中文Thinking in Java：chap4

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Bruce EckelFG (H I J K ( L ( M N O P A ! Q
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programming languages thus tends to look like that machine.ˇ 3 w Z | ′,; $ X O
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//,c04:SimpleConstructor.java
// Demonstration of a simple constructor,
import com.bruceeckel.simpletest.*;
class Rock {
Rock() { // This is the constructor
System.out.println("Creating Rock");
}
}
public class SimpleConstructor {
static Test monitor = new Test();
public static void main(String[] args) {
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for(int i = 0; i < 10; i++)
new Rock();
monitor.expect(new String[] {
"Creating Rock",
"Creating Rock",
"Creating Rock",
"Creating Rock",
"Creating Rock",
"Creating Rock",
"Creating Rock",
"Creating Rock",
"Creating Rock",
"Creating Rock"
});
}
} ///:~
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new Rock();
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//,c04:SimpleConstructor2.java
// Constructors can have arguments,
import com.bruceeckel.simpletest.*;
class Rock2 {
Rock2(int i) {
System.out.println("Creating Rock number " + i);
}
}
public class SimpleConstructor2 {
static Test monitor = new Test();
public static void main(String[] args) {
for(int i = 0; i < 10; i++)
new Rock2(i);
monitor.expect(new String[] {
"Creating Rock number 0",
"Creating Rock number 1",
"Creating Rock number 2",
"Creating Rock number 3",
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"Creating Rock number 4",
"Creating Rock number 5",
"Creating Rock number 6",
"Creating Rock number 7",
"Creating Rock number 8",
"Creating Rock number 9"
});
}
} ///:~
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Tree t = new Tree(12); // 12-foot tree
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//,c04:Overloading.java
// Demonstration of both constructor
// and ordinary method overloading,
import com.bruceeckel.simpletest.*;
import java.util.*;
class Tree {
int height;
Tree() {
System.out.println("Planting a seedling");
height = 0;
}
Tree(int i) {
System.out.println("Creating new Tree that is "
+ i + " feet tall");
height = i;
}
void info() {
System.out.println("Tree is " + height + " feet
tall");
}
void info(String s) {
System.out.println(s + ",Tree is "
+ height + " feet tall");
}
}
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public class Overloading {
static Test monitor = new Test();
public static void main(String[] args) {
for(int i = 0; i < 5; i++) {
Tree t = new Tree(i);
t.info();
t.info("overloaded method");
}
// Overloaded constructor,
new Tree();
monitor.expect(new String[] {
"Creating new Tree that is 0 feet tall",
"Tree is 0 feet tall",
"overloaded method,Tree is 0 feet tall",
"Creating new Tree that is 1 feet tall",
"Tree is 1 feet tall",
"overloaded method,Tree is 1 feet tall",
"Creating new Tree that is 2 feet tall",
"Tree is 2 feet tall",
"overloaded method,Tree is 2 feet tall",
"Creating new Tree that is 3 feet tall",
"Tree is 3 feet tall",
"overloaded method,Tree is 3 feet tall",
"Creating new Tree that is 4 feet tall",
"Tree is 4 feet tall",
"overloaded method,Tree is 4 feet tall",
"Planting a seedling"
});
}
} ///:~
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//,c04:OverloadingOrder.java
// Overloading based on the order of the arguments,
import com.bruceeckel.simpletest.*;
public class OverloadingOrder {
static Test monitor = new Test();
static void print(String s,int i) {
System.out.println("String," + s + ",int," +
i);
}
static void print(int i,String s) {
System.out.println("int," + i + ",String," +
s);
}
public static void main(String[] args) {
print("String first",11);
print(99,"Int first");
monitor.expect(new String[] {
"String,String first,int,11",
"int,99,String,Int first"
});
}
} ///:~
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//,c04:PrimitiveOverloading.java
// Promotion of primitives and overloading,
import com.bruceeckel.simpletest.*;
public class PrimitiveOverloading {
static Test monitor = new Test();
void f1(char x) { System.out.println("f1(char)"); }
void f1(byte x) { System.out.println("f1(byte)"); }
void f1(short x)
{ System.out.println("f1(short)"); }
void f1(int x) { System.out.println("f1(int)"); }
void f1(long x) { System.out.println("f1(long)"); }
void f1(float x)
{ System.out.println("f1(float)"); }
void f1(double x)
{ System.out.println("f1(double)"); }
void f2(byte x) { System.out.println("f2(byte)"); }
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void f2(short x)
{ System.out.println("f2(short)"); }
void f2(int x) { System.out.println("f2(int)"); }
void f2(long x) { System.out.println("f2(long)"); }
void f2(float x)
{ System.out.println("f2(float)"); }
void f2(double x)
{ System.out.println("f2(double)"); }
void f3(short x)
{ System.out.println("f3(short)"); }
void f3(int x) { System.out.println("f3(int)"); }
void f3(long x) { System.out.println("f3(long)"); }
void f3(float x)
{ System.out.println("f3(float)"); }
void f3(double x)
{ System.out.println("f3(double)"); }
