 1 v 2 v 3 v 4 v 5 v 6 v 7 v 8 v 9 Consider int v new int 10 int i 7 int j 2 int k 4 v 0 1 v i 5 v j v i 3 v j 1 v i v 0 v v j 12 System out println v 2 v k Integer parseInt stdin readLine v 1 0 0 0 0 0 0 0 0 0 v 0 v 1 v 2 v 3 v 4 v 5 v 6 v 7 v 8 v 9 Consider int v new int 10 int i 7 int j 2 int k 4 v 0 1 v i 5 v j v i 3 v j 1 v i v 0 v v j 12 System out println v 2 v k Integer parseInt stdin readLine v 1 0 0 0 0 0 0 5 0 0 v 0 v 1 v 2 v 3 v 4 v 5 v 6 v 7 v 8 v 9 Consider int v new int 10 int i 7 int j 2 int k 4 v 0 1 v i 5 v j v i 3 v j 1 v i v 0 v v j 12 System out println v 2 v k Integer parseInt stdin readLine v 1 0 8 0 0 0 0 5 0 0 v 0 v 1 v 2 v 3 v 4 v 5 v 6 v 7 v 8 v 9 Consider int v new int 10 int i 7 int j 2 int k 4 v 0 1 v i 5 v j v i 3 v j 1 v i v 0 v v j 12 System out println v 2 v k Integer parseInt stdin readLine v 1 0 8 6 0 0 0 5 0 0 v 0 v 1 v 2 v 3 v 4 v 5 v 6 v 7 v 8 v 9 Consider int v new int 10 int i 7 int j 2 int k 4 v 0 1 v i 5 v j v i 3 v j 1 v i v 0 v v j 12 System out println v 2 v k Integer parseInt stdin readLine v 1 0 8 6 0 0 0 5 12 0 v 0 v 1 v 2 v 3 v 4 v 5 v 6 v 7 v 8 v 9 Consider int v new int 10 int i 7 int j 2 int k 4 v 0 1 v i 5 v j v i 3 8 is displayed v j 1 v i v 0 v v j 12 System out println v 2 v k Integer parseInt stdin readLine v 1 0 8 6 0 0 0 5 12 0 v 0 v 1 v 2 v 3 v 4 v 5 v 6 v 7 v 8 v 9 Consider int v new int 10 int i 7 int j 2 int k 4 v 0 1 v i 5 v j v i 3 Suppose 3 is extracted v j 1 v i v 0 v v j 12 System out println v 2 v k Integer parseInt stdin readLine v 1 0 8 6 3 0 0 5 12 0 v 0 v 1 v 2 v 3 v 4 v 5 v 6 v 7 v 8 v 9 Consider Segment int b new int 100 b 1 0 b 100 0 Causes Array variable to reference a new list of 100 integers Each element is initialized to 0 Two exceptions to be thrown 1 is not a valid index too small 100 is not a valid index too large IndexOutOfBoundsException Consider Point p new Point 3 p 0 new Point 0 0 p 1 new Point 1 1 p 2 new Point 2 2 p 0 setX 1 p 1 setY p 2 getY Point vertex new Point 4 4 p 1 p 0 p 2 vertex Consider Point p new Point 3 p 0 new Point 0 0 p 1 new Point 1 1 p 2 new Point 2 2 p 0 setX 1 p 1 setY p 2 getY Point vertex new Point 4 4 p 1 p 0 p 2 vertex p 0 p 1 p 2 p Point 0 0 Point 1 1 Point 2 2 Consider Point p new Point 3 p 0 new Point 0 0 p 1 new Point 1 1 p 2 new Point 2 2 p 0 setX 1 p 1 setY p 2 getY Point vertex new Point 4 4 p 1 p 0 p 2 vertex p 0 p 1 p 2 p Point 1 0 Point 1 1 Point 2 2 Consider Point p new Point 3 p 0 new Point 0 0 p 1 new Point 1 1 p 2 new Point 2 2 p 0 setX 1 p 1 setY p 2 getY Point vertex new Point 4 4 p 1 p 0 p 2 vertex p 0 p 1 p 2 p Point 1 0 Point 1 2 Point 2 2 Consider Point p new Point 3 p 0 new Point 0 0 p 1 new …
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