Java Reference
In-Depth Information
6.
The various
if
statements all make control decisions based on a
Boolean expression
.
Based on the
true
or
false
evaluation of the expression, these statements take one
of two possible courses.
7.
The
switch
statement makes control decisions based on a switch expression of type
char
,
byte
,
short
,
int
, or
String
.
8.
The keyword
break
is optional in a
switch
statement, but it is normally used at
the end of each case in order to skip the remainder of the
switch
statement. If the
break
statement is not present, the next
case
statement will be executed.
9.
The operators in expressions are evaluated in the order determined by the rules of
parentheses,
operator precedence
, and
operator associativity
.
10.
Parentheses can be used to force the order of evaluation to occur in any sequence.
11.
Operators with higher precedence are evaluated earlier. For operators of the same
precedence, their associativity determines the order of evaluation.
12.
All binary operators except assignment operators are left-associative; assignment
operators are right-associative.
T
EST
Q
UESTIONS
P
ROGRAMMING
E
XERCISES
Pedagogical Note
For each exercise, carefully analyze the problem requirements and design strategies
for solving the problem before coding.
think before coding
Debugging Tip
Before you ask for help, read and explain the program to yourself, and trace it using
several representative inputs by hand or using an IDE debugger. You learn how to
program by debugging your own mistakes.
learn from mistakes
Section 3.2
*3.1
(
Algebra: solve quadratic equations
) The two roots of a quadratic equation
can be obtained using the following formula:
ax
2
+
bx
+
c
=
0
b
2
b
2
r
1
=
-
b
+ 2
-
4
ac
r
2
=
-
b
- 2
-
4
ac
and
2
a
2
a
b
2
is called the discriminant of the quadratic equation. If it is positive, the
equation has two real roots. If it is zero, the equation has one root. If it is negative,
the equation has no real roots.
Write a program that prompts the user to enter values for
a
,
b
, and
c
and displays
the result based on the discriminant. If the discriminant is positive, display two
roots. If the discriminant is
0
, display one root. Otherwise, display “The equation
has no real roots”.
-
4
ac