void f4(int x) { System.out.println("f4(int)"); }
void f4(long x) { System.out.println("f4(long)"); }
void f4(float x)
{ System.out.println("f4(float)"); }
void f4(double x)
{ System.out.println("f4(double)"); }
void f5(long x) { System.out.println("f5(long)"); }
void f5(float x)
{ System.out.println("f5(float)"); }
void f5(double x)
{ System.out.println("f5(double)"); }
void f6(float x)
{ System.out.println("f6(float)"); }
void f6(double x)
{ System.out.println("f6(double)"); }
void f7(double x)
{ System.out.println("f7(double)"); }
void testConstVal() {
System.out.println("Testing with 5");
f1(5);f2(5);f3(5);f4(5);f5(5);f6(5);f7(5);
}
void testChar() {
char x = 'x';
System.out.println("char argument:");
f1(x);f2(x);f3(x);f4(x);f5(x);f6(x);f7(x);
}
void testByte() {
byte x = 0;
System.out.println("byte argument:");
f1(x);f2(x);f3(x);f4(x);f5(x);f6(x);f7(x);
}
void testShort() {
short x = 0;
System.out.println("short argument:");
f1(x);f2(x);f3(x);f4(x);f5(x);f6(x);f7(x);
}
void testInt() {
int x = 0;
System.out.println("int argument:");
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f1(x);f2(x);f3(x);f4(x);f5(x);f6(x);f7(x);
}
void testLong() {
long x = 0;
System.out.println("long argument:");
f1(x);f2(x);f3(x);f4(x);f5(x);f6(x);f7(x);
}
void testFloat() {
float x = 0;
System.out.println("float argument:");
f1(x);f2(x);f3(x);f4(x);f5(x);f6(x);f7(x);
}
void testDouble() {
double x = 0;
System.out.println("double argument:");
f1(x);f2(x);f3(x);f4(x);f5(x);f6(x);f7(x);
}
public static void main(String[] args) {
PrimitiveOverloading p =
new PrimitiveOverloading();
p.testConstVal();
p.testChar();
p.testByte();
p.testShort();
p.testInt();
p.testLong();
p.testFloat();
p.testDouble();
monitor.expect(new String[] {
"Testing with 5",
"f1(int)",
"f2(int)",
"f3(int)",
"f4(int)",
"f5(long)",
"f6(float)",
"f7(double)",
"char argument:",
"f1(char)",
"f2(int)",
"f3(int)",
"f4(int)",
"f5(long)",
"f6(float)",
"f7(double)",
"byte argument:",
"f1(byte)",
"f2(byte)",
"f3(short)",
"f4(int)",
"f5(long)",
"f6(float)",
"f7(double)",
"short argument:",
"f1(short)",
"f2(short)",
"f3(short)",
"f4(int)",
"f5(long)",
"f6(float)",
"f7(double)",
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"int argument:",
"f1(int)",
"f2(int)",
"f3(int)",
"f4(int)",
"f5(long)",
"f6(float)",
"f7(double)",
"long argument:",
"f1(long)",
"f2(long)",
"f3(long)",
"f4(long)",
"f5(long)",
"f6(float)",
"f7(double)",
"float argument:",
"f1(float)",
"f2(float)",
"f3(float)",
"f4(float)",
"f5(float)",
"f6(float)",
"f7(double)",
"double argument:",
"f1(double)",
"f2(double)",
"f3(double)",
"f4(double)",
"f5(double)",
"f6(double)",
"f7(double)"
});
}
} ///:~
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//,c04:Demotion.java
// Demotion of primitives and overloading,
import com.bruceeckel.simpletest.*;
public class Demotion {
static Test monitor = new Test();
void f1(char x) { System.out.println("f1(char)"); }
void f1(byte x) { System.out.println("f1(byte)"); }
void f1(short x)
{ System.out.println("f1(short)"); }
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void f1(int x) { System.out.println("f1(int)"); }
void f1(long x) { System.out.println("f1(long)"); }
void f1(float x)
{ System.out.println("f1(float)"); }
void f1(double x)
{ System.out.println("f1(double)"); }
void f2(char x) { System.out.println("f2(char)"); }
void f2(byte x) { System.out.println("f2(byte)"); }
void f2(short x)
{ System.out.println("f2(short)"); }
void f2(int x) { System.out.println("f2(int)"); }
void f2(long x) { System.out.println("f2(long)"); }
void f2(float x)
{ System.out.println("f2(float)"); }
void f3(char x) { System.out.println("f3(char)"); }
void f3(byte x) { System.out.println("f3(byte)"); }
void f3(short x)
{ System.out.println("f3(short)"); }
void f3(int x) { System.out.println("f3(int)"); }
void f3(long x) { System.out.println("f3(long)"); }
void f4(char x) { System.out.println("f4(char)"); }
void f4(byte x) { System.out.println("f4(byte)"); }
void f4(short x)
{ System.out.println("f4(short)"); }
void f4(int x) { System.out.println("f4(int)"); }
void f5(char x) { System.out.println("f5(char)"); }
void f5(byte x) { System.out.println("f5(byte)"); }
void f5(short x)
{ System.out.println("f5(short)"); }
void f6(char x) { System.out.println("f6(char)"); }
void f6(byte x) { System.out.println("f6(byte)"); }
void f7(char x) { System.out.println("f7(char)"); }
void testDouble() {
double x = 0;
System.out.println("double argument:");
f1(x);f2((float)x);f3((long)x);f4((int)x);
f5((short)x);f6((byte)x);f7((char)x);
}
public static void main(String[] args) {
Demotion p = new Demotion();
p.testDouble();
monitor.expect(new String[] {
"double argument:",
"f1(double)",
"f2(float)",
"f3(long)",
"f4(int)",
"f5(short)",
"f6(byte)",
"f7(char)"
});
}
} ///:~
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void f() {}
int f() {}
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//,c04:DefaultConstructor.java
class Bird {
int i;
}
public class DefaultConstructor {
public static void main(String[] args) {
Bird nc = new Bird(); // Default!
