Java Reference
In-Depth Information
expressions are guaranteed to be evaluated in order from left to right (which
matters if any of the arguments have side effects).
Lambda expression (
→
)
A
lambda expression
is an anonymous collection of executable Java code, essen‐
tially a method body. It consists of a method argument list (zero or more
comma-separated expressions contained within parentheses) followed by the
lambda
arrow
operator followed by a block of Java code. If the block of code
comprises just a single statement, then the usual curly braces to denote block
boundaries can be omitted.
Object creation (
new
)
In Java, objects (and arrays) are created with the
new
operator, which is fol‐
lowed by the type of the object to be created and a parenthesized list of argu‐
ments to be passed to the object
constructor
. A constructor is a special block of
code that initializes a newly created object, so the object creation syntax is simi‐
lar to the Java method invocation syntax. For example:
new
ArrayList
();
new
Point
(
1
,
2
)
Type conversion or casting (
()
)
As we've already seen, parentheses can also be used as an operator to perform
narrowing type conversions, or casts. The first operand of this operator is the
type to be converted to; it is placed between the parentheses. The second
operand is the value to be converted; it follows the parentheses. For example:
(
byte
)
28
// An integer literal cast to a byte type
(
int
)
(
x
+
3.14f
)
// A floating-point sum value cast to an integer
(
String
)
h
.
get
(
k
)
// A generic object cast to a string
Statements
A
statement
is a basic unit of execution in the Java language—it expresses a single
piece of intent by the programmer. Unlike expressions, Java statements do not have
a value. Statements also typically contain expressions and operators (especially
assignment operators) and are frequently executed for the side effects that they
cause.
Many of the statements defined by Java are flow-control statements, such as condi‐
tionals and loops, that can alter the default, linear order of execution in well-defined
ways.
Table 2-5
summarizes the statements defined by Java.
