全新java初学者实践教程6(Java SE5.0版)
>$^v@jf 基本语法3
JI&ik_k3 Ky6.6Y<.| Ndb_| 我们这个教程侧重的是实践的内容和语言的重点。在[font="Times]java语言中还有很多细节的东西,请参考[font="Times]sun公司的官方培训教程。我们这里不能一一讲述。这节课我们来给大家提供一些程序流程控制的一些例子供大家学习。计算机怎么做事情,是我们教给他的。我们用它解决实际生活中的问题,所以计算机要描述现实生活中的流程。[font="Times]Java语言中提供了[font="Times]4类程序控制语句,来描述流程:
3WH"NC-O< /Q |guJx [font="Times] 1.循环语句[font="Times]:while,do-while,for
4q<LNvJA .)eJL [font="Times]2.分支语句[font="Times]:if-else,switch,
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%+>t @F,GM 3.跳转语句[font="Times] break,continue,label: 和[font="Times]return
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j?eWh#[K" 4.异常处理语句[font="Times]:try-catch-finally,throw
D4';QCwo WnATgY t 实践:
u+U '|6)E [font="Times] 1.循环语句
h ~\bJ*Zp [font="Times] while 语句
]g}Tqf/N% [font="Times]class While {
]t4 9Efw [font="Times]public static void main(String args[]) {
_1<zpHp [font="Times]int n = 10;
G{4~{{tI [font="Times]while(n > 0) {
F0&BEJBkU [font="Times]System.out.println("tick " + n);
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[font="Times]n--;
RU r0K#] [font="Times]}
y2XeD=_' [font="Times]}
CBj&8#8Z [font="Times]}
6Vq]AQx [font="Times] do…while 语句
BK+(Uf;g [font="Times] class DoWhile {
HizMjJ| [font="Times]public static void main(String args[]) {
Muhq,>!U [font="Times]int n = 10;
627xR$U~ [font="Times]do {
sE,Q:@H5 [font="Times]System.out.println("tick " + n);
-~wGJM
VA [font="Times]n--;
]yR0"<W^xO [font="Times]} while(n > 0);
'Dh+v3O [font="Times]}
N sUFM [font="Times]}
n_8wYiBs( 二者区别,[font="Times]do…while至少循环一次,而[font="Times]while的表达式要是为[font="Times]flase的话可以一次也不循环。再通俗一点,[font="Times]do…while就算是括号里的是[font="Times]flase,人家最少也能[font="Times]do一次。
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N7J:Q [font="Times] for语句
rSGt`#E-s. [font="Times] class ForTick {
C^dnkuA [font="Times]public static void main(String args[]) {
Gp<7i5 [font="Times]int n;
;p$KM-?2D [font="Times]for(n=10; n>0; n--)
!i"Z [font="Times]System.out.println("tick " + n);
hqPpRSv' [font="Times]}
)_7OHV *3 [font="Times]}
z3 zN^ZT 与上面那两个的区别,[font="Times]for循环执行的次数是可以在执行之前确定的。通俗一点说吧,看这个例子[font="Times] for(n=10; n>0; n--)就是在括号里的时候,就已经知道要循环[font="Times]10次了。
WJB/X"J 还有啊,[font="Times]for循环的部分可以为空的
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[font="Times]class ForVar {
#7wOr78 [font="Times]public static void main(String args[]) {
#fF~6wopV [font="Times]int i;
ig] hY/uT [font="Times]boolean done = false;
jjs1Vj1@< [font="Times]i = 0;
uude<d"U [font="Times]for( ; !done; ) {
<%@S-+D`] [font="Times]System.out.println("i is " + i);
=f4v: j}'| [font="Times]if(i == 10) done = true;
q;XO1Se [font="Times]i++;
z j[/~I [font="Times]}
!A5UT- [font="Times]}
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循环语句的例子下载
]+ \]2`? [font="Times] 2.分支语句[font="Times]
5>o<!0g [font="Times] if/else语句
2E@ ! [font="Times]class IfElse {
upD2vtU [font="Times]public static void main(String args[]) {
;k<n}shD [font="Times]int month = 4; // April
,$lOQ7R1( [font="Times]String season;
}w,^]fC: [font="Times]if(month == 12 || month == 1 || month == 2)
.6@qU} [font="Times]season = "Winter";
319 &: [font="Times]else if(month == 3 || month == 4 || month == 5)
L} >XH* [font="Times]season = "Spring";
im}= [font="Times]else if(month == 6 || month == 7 || month == 8)
d#?.G3YmK [font="Times]season = "Summer";
'h?;i2[ [font="Times]else if(month == 9 || month == 10 || month == 11)
ujo3"j[b [font="Times]season = "Autumn";
;M<jQntqS{ [font="Times]else
pi'w40!: [font="Times]season = "Bogus Month";
o0f{ePZ= [font="Times]System.out.println("April is in the " + season + ".");
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SQ! [font="Times]}
ZTq"SQ>ym [font="Times]}
3Pb]Of# [font="Times]//这段程序输出[font="Times]:
E"E Bj7<s [font="Times]//April is in the Spring.
ddf#c,SQ [font="Times]// 注意[font="Times] “[font="Times]||”是或运算
,mu=#}a@} [font="Times] switch语句
xz@/^Cj [font="Times] class Switch {
~@3X&E0S [font="Times]public static void main(String args[]) {
h{&X`$ [font="Times]int month = 4;
"`sr# [font="Times]String season;
Z+zx*(X [font="Times]switch (month) {
>bKN$,Qen [font="Times]case 12:
b~M3j& [font="Times]case 1:
**zh>Y}6 [font="Times]case 2:
(c{<JYEC [font="Times]season = "Winter";
%E!^SF?Y [font="Times]break;
Anpx%NVo [font="Times]case 3:
~AD%aHR [font="Times]case 4:
$LS$:%i4 [font="Times]case 5:
3#d5.Ut [font="Times]season = "Spring";
fgb%SIi? [font="Times]break;
~"<AYJlO [font="Times]case 6:
pH?tr [font="Times]case 7:
MZpG1 [font="Times]case 8:
rv(Qz|K@ [font="Times]season = "Summer";
/Dn,;@ZwAi [font="Times]break;
U%swqle4 [font="Times]case 9:
HzW`j"\ [font="Times]case 10:
f}4bnu3 [font="Times]case 11:
KUr}?sdz [font="Times]season = "Autumn";
8=]R6[,fD [font="Times]break;
:r<uH6x| [font="Times]default:
zi^T?<t [font="Times]season = "Bogus Month";
l9U^[;D [font="Times]}
)PM&x [font="Times]System.out.println("April is in the " + season + ".");
qRD]Q [font="Times]}
Z3ucJH/)V [font="Times]}
分支语句代码下载 5LT{]&`9 EF7Y 4lp [font="Times]switch语句适合于条件非常多的逻辑
{=(GY@yU/ 请看上述语句可以混合使用,请看
下载例子