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}
} ///:~
,
new Bird();
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class Hat {
Hat(int i) {}
Hat(double d) {}
}
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new Hat();
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class Banana { void f(int i) { /*,.,*/ } }
Banana a = new Banana(),b = new Banana();
a.f(1);
b.f(2);
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Banana.f(a,1);
Banana.f(b,2);
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class Apricot {
void pick() { /*,.,*/ }
void pit() { pick(); /*,.,*/ }
}
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//,c04:Leaf.java
// Simple use of the "this" keyword,
import com.bruceeckel.simpletest.*;
public class Leaf {
static Test monitor = new Test();
int i = 0;
Leaf increment() {
i++;
return this;
}
void print() {
System.out.println("i = " + i);
}
public static void main(String[] args) {
Leaf x = new Leaf();
x.increment().increment().increment().print();
monitor.expect(new String[] {
"i = 3"
});
}
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} ///:~
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//,c04:Flower.java
// Calling constructors with "this."
import com.bruceeckel.simpletest.*;
public class Flower {
static Test monitor = new Test();
int petalCount = 0;
String s = new String("null");
Flower(int petals) {
petalCount = petals;
System.out.println(
"Constructor w/ int arg only,petalCount= "
+ petalCount);
}
Flower(String ss) {
System.out.println(
"Constructor w/ String arg only,s=" + ss);
s = ss;
}
Flower(String s,int petals) {
this(petals);
//! this(s); // Can't call two!
this.s = s; // Another use of "this"
System.out.println("String & int args");
}
Flower() {
this("hi",47);
System.out.println("default constructor (no
args)");
}
void print() {
//! this(11); // Not inside non-constructor!
System.out.println(
"petalCount = " + petalCount + " s = "+ s);
}
public static void main(String[] args) {
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Flower x = new Flower();
x.print();
monitor.expect(new String[] {
"Constructor w/ int arg only,petalCount= 47",
"String & int args",
"default constructor (no args)",
"petalCount = 47 s = hi"
});
}
} ///:~
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Y m?,fl? % A Ac X? (
ˇ v w ;?￠ / 0 c X /? & J
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m 3,& ￠ 3 ￥ 4 Q $ u v (? 8 ˇ X 4 c( 9
m R S T U V A E T U ` (￥KD > (E F F 5 | 3 k? 3 6 7 5 y b ￥K D > (
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3 9 F(?,; m ’ ) 6
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D = < G H I ￥K & ￠ ( M p q N (H I?3 O % & >
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( ’ A H I [ X,B …? ˉ? P F G } ( ; T F
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E F X K? ˉ ’ L,M N R S T U V m Qk ^ E F Y Z ’ _! ( M E F,c 1 O P T fl? R ST U m Q (? ˉA; X J Y Z Q ; R C
Y Z? ˉ
X ; (& ￠ Q Y A m Z Z
% ‘ a ( L C y
# ! R S T U E F m [ $ R S T U V(? 3 ￡( % Y X ; ` ’ D (E
F S ! Q D E R S T U > (3 T B # $ (
p q E F E h E F (Qk >
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X $? ˉ￥K #,3 (￥K v w? r P Y ￥K [?Qk, U X V X / ￥K E Z ·L M ( EF Qk? ( R S T U V? (? < Q m F3 fl? 6 7 (W w
8,% g W w E F E L M ￥K E ‰ ( ·B?￥K M ;? [? g,
(3 T? ￥K D E Z ;
< Q % m
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! " # $ ! " # $ ! " # $ ! " # $
% | & ￠
￥K / p q F& ￠ ( M N 3 & ￠ J u v %
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Y Z $? b 1 c ( M ￥K B &,? ˉ￥K
L M ( 3? Y Z ’ ) N (
L ˉ ( M m,N ￥K (< G H I,?ˉ
( ’ ) *,N Y Z < G H I H I [ X,B N? ; k,3 E F (‘ d ‰ ￥K (§ o [ X,g & ￠,
U e ( A[ ˙ ( ’ ) o (3 % (
>
X *? L M r ￥K +? p q
m Qk ￥K (? ˇ e N R S TU V” f? Qk E F D E u % ! " (g z Q '? E m,R ST U Vu
X ` % < G H I,9?,( h?,R S T U V m cˇ < G H I
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‘ a R S T U? j X a ( %,( g A % CD E F (r A X,k l 4 Q T U R S E S E F (
% & ’ (% & ’ (% & ’ (% & ’ (
4 u? X ; 7
6 r L M?& ￠ ˇ Y r N? < Q m F,m (E F & ￠ ( M
8 n J W? ′ V I( ’ ) X g A
m 3 m o ( p A X % [ currency1? B N g,q r ￥K (* + s currency1
a3 a7 a10 a6? ￥t ￥K X ` u v o ( M? %,& ￠ ( M ￥K v
