Control Statements: Part 1; Assignment, ++ and --Operators - Java: How to Program Early Objects - page 109

The two forms are identical except for the spacing and indentation, which the compiler
ignores. The latter form avoids deep indentation of the code to the right. Such indentation
often leaves little room on a line of source code, forcing lines to be split.
Dangling- else Problem
The Java compiler always associates an else with the immediately preceding if unless told
to do otherwise by the placement of braces ( { and } ). This behavior can lead to what is
referred to as the dangling- else problem . For example,
if (x > 5 )
if (y > 5 )
System.out.println( "x and y are > 5" );
else
System.out.println( "x is <= 5") ;
appears to indicate that if x is greater than 5 , the nested if statement determines whether
y is also greater than 5 . If so, the string "xandyare>5" is output. Otherwise, it appears
that if x is not greater than 5 , the else part of the if … else outputs the string "x is <= 5" .
Beware! This nested if … else statement does not execute as it appears. The compiler ac-
tually interprets the statement as
if (x > 5 )
if (y > 5 )
System.out.println( "x and y are > 5" );
else
System.out.println( "x is <= 5" );
in which the body of the first if is a nested if … else . The outer if statement tests whether
x is greater than 5 . If so, execution continues by testing whether y is also greater than 5 . If
the second condition is true , the proper string— "x and y are > 5" —is displayed. However,
if the second condition is false , the string "x is <= 5" is displayed, even though we know
that x is greater than 5 . Equally bad, if the outer if statement's condition is false, the inner
if … else is skipped and nothing is displayed.
To force the nested if … else statement to execute as it was originally intended, we
must write it as follows:
if (x > 5 )
{
if (y > 5 )
System.out.println( "x and y are > 5") ;
}
else
System.out.println( "x is <= 5" );
The braces indicate that the second if is in the body of the first and that the else is
associated with the first if . Exercises 4.27-4.28 investigate the dangling- else problem
further.
Blocks
The if statement normally expects only one statement in its body. To include several state-
ments in the body of an if (or the body of an else for an if … else statement), enclose
the statements in braces. Statements contained in a pair of braces (such as the body of a