Java Reference
In-Depth Information
K
EY
T
ERMS
anonymous array
238
indexed variable 226
insertion sort 248
linear search 245
off-by-one error
array 224
array initializer 227
binary search 245
garbage collection
230
236
selection sort
248
index
224
C
HAPTER
S
UMMARY
1.
A variable is declared as an
array
type using the syntax
elementType[] arrayRefVar
or
elementType arrayRefVar[]
. The style
elementType[] arrayRefVar
is
preferred, although
elementType arrayRefVar[]
is legal.
2.
Unlike declarations for primitive data type variables, the declaration of an array vari-
able does not allocate any space in memory for the array. An array variable is not a
primitive data type variable. An array variable contains a reference to an array.
3.
You cannot assign elements to an array unless it has already been created. You can
create an array by using the
new
operator with the following syntax:
new element-
Type[arraySize]
.
4.
Each element in the array is represented using the syntax
arrayRefVar[index]
.
An
index
must be an integer or an integer expression.
5.
After an array is created, its size becomes permanent and can be obtained using
arrayRefVar.length
. Since the index of an array always begins with
0
, the last
index is always
arrayRefVar.length - 1
. An out-of-bounds error will occur if
you attempt to reference elements beyond the bounds of an array.
6.
Programmers often mistakenly reference the first element in an array with index
1
,
but it should be
0
. This is called the index
off-by-one error
.
7.
When an array is created, its elements are assigned the default value of
0
for the
numeric primitive data types,
\u0000
for char types, and
false
for
boolean
types.
8.
Java has a shorthand notation, known as the
array initializer
, which combines declar-
ing an array, creating an array, and initializing an array in one statement, using the
syntax
elementType[] arrayRefVar = {value0, value1, ..., valuek}
.
9.
When you pass an array argument to a method, you are actually passing the reference
of the array; that is, the called method can modify the elements in the caller's original
array.
10.
If an array is sorted,
binary search
is more efficient than
linear search
for finding an
element in the array.
11.
Selection sort
finds the smallest number in the list and swaps it with the first element.
It then finds the smallest number remaining and swaps it with the first element in the
remaining list, and so on, until only a single number remains.