w Z ); cQk § E F (w x Q $? ˉ￥K 3 ] ( currency1 Y Z FR S T U u v w / b Y currency1? ˉ￥K m y z,& ￠ ( Y Z ’ 9 { k,3 U e (; |
(-,” X [ currency1? ; B N A[ E 1 b 3 1 } Q q ~ 5 % m 3 currency1
-,J,? ; r g 8? q (
k? 3 u v ( #? w? y
//,c04:TerminationCondition.java
// Using finalize() to detect an object that
// hasn't been properly cleaned up,
import com.bruceeckel.simpletest.*;
class Book {
boolean checkedOut = false;
Book(boolean checkOut) {
checkedOut = checkOut;
}
void checkIn() {
checkedOut = false;
}
public void finalize() {
if(checkedOut)
System.out.println("Error,checked out");
}
}
public class TerminationCondition {
static Test monitor = new Test();
public static void main(String[] args) {
Book novel = new Book(true);
// Proper cleanup,
novel.checkIn();
// Drop the reference,forget to clean up,
new Book(true);
// Force garbage collection & finalization,
System.gc();
monitor.expect(new String[] {
"Error,checked out"},Test.WAIT);
}
} ///:~
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* + s currency1 D m (
! ￥K FB 1 R S T U u v w /? T Q
’ ) F? ( M,? m 3 T Q? ˉX
q r * + s currency1 %,U

" Q,-? E F k ^ *? Q N 5
,X Z T? ^ L,[ m ;,b,B ! Y - 9? (
! b ’,? K V (EF ) J,R S T U V
) * +,-,/ 0 1 ) * +,-,/ 0 1) * +,-,/ 0 1) * +,-,/ 0 1
ˉ? m ^ 0 1 P ￥K k F? 8? ( Y Z? 9,
P D m (? k F?( T [ 3 O (?J R S T U V E ′ (d L M ￥K ( z 3 currency1 g $ ( M? ;,m E F (Qk Z,￥E F ( m
,( (y 1 · Y F? E F ( z E § G Fa? E F ( z >
Q $? E P
( ￠ ￡ 3 W ([ ￥K? %? ￠ A Y r ^ 3 4 r,B? ! Q Y s t F3
,( ( m X,A } 3 s [ currency1 ￥K ( M,X ` o ( { ￥K E F,fl? A? ˇ u v r o? (Z r D E
& J (a ( 3? (,9 m 3 C ‰ (‘ ( Q C Q E F? 4 > 8 X 3 d,
F? ; [,? & J X 3 s {? ˉ ( Z T (
fl? r J E F ( * ￥ ;( ′ (
C D O P? @ R S T U V AT UR S ( M,P (￥K c & J P? ˇ { ( o ˙ AI W? ` l
R S T U V” ‰ E F,3 ( m (? 4 e (E F
% ￠ ￡ R S T U V
u,? y 1 (? /,￡ b t ( ￠
3 u v ( %8? (( t A(? m [ ￥K? % # 3
IV [ currency1 m
g ￥K ( M IV,1 [ currency1 m
1 c? b ( M IV,1? ￠
IV,’ L,@ 4 (3 x X′ %? ￠ (?,R S T U V￡? 3 ￥ D m (￥K g
IV? (￥K Qk § E F t m,C Y
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ˉ3 R S ￥K > § - Y 3 currency1 ( Y Ac (
IV X,?,% ˙ R S T U V ! - (￥K % V (a '
’ I? B )￡ QR S T U ( – A j m r
,( O P,b F3 (b t? R S T U X )
I( > § b m | D m,(￥K? v w ; b,g AFa? F?x F(
O? E fi i l ￥K ˉ a? x F? r ￥ D m (; ! c ( B,(￥K g 3
u? ’ g AD ￥K? 9 ’,￥K (
! AD (￥K E fl g? + ￥? H? D ^ ([ ￥K v w? B,(? F m? - (￥K –
/ ˇ(! ",Ac X.,R S,
,( D (? v ( ˇR S T U t,m V g ￥K u R S T U V” § · |? Q NO w? Z ￠ ￥K § * m 3?
ˇ( $ )t? ( ’ p q /? kQ
X 3 mT U t
9 P B,(￥K 3 g 3 /Y R S,‰ ￥K B g ( M 3? 3 ( ) B,,
Y? !,(? 4 9 ￥K 3 r g 3 r ( M D m o A
& J
( p q 1 F x F? ( E … J ; m 3 %?‰ ˇ8 ;,g (
[ o ￥K
,F,g ( M ` 1 E b | F r? u 4 m 3? §
m e ! " D = ( ·T U V
* ˇ( ` X 3? m e 9 F e?Q T r ′ (E F m
,( ^ ′ E F Y j P 3 E F g 3 E F Q ￡ N ! "
! " 3 ˉ ’? O,A,0 ˙ ( 2 3
X 0 R S ·T U V % P 3 E F?( c g 3 E F k l,,¨? 5 ( 0 m
,(,Fq ~ g ’ X ` 0 (R S ( M T? g 3 y 1 ·k
D = (? v ˇ,? 3 y 1 ·ˇ D = ( & ￡
ˇ · @ (,( D ( t F3 X 5 k & ￡ ˇ >? 0 1 ’ 0 ˙ 2 3 X 0 R S ( M A A,
& ￡ ˇ(m [ a? x F? ! ’? D m (
9 ! B,(￥K [ currency1 A g 3 B,(￥K (
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M A” F￥K b 3? ‘ X ^ AX,… J T U ￥K m? ‘ ^ cM N u A8,& ￠ & ￠ ( M,Qk,(￥K AX, D E? ˉR S T U V%,?,? (
( A ; ‰ ￥K, + ˇ(? m ·(R S T U X F m,> T
U R S ( M ’ p q c? kQ F (,V $ R S T U V 3 R? /? ( m < 9 Q A X ( 3 ˙ @ (
,( X > (R S T U V”FE F X K ( M J ‰ & ￡ ˇ[ % ’ /? kQ
c / d g ^ (
,(,′ ′ r E F ′ ￥K,g 3 ˇ )A (E F —( + ˇ% FQk u / P B,(￥K g % > V E F m,
u T U ( M E? l ( ￥K,[? m 3 ‘ Z A ! B,(? IV
ˇ? 5 k m J currency1 R S T U u 8 L M ( 8,B,§ A? ˉF Z r B - ^ (,F IVJ ! Q? ; v V (
￥K,h (& ￠,O @,′ ￥K X,” F IVJ T
,F ￥K (,B,,(,R S TU ( `? ˉD m ￥K O R S T U,3 k l ( A,T? g & ￡ ˇ · ￠
,( [, & ￡ ˇ( `? ˉ? X,A T? T + ˇ D =(? v ˇ,D E t } (? v ( (? +
& ￡ ˇ
,( m V ( ; d ` (r b % ( Y? Vm ( B
0 1? V(,0 1? V” r?c r ’ q
,( (￡ Q,; L,A? ( M
5 k 3 currency1 L M Y (￥K ( M
’,/ g currency1 9 \ * E F E j
0 1? VQ?,Am e,C y3 % 3 C 4 r ￠ F ’ Z,9 Q ‰ A,,’ ( z
\? % 8 h ( 0 1 V;,? E F ( ￥ ` ( —,m 3 D = (?B,a
ˇ(? X g p %( M X 1
0 1? b & 2 ( 3 – O,A ( [ currency1 L,( M? 1 3 C? %?,V A( z [ A
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,,+ F u?,,f % T % h? ˉ + F E O?() +,i? (? — D E ’ y
void f() {
int i;
i++; // Error -- i not initialized
}
,g 3? — #?; m f % 9? V E?
