JHTP自测题_第二章_Java应用、输入、输出及运算符简介



Self-Review Exercises

2.1
Fill in theblanks in each of the following statements:

a) A(n)
{ beginsthe body of every method, and a(n) } ends the body of every method.

b) You can use the ifstatement to make decisions.

c)
// begins anend-of-line comment.

d)
Space characters, newlines  and tabs are called whitespace.

e)
Keywords arereserved for use by Java.

f) Java applicationsbegin execution at
main method .

g) Methods
System.out.print,
System.out.println and
System.out.printf displayinformation in a command window.

2.2
State whethereach of the following is
true
or
false. If
false, explain why.

a) Comments cause thecomputer to print the text after the
//
on the screenwhen the program executes. (False)

b) All variables must begiven a type when they’re declared. (True)

c) Java considers thevariables
number
and
NuMbEr
to be identical. (False)

d) The remainder operator (%)
can be used only withinteger operands. (False)

e) The arithmeticoperators
*,
/,
%,
+
and
-
all have the same level of precedence. (False)

2.3
Writestatements to accomplish each of the following tasks:

a) Declare variables
c,
thisIsAVariable,
q76354
and
number
to be of typeint.

b) Prompt the user toenter an integer.

c) Input an integer andassign the result to
int
variable
value. Assume
Scanner
variable
input
can be used to read a value from the keyboard.

d) Print
"Thisis a Java program"
on one line in the command window. Use method
System.out.println.

e) Print
"Thisis a Java program"
on two lines in the command window. The first line should endwith
Java. Use method
System.out.printf
and two
%s
formatspecifiers.

f) If the variable
number
is not equalto
7, display
"The variable number is not equal to 7".

2.4
Identify andcorrect the errors in each of the following statements:

a)
if (c <7);

System.out.println("c isless than 7");

b)
if (c=>
7)

System.out.println("c isequal to or greater than 7");

2.5
Writedeclarations, statements or comments that accomplish each of the followingtasks:

a) State that a programwill calculate the product of three integers.

b) Create a
Scanner
called
input
that readsvalues from the standard input.

c) Declare the variables
x,
y,
z
and
result
to be of typeint.

d) Prompt the user toenter the first integer.

e) Read the first integerfrom the user and store it in the variable
x.

f) Prompt the user toenter the second integer.

g) Read the secondinteger from the user and store it in the variable
y.

h) Prompt the user toenter the third integer.

i) Read the third integerfrom the user and store it in the variable
z.

j) Compute the product ofthe three integers contained in variables
x,
y
and
z, and assign theresult to the variable
result.

k) Use
System.out.printfto display the message
"Product is"followed by the value of the variable
result.

2.6
Using thestatements you wrote in Exercise 2.5, write a complete program that calculates andprints the product of three integers.