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head first java shapensone 习题解答.pdf
1 Part One
h
g
Sharpen Solutions
g
You didn’t think we’d
just leave you hanging, did you?
No, we thought we’d be all nice
and helpful with this fi rst book,
to get you hooked, and then
slam you in the next one...
Sometimes there’s more than one right answer. And sometimes the
answer is whatever you want it to be. If you don’t like our answers, argue with us. If we’re
just plain wrong, we’ll change it and give you credit on the web site. If you’re wrong, we’ll
publicly humiliate you, using a very large font.
Just kidding.
Please share your ideas and solutions with us, and we’ll add them with your name (unless
you want to be anonymous, and who could blame you.)
this is a new chapter
1
chapter one
Page 4
int size = 27;
String name = “Fido”;
Dog myDog =
new Dog(name, size);
x = size - 5;
if (x < 15) myDog.bark(8);
while (x > 3) {
myDog.play();
declare an integer variable named ‘size’ and give it the value 27
declare a String variable named ‘name’ and give it the String value “Fido”
declare a Dog variable named ‘myDog’ and give it a new Dog (that has a name and a size)
subtract 5 from the current value of the variable ‘size’, assign the result to the variable ‘x’
if the value of x is less than 15, then tell myDog to bark 8 times
as long as the value of x is greater than 3, tell myDog to play
Page 11
Given the output:
% java Test
DooBeeDooBeeDo
Fill in the missing code:
public class DooBee {
public static void main (String[] args) {
int x = 1;
3
while (x < _____ ) {
print
print
System.out._________(“Doo”);
System.out._________(“Bee”);
x = x + 1;
}
if (x == ______ ) {
3
System.out.print(“Do”);
}
}
}
2
Sharpen Your Pencil - Part One
Head First Java Sharpen Solutions
chapter two
Page 32
Television
int channel
int volume
boolean power
setChannel()
setVolume()
setPower()
skipCommercials()
searchForSimpsons()
Page 35
MOVIE
title
genre
rating
playIt()
Gone with the Stock
Tragic
-2
Lost in Cubicle Space
Comedy
5
Byte Club
Tragic but ultimately uplifting
127
you are here 4
3
object1object2object3titlegenreratingtitlegenreratingtitlegenrerating
Page 50
What is the current value of
pets[2]? ___________
null
What code would make
pets[3] refer to one of the
two existing Dog objects?
_______________________
pets[3] = pets[0]
chapter three
Page 50
Circle the legal statements
from the following list:
1. int x = 34.5;
2. boolean boo = x;
3. int g = 17;
4. int y = g;
5. y = y + 10;
6. short s;
7. s = y;
8. byte b = 3;
9. byte v = b;
10. short n = 12;
11. v = n;
12. byte k = 128;
13. int p = 3 * g + y;
4
Sharpen Your Pencil - Part One
chapter four
Page 85
What’s legal?
Given the method below, which
of the method calls listed on the
right are legal?
Put a checkmark next to the
ones that are legal. (Some
statements are there to assign
values used in the method calls).
int calcArea(int height, int width) {
return height * width;
int f = calcArea(t,17);
int g = calcArea();
calcArea();
need two args
byte h = calcArea(4,20);
}
int j = calcArea(2,3,5);
Head First Java Sharpen Solutions
int a = calcArea(7, 12);
short c = 7;
calcArea(c,15);
int d = calcArea(57);
need two args
calcArea(2,3);
long t = 42;
‘t’ is a long (too big for the int
parameter ‘height’)
need two args
calcArea returns an int,
not a byte
need two args
you are here 4
5
chapter five
Page 101
In the next couple of pages we implement the SimpleDotCom class,
and then later we return to the test class. Looking at our test code
above, what else should be added? What are we not testing in this
code, that we should be testing for? Write your ideas (or lines of
code) below:
Make a fake user guess that is a MISS instead of a hit
Try all three hits
Try out a range of guesses
Try duplicate guesses
(these are just a few...)
Page 105
Turn the to the next page in your book (106) for the answer. But then,
you obviously know that already. We just put this in for completeness.
Didn’t want you thinking we just skipped it. Although we actually are
skipping it. Here in the solutions document, anyway, not in the real
book. You know what we mean.
Page 111
It’s a cliff-hanger!
Will we find the bug?
Will we fix the bug?
Will Ben marry J-Lo?
Stay tuned for the next chapter, where we answer
these questions and more...
And in the meantime, see if you can come up with
ideas for what went wrong and how to fix it.
The current version of the game cares only about the NUMBER
of hits, not what the actual hits really are. So entering the
same number (as long as it’s a hit) three times is the same as
entering the three correct, but different, numbers corresponding
to the three hit locations.
So, we need to somehow keep track of each hit, and maybe
“cross it off the list” to show that it’s been hit and is no longer
a valid entry.
6
Sharpen Your Pencil - Part One
chapter six
Page 130
Turn to page 132 in your book for the answer.
Page 141
Head First Java Sharpen Solutions
We didn’t do an answer for this one, but nobody around here can
remember why. Must have been some excuse about how that makes
it more of a “learning opportunity” for you. If you’ve got an answer
you want to “share” with others (for that warm fuzzy feeling and good
karma points), let us know and we’ll include it (with your name).
[ K at hy , t h i s l o o ks p re t t y w e a k h e re fo r c h a p t e r s i x .
i k e w e ’ re g i v i n g t h e m A N Y T H I N G ! D o n ’ t y o u
D o e s n ’ t l o o k l
fe e l g u i
l t y a b o u t t h at ? — B e r t ]
[ No. —Kathy ]
you are here 4
7
chapter seven
Page 165
How many instance variables does
Surgeon have?
1
How many instance variables does
FamilyDoctor have?
2
How many methods does Doctor have?
How many methods does Surgeon have?
1
2
How many methods does FamilyDoctor
have?
2
Can a FamilyDoctor do treatPatient()?
Can a FamilyDoctor do makeIncision()?
Yes
No
Page 172
Fan
Musician
Rock Star
concert
Pianist
Bass Player
i f
o
r
s
r
e
s
a
b
a
o
a
r
o
r
e
v
w h
k
c
s ,
s
r
e
8 w h
e
r
o
e
o
u
s t
e
r
p l a
e
t
y
a
k
p
c
s
a
h
a
y
r
I
b
s
a
e
e
I
k
w h
r
e
y
p l a
y
p l a
s
s
a
b
o
n
n d
a
s ,
u
o
y
d o
t
o
y
r :
s w e
b
a l k
t
a
n
h i n
t
s
s
a
a
I S
a
s t
w h
[
r
a
a
w e
c
o
r
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o
p
r
a
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o
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N o
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r
e
r
a ll
t
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d o
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k
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e ... w h
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e
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8
Sharpen Your Pencil - Part One
Page 175
Put a check next to the relationships that
make sense.
Oven extends Kitchen
Guitar extends Instrument
Person extends Employee
Ferrari extends Engine
FriedEgg extends Food
Beagle extends Pet
Container extends Jar
Metal extends Titanium
What if I want
Beagle to extend
Dog, but not all
dogs are pets?
(chapter 8)
GratefulDead extends Band
Blonde extends Smart
Beverage extends Martini
Hint: apply the IS-A test
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