3,? < J } ’ ) (,,? u,P,’ ) d e f % ( } F
ˉ
( ) I Y Z 5 m X,()? ; f %? g I % / F I u ￥A,(f % X Y Z?,9 P R S ;?A[
X c( D E ( (I? ;,3 f Fk? (?y
//,c04:InitialValues.java
// Shows default initial values,
import com.bruceeckel.simpletest.*;
public class InitialValues {
static Test monitor = new Test();
boolean t;
char c;
byte b;
short s;
int i;
long l;
float f;
double d;
void print(String s) { System.out.println(s); }
void printInitialValues() {
print("Data type Initial value");
print("boolean " + t);
print("char [" + c + "]");
print("byte " + b);
print("short " + s);
print("int " + i);
print("long " + l);
print("float " + f);
print("double " + d);
}
public static void main(String[] args) {
InitialValues iv = new InitialValues();
iv.printInitialValues();
/* You could also say,
new InitialValues().printInitialValues();
*/
monitor.expect(new String[] {
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"Data type Initial value",
"boolean false",
"char [" + (char)0 + "]",
"byte 0",
"short 0",
"int 0",
"long 0",
"float 0.0",
"double 0.0"
});
}
} ///:~; < g D m,? Ac? r f %,
(
4 ] ¨ ! Q D E 3 ˙? X,m % z? f % ( Q y 1 (
E?,< g? ˉF?O?,3 ￥K (
% m ￥A,f % Y Z Y
,B? J 3 6 7 ( [
(? 2 3 4 5 62 3 4 5 62 3 4 5 62 3 4 5 6
ˉ%? +? J f % Y w? T 3 u v ( FO
( + ( M j?A X ; F? Z T X ^ V
( o X — k? # $ ( ) I (O? c 1,˙ AFO?I ( M d e f % ( y
class InitialValues {
boolean b = true;
char c = 'x';
byte B = 47;
short s = 0xff;
int i = 999;
long l = 1;
float f = 3.14f;
double d = 3.14159;
//.,,
[ E? ￥fl
(￥K,f %? ˉ% 3 Y Z? E? L M + Y,f % y
class Measurement {
Depth d = new Depth();
//,,,
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ˉ f,,Y Z,g 3 B?
' (L, 2 3 E N Q ˇ f % ( y
class CInit {
int i = f();
//..,
}
9 [ E m I IX ; (§ Ay z f %
( )? E? T y
class CInit {
int i = f();
int j = g(i);
//..,
}
X ;? T y
class CInit {
int j = g(i);
int i = f();
//..,
}
￥? VQ $ F r ￥o -
^ X w ( f % (z’ m Y ’ [ X (
Q,f % s u v m j Am )
# $ (D m ￥K?,g 3 f % m?| % ( V M? % ′ (? B
4 5 6 4 5 6 4 5 6 4 5 6
E G H IQ,f % ; { Q ′ (? B
E N Y FL,,1 E O f % ( m 3currency1 % ‘ a y? m ‰ (f % AFG H IL,u?,D E Q $? ˉ ’ y
class Counter {
int i;
Counter() { i = 7; }
//,,,
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/,B f % 4 9 8 5 ￥) ￥K ( 2 3 O?(?f ( ) I [ X ‰ ( 0? VX,? ; FG H I( Z r,f %? F
u 4,f % f %? m,,i a3 a7 a11 a6
￥ f % (z’ ( + F (O (z’ D N O ( +
(O? ;,￠ F O?( r Y (O?> § + (f %,/ ) 2 3 G H I(N y
//,c04:OrderOfInitialization.java
// Demonstrates initialization order,
import com.bruceeckel.simpletest.*;
// When the constructor is called to create a
// Tag object,you'll see a message,
class Tag {
Tag(int marker) {
System.out.println("Tag(" + marker + ")");
}
}
class Card {
Tag t1 = new Tag(1); // Before constructor
Card() {
// Indicate we're in the constructor,
System.out.println("Card()");
t3 = new Tag(33); // Reinitialize t3
}
Tag t2 = new Tag(2); // After constructor
void f() {
System.out.println("f()");
}
Tag t3 = new Tag(3); // At end
}
public class OrderOfInitialization {
static Test monitor = new Test();
public static void main(String[] args) {
Card t = new Card();
t.f(); // Shows that construction is done
monitor.expect(new String[] {
"Tag(1)",
"Tag(2)",
"Tag(3)",
"Card()",
"Tag(33)",
"f()"
});
}
} ///:~
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c? P ￥K (O? ￠ g & ( r | E f? f %,FJ G H I? 0 ( Z u ‰ G H I ￥
’,,3 f %? E ’ ( ! * < g
’ ( B f %,e currency1 y3 currency1 FG H IN u
3 ￥K B? …,” B 1 R S TU
T ( ` } X Z? % ;,f,(f % 5 | 3 k? ˉ,3 X ￥
’,f % (G H I O?
