14

C H A P T E R

Blocks and Statements

He was not merely a chip of the old block, but the old block itself.

 Edmund Burke

, On Pitt's First Speech

T

HE sequence of execution of a Java program is controlled by

statements

,

which are executed for their effect and do not have values.

Some statements

contain

 other statements as part of their structure; such other

statements are substatements of the statement. We say that statement

S

immediately contains

 statement

U

 if there is no statement

T

 different from

S

 and

U

such that

S

 contains

T

 and

T

 contains

U

. In the same manner, some statements

contain expressions ( 15) as part of their structure.

The first section of this chapter discusses the distinction between normal and

abrupt completion of statements ( 14.1). Most of the remaining sections explain

the various kinds of statements, describing in detail both their normal behavior

and any special treatment of abrupt completion.

Blocks are explained first ( 14.2), because they can appear in certain places

where other kinds of statements are not allowed, and because one other kind of

statement, a local variable declaration statement ( 14.3), must be immediately

contained within a block.

Next a grammatical maneuver is explained that sidesteps the familiar  dan 

gling

else

  problem ( 14.4).

Statements that will be familiar to C and C++ programmers are the empty

( 14.5), labeled ( 14.6), expression ( 14.7),

if

 ( 14.8),

switch

 ( 14.9),

while

( 14.10),

do

 ( 14.11),

for

 ( 14.12),

break

 ( 14.13),

continue

 ( 14.14), and

return

 ( 14.15) statements.

Unlike C and C++, Java has no

goto

 statement. However, the

break

 and

con 

tinue

 statements are extended in Java to allow them to mention statement labels.

The Java statements that are not in the C language are the

throw

 ( 14.16),

synchronized

 ( 14.17), and

try

 ( 14.18) statements.

The last section ( 14.19) of this chapter addresses the requirement that every

statement be

reachable

 in a certain technical sense.

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