’ ( M m d e?,? ˇ(f % Y,
￥
I Q $ > (y? ˉA 3? m f % Y Z A” g 3? (
(f %? ˉA 3 ￥K (
Y Z fl? L M 3 (￥K P g Y ￥K ! A
ˉ FO?( M f % Y fl
I Z e?,/L M V ˙ ￥K
I ; m 3 % ￥ I,f % ( M ! " Q,c ’ Q P ! " ' & > y
//,c04:StaticInitialization.java
// Specifying initial values in a class definition,
import com.bruceeckel.simpletest.*;
class Bowl {
Bowl(int marker) {
System.out.println("Bowl(" + marker + ")");
}
void f(int marker) {
System.out.println("f(" + marker + ")");
}
}
class Table {
static Bowl b1 = new Bowl(1);
Table() {
System.out.println("Table()");
b2.f(1);
}
void f2(int marker) {
System.out.println("f2(" + marker + ")");
}
static Bowl b2 = new Bowl(2);
}
class Cupboard {
Bowl b3 = new Bowl(3);
static Bowl b4 = new Bowl(4);
Cupboard() {
System.out.println("Cupboard()");
b4.f(2);
}
void f3(int marker) {
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System.out.println("f3(" + marker + ")");
}
static Bowl b5 = new Bowl(5);
}
public class StaticInitialization {
static Test monitor = new Test();
public static void main(String[] args) {
System.out.println("Creating new Cupboard() in
main");
new Cupboard();
System.out.println("Creating new Cupboard() in
main");
new Cupboard();
t2.f2(1);
t3.f3(1);
monitor.expect(new String[] {
"Bowl(1)",
"Bowl(2)",
"Table()",
"f(1)",
"Bowl(4)",
"Bowl(5)",
"Bowl(3)",
"Cupboard()",
"f(2)",
"Creating new Cupboard() in main",
"Bowl(3)",
"Cupboard()",
"f(2)",
"Creating new Cupboard() in main",
"Bowl(3)",
"Cupboard()",
"f(2)",
"f2(1)",
"f3(1)"
});
}
static Table t2 = new Table();
static Cupboard t3 = new Cupboard();
} ///:~
! ; ˙? < g (L M & F§ (O ￠ L M,
(! ( )? & FO?
( ) u / L M,3 fl (! ’? E ’ ( ! < !
),F % ( M,f %? ˉ? m L M
￥K? H I X ; g (?
) [ X,L M (! ( ) m L M,3
￥K u? 3 currency1 + ! ) ( M Ac 8,B f %
￥K X,` 1 f %,
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ˉ/ m L M ^ ￥K § ( ) y z f % ( f %,/ Z ￠ §
) ` Z ￠ fl (￥K !? f?,3 C
￥L M ￥K ( 1 3 4 M m? (
% y
3 currency1 L M (￥K G H I? & J? 3 currency1+ !
( (?\ ( M ￡ QV” %
g a12
,u c E,? g L M,￥K u,￥D m (
I,f %? 3? ￥K ( M,/,
) (f %
L M ￥K ( M ￥K (G M,/ F? ￥K? K (E F
E F / B & r P ￥K ( ( )? J,? (
￥)I\ > v (
b
,O? ) I D 1 (f %
6.,G H I F? < g ( ;, g > V (B 6 m? ( M; ˙? 6 7 (? ˇP § A(? x f % c? – 9 Q
m B A( ·? (y
class Spoon {
static int i;
static {
i = 47;
}
//,,,
A< J } 3? & J 3 ’ F
( (
(f % 3?,,3 currency1 y 3 currency1 L M (￥K? 3 currency1 + ! (
( ) ( M,? L M ^ Y (￥K
Q $ y
//,c04:ExplicitStatic.java
// Explicit static initialization with the "static"
clause,
import com.bruceeckel.simpletest.*;
class Cup {
Cup(int marker) {
System.out.println("Cup(" + marker + ")");
}
void f(int marker) {
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System.out.println("f(" + marker + ")");
}
}
class Cups {
static Cup c1;
static Cup c2;
static {
c1 = new Cup(1);
c2 = new Cup(2);
}
Cups() {
System.out.println("Cups()");
}
}
public class ExplicitStatic {
static Test monitor = new Test();
public static void main(String[] args) {
System.out.println("Inside main()");
Cups.c1.f(99); // (1)
monitor.expect(new String[] {
"Inside main()",
"Cup(1)",
"Cup(2)",
"f(99)"
});
}
// static Cups x = new Cups(); // (2)
// static Cups y = new Cups(); // (2)
} ///:~
/ ^?
(Y,’ + ! ( (￥K P Q… ˙ A L,?
" (Y,& ( f % ’?,g,? ˉP
" Q… & ( f % X,0,‰ B 3,e,
"? & J? O? x f % L,3 currency1
d e,3 A ( Q f % ￥K (fl ( + k? ^ y
//,c04:Mugs.java
// Java "Instance Initialization."
import com.bruceeckel.simpletest.*;
class Mug {
Mug(int marker) {
System.out.println("Mug(" + marker + ")");
}
void f(int marker) {
System.out.println("f(" + marker + ")");
}
}
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public class Mugs {
static Test monitor = new Test();
Mug c1;
Mug c2;
{
c1 = new Mug(1);
c2 = new Mug(2);
System.out.println("c1 & c2 initialized");
}
Mugs() {
System.out.println("Mugs()");
}
public static void main(String[] args) {
System.out.println("Inside main()");
Mugs x = new Mugs();
monitor.expect(new String[] {
"Inside main()",
"Mug(1)",
"Mug(2)",
"c1 & c2 initialized",
"Mugs()"
});
}
} ///:~
E < g? f %
- ( y
{
c1 = new Mug(1);
c2 = new Mug(2);
System.out.println("c1 & c2 initialized");
}
,m
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F
f % I– 3 currency1 s? R S ! ( D = (? w f %
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Q O? ( % O?3 I– % j F ( \? J 3 ￥? ( $?,,y
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int[] a1;
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int a1[];
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VX *? # AI– m V ′ ˙ c T g,?
ˇ " F? D g ( 3 I– (
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% ˙ AFL M I– ( M,f % 6 7 (f % 3￥ $? P $9 Q F 5 k E F,(? V
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int[] a1 = { 1,2,3,4,5 };
Y Z Z % F m I– (5 k O?3 I– (

int[] a2;
‰
E 3 I– 3? E $
a2 = a1;
FT (
D ^ (y
//,c04:Arrays.java
// Arrays of primitives,
import com.bruceeckel.simpletest.*;
public class Arrays {
static Test monitor = new Test();
public static void main(String[] args) {
int[] a1 = { 1,2,3,4,5 };
int[] a2;
a2 = a1;
for(int i = 0; i < a2.length; i++)
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a2[i]++;
for(int i = 0; i < a1.length; i++)
System.out.println(
"a1[" + i + "] = " + a1[i]);
monitor.expect(new String[] {
"a1[0] = 2",
"a1[1] = 3",
"a1[2] = 4",
"a1[3] = 5",
"a1[4] = 6"
});
}
} ///:~
E < g
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m C ( yD m I–
X / A ( ￥K (? m3 e r (E )? X ; A” #? I– mV ˙ < = )
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,
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( " 9 [ currency1 + !I– ( M? % 4 q r Y [,? P A,[ $? ˉ ` fl? % Y Z + ! I– ;,’ `
(3 =,0 ( c ’ ) (? ` (b c - (
ˉ? ’ ( M X 0 1 I– % m V ˙ < = Y w Z E
j Q L M I– (< = 2 3 ; L M (I–
X ; )L M fl I– ( y
//,c04:ArrayNew.java
// Creating arrays with new,
import com.bruceeckel.simpletest.*;
import java.util.*;
public class ArrayNew {
static Test monitor = new Test();
static Random rand = new Random();
public static void main(String[] args) {
int[] a;
a = new int[rand.nextInt(20)];
System.out.println("length of a = " + a.length);
for(int i = 0; i < a.length; i++)
System.out.println("a[" + i + "] = " + a[i]);
monitor.expect(new Object[] {
"%% length of a = \\d+",
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new TestExpression("%% a\\[\\d+\\] = 0",
a.length)
});
}
} ///:~
(
m y -
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- X ; ˙ X p % ( Y ; FL,` § (currency1 I }
I– (′ (
,#? (,T 3? g Y Iu 4 ( ( )A? 0 ( & > I–? & J FL,L M ( ‰ ’ ( ! [ f?,
(I– < =,B f % ˇ
￥)I\? ￥)
9 I– (O? f % [ E w 3 y
int[] a = new int[rand.nextInt(20)];
ˉ E ( v w? / (
ˉ? % Z ￠ (X
I– ￥K I– Y? p q
,(! " Q,? L M ( 3
(I– | 3 k # A X
y
//,c04:ArrayClassObj.java
// Creating an array of nonprimitive objects,
import com.bruceeckel.simpletest.*;
import java.util.*;
public class ArrayClassObj {
static Test monitor = new Test();
static Random rand = new Random();
public static void main(String[] args) {
Integer[] a = new Integer[rand.nextInt(20)];
System.out.println("length of a = " + a.length);
for(int i = 0; i < a.length; i++) {
a[i] = new Integer(rand.nextInt(500));
System.out.println("a[" + i + "] = " + a[i]);
}
monitor.expect(new Object[] {
"%% length of a = \\d+",
new TestExpression("%% a\\[\\d+\\] = \\d+",
a.length)
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});
}
} ///:~
I– (L M 2 3 E k F
(? y
Integer[] a = new Integer[rand.nextInt(20)];
3
(I– D E % m L M (# ￥KQ f %
f % (^ m M N y
a[i] = new Integer(rand.nextInt(500));
9? ˉ? *,L M ￥K Y Z ’ L,( M? % g I– (?
( M,g 3? c Q < < ] ¨ (
￥K (G?,< g # ￥K (
,B r? ^ ( [ E 3 ( $? $9 Q (￥K? Q f % ￥K I– Am e
·y
//,c04:ArrayInit.java
// Array initialization,
public class ArrayInit {
public static void main(String[] args) {
Integer[] a = {
new Integer(1),
new Integer(2),
new Integer(3),
};
Integer[] b = new Integer[] {
new Integer(1),
new Integer(2),
new Integer(3),
};
}
} ///:~
3 ·; ) V W w A()? ′ I– (′ F?
( M? O,? (b 3? ( 6 ;? ( y 1 u v 3
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·d e,3 u ( ; g ( I?
[ B (? ˇ ( ˉ( L M N ( As ; ) II+ z 0 (W w [ ; ) I z 0 (Ww ( )D m (? @? K (
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E L M 3 / 0 I– 1 I( 9? N y
//,c04:VarArgs.java
// Using array syntax to create variable argument
lists,
import com.bruceeckel.simpletest.*;
class A { int i; }
public class VarArgs {
static Test monitor = new Test();
static void print(Object[] x) {
for(int i = 0; i < x.length; i++)
System.out.println(x[i]);
}
public static void main(String[] args) {
print(new Object[] {
new Integer(47),new VarArgs(),
new Float(3.14),new Double(11.11)
});
print(new Object[] {"one","two","three" });
print(new Object[] {new A(),new A(),new A()});
monitor.expect(new Object[] {
"47",
"%% VarArgs@\\p{XDigit}+",
"3.14",
"11.11",
"one",
"two",
"three",
new TestExpression("%% A@\\p{XDigit}+",3)
});
}
} ///:~
,< g
3 / 0 I– 1 I A” ￥? I– `P ￥K? ] ¨ ! Q? (
4 ; 0 R S ￠ ￡ ( !?D L M (
1 $ 1 (￥K,/ ] ¨ ( \ 9
6 ˉ? E h 3 ^ 7 I( · 2 3 4 % 5 b Y
^,m 3?V 7 (I\ ) § ( 1 b? X O? (
c E,' ( ]¨ ( \ 9 ￥K (r?; ˙? R S r L M V I– y
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//,c04:MultiDimArray.java
// Creating multidimensional arrays,
import com.bruceeckel.simpletest.*;
import java.util.*;
public class MultiDimArray {
static Test monitor = new Test();
static Random rand = new Random();
public static void main(String[] args) {
int[][] a1 = {
{ 1,2,3,},
{ 4,5,6,},
};
for(int i = 0; i < a1.length; i++)
for(int j = 0; j < a1[i].length; j++)
System.out.println(
"a1[" + i + "][" + j + "] = " + a1[i][j]);
// 3-D array with fixed length,
int[][][] a2 = new int[2][2][4];
for(int i = 0; i < a2.length; i++)
for(int j = 0; j < a2[i].length; j++)
for(int k = 0; k < a2[i][j].length; k++)
System.out.println("a2[" + i + "][" + j +
"][" +
k + "] = " + a2[i][j][k]);
// 3-D array with varied-length vectors,
int[][][] a3 = new int[rand.nextInt(7)][][];
for(int i = 0; i < a3.length; i++) {
a3[i] = new int[rand.nextInt(5)][];
for(int j = 0; j < a3[i].length; j++)
a3[i][j] = new int[rand.nextInt(5)];
}
for(int i = 0; i < a3.length; i++)
for(int j = 0; j < a3[i].length; j++)
for(int k = 0; k < a3[i][j].length; k++)
System.out.println("a3[" + i + "][" + j +
"][" +
k + "] = " + a3[i][j][k]);
// Array of nonprimitive objects,
Integer[][] a4 = {
{ new Integer(1),new Integer(2)},
{ new Integer(3),new Integer(4)},
{ new Integer(5),new Integer(6)},
};
for(int i = 0; i < a4.length; i++)
for(int j = 0; j < a4[i].length; j++)
System.out.println("a4[" + i + "][" + j +
"] = " + a4[i][j]);
Integer[][] a5;
a5 = new Integer[3][];
for(int i = 0; i < a5.length; i++) {
a5[i] = new Integer[3];
for(int j = 0; j < a5[i].length; j++)
a5[i][j] = new Integer(i * j);
}
for(int i = 0; i < a5.length; i++)
for(int j = 0; j < a5[i].length; j++)
System.out.println("a5[" + i + "][" + j +
"] = " + a5[i][j]);
// Output test
int ln = 0;
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for(int i = 0; i < a3.length; i++)
for(int j = 0; j < a3[i].length; j++)
for(int k = 0; k < a3[i][j].length; k++)
ln++;
monitor.expect(new Object[] {
"a1[0][0] = 1",
"a1[0][1] = 2",
"a1[0][2] = 3",
"a1[1][0] = 4",
"a1[1][1] = 5",
"a1[1][2] = 6",
new TestExpression(
"%% a2\\[\\d\\]\\[\\d\\]\\[\\d\\] = 0",16),
new TestExpression(
"%% a3\\[\\d\\]\\[\\d\\]\\[\\d\\] = 0",ln),
"a4[0][0] = 1",
"a4[0][1] = 2",
"a4[1][0] = 3",
"a4[1][1] = 4",
"a4[2][0] = 5",
"a4[2][1] = 6",
"a5[0][0] = 0",
"a5[0][1] = 0",
"a5[0][2] = 0",
"a5[1][0] = 0",
"a5[1][1] = 1",
"a5[1][2] = 2",
"a5[2][0] = 0",
"a5[2][1] = 2",
"a5[2][2] = 4"
});
}
} ///:~
] ¨ ’,
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int[][] a1 = {
{ 1,2,3,},
{ 4,5,6,},
};
– $,P? { k3? I–
^,
Q 3 L I– I– 3 currency1 (y
int[][][] a2 = new int[2][2][4];
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int[][][] a3 = new int[rand.nextInt(7)][][];
for(int i = 0; i < a3.length; i++) {
a3[i] = new int[rand.nextInt(5)][];
for(int j = 0; j < a3[i].length; j++)
a3[i][j] = new int[rand.nextInt(5)];
}
3
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currency1 (,< = § L z N ! " ;?,L
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r f % E A (~? Q Z ￠ fl
(￥K I– ^ F A $? P V
·?– 9 Q y
Integer[][] a4 = {
{ new Integer(1),new Integer(2)},
{ new Integer(3),new Integer(4)},
{ new Integer(5),new Integer(6)},
};
^,? 3 3 r L M fl
(￥K I– y
Integer[][] a5;
a5 = new Integer[3][];
for(int i = 0; i < a5.length; i++) {
a5[i] = new Integer[3];
for(int j = 0; j < a5[i].length; j++)
a5[i][j] = new Integer(i*j);
}
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,
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