全新java初学者实践教程6(Java SE5.0版)
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,-I 基本语法3
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Sk'}& t'n@yX_ 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:
lPy|>&Yc V8^la'_j [font="Times] 1.循环语句[font="Times]:while,do-while,for
~:ASv>m FK _ ZE> [font="Times]2.分支语句[font="Times]:if-else,switch,
*w+'I*QSt~ [font="Times]
+\eJxyO 3.跳转语句[font="Times] break,continue,label: 和[font="Times]return
\SWTP1 [font="Times]
*uc/| c 4.异常处理语句[font="Times]:try-catch-finally,throw
JrzPDb`m PCviQ!X 实践:
#e'>9T [font="Times] 1.循环语句
g#5R||r [font="Times] while 语句
}"D;?$R! [font="Times]class While {
?I}RX~Tgg [font="Times]public static void main(String args[]) {
fVbjU1N [font="Times]int n = 10;
5\Q Tm; [font="Times]while(n > 0) {
p*;!5;OUR [font="Times]System.out.println("tick " + n);
'nCVjO7o [font="Times]n--;
d^ C@5Pd
< [font="Times]}
[wGj?M} [font="Times]}
%K6veB{M [font="Times]}
c1#0o)q*7 [font="Times] do…while 语句
}`uyOgGg* [font="Times] class DoWhile {
Q5,zs_j [font="Times]public static void main(String args[]) {
3\7MeG`tl [font="Times]int n = 10;
yHeL&H [font="Times]do {
J p'^! [font="Times]System.out.println("tick " + n);
{L-^J`> G [font="Times]n--;
EXDDUqZ5\ [font="Times]} while(n > 0);
L&p R# [font="Times]}
CX|W$b)% [font="Times]}
1d5%(:@ 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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n [font="Times] for语句
%*R, ceuI [font="Times] class ForTick {
EF0v!XW [font="Times]public static void main(String args[]) {
^O07GYF [font="Times]int n;
r,6~%T0 [font="Times]for(n=10; n>0; n--)
> mb}~wx` [font="Times]System.out.println("tick " + n);
j4~(6Imm [font="Times]}
@8L5UT [font="Times]}
RkYdK$|K 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。
Y%KowgP\ 还有啊,[font="Times]for循环的部分可以为空的
`"5Ub,~ [font="Times]class ForVar {
+A}t_u3< [font="Times]public static void main(String args[]) {
%_(vSpk [font="Times]int i;
FM{f{2j [font="Times]boolean done = false;
$ L*gtZ [font="Times]i = 0;
) /raTD [font="Times]for( ; !done; ) {
cl& w/OJ# [font="Times]System.out.println("i is " + i);
6S`_L [font="Times]if(i == 10) done = true;
\<7Bx[/D4 [font="Times]i++;
/Hr|u [font="Times]}
Qit&cnO [font="Times]}
`16'qc [font="Times]}
循环语句的例子下载 1j?P$%p [font="Times] 2.分支语句[font="Times]
wC1pfXa [font="Times] if/else语句
_*mn4n= [font="Times]class IfElse {
m#_BF# [font="Times]public static void main(String args[]) {
AyE*1 FD [font="Times]int month = 4; // April
@{/)k%U [font="Times]String season;
"Z.6@
c7 [font="Times]if(month == 12 || month == 1 || month == 2)
.?Eb{W)^br [font="Times]season = "Winter";
ynIe4b [font="Times]else if(month == 3 || month == 4 || month == 5)
]s\r3I] [font="Times]season = "Spring";
z !K2UTX [font="Times]else if(month == 6 || month == 7 || month == 8)
7HPwlS [font="Times]season = "Summer";
Y{}
ub]i [font="Times]else if(month == 9 || month == 10 || month == 11)
fn}E1w [font="Times]season = "Autumn";
`B%%2p& [font="Times]else
A8%
e_XA [font="Times]season = "Bogus Month";
lc,k-}n [font="Times]System.out.println("April is in the " + season + ".");
"n%j2"TYJj [font="Times]}
u
r$ [font="Times]}
x@NfN*?/+i [font="Times]//这段程序输出[font="Times]:
TU|#Pz7n-Z [font="Times]//April is in the Spring.
2F4<3k!& [font="Times]// 注意[font="Times] “[font="Times]||”是或运算
f_c\uN@f [font="Times] switch语句
o,7|=.-b [font="Times] class Switch {
&~:EmLgv [font="Times]public static void main(String args[]) {
de:@/-| [font="Times]int month = 4;
f"Sp.'@ [font="Times]String season;
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[font="Times]switch (month) {
Y@FYo>0O [font="Times]case 12:
l2F#^=tp [font="Times]case 1:
,rB(WKU [font="Times]case 2:
/YJo"\7 [font="Times]season = "Winter";
01.q9AGy [font="Times]break;
/~,*DH$) [font="Times]case 3:
Ao K9=F} [font="Times]case 4:
$kUB%\` [font="Times]case 5:
[jgVN w""D [font="Times]season = "Spring";
hK?GIbRZ [font="Times]break;
ChiIQWFE [font="Times]case 6:
<B6md
i'R [font="Times]case 7:
- Jaee,P [font="Times]case 8:
"6U0
!.ro@ [font="Times]season = "Summer";
d"|_NG` vr [font="Times]break;
PQaTS*0SXJ [font="Times]case 9:
xlv(PVdn [font="Times]case 10:
Gu$/rb? [font="Times]case 11:
e$9a9twl [font="Times]season = "Autumn";
L^qCE-[ [font="Times]break;
w%L4O;E]*{ [font="Times]default:
fI1CT)0<e [font="Times]season = "Bogus Month";
A7L; ims7 [font="Times]}
byM%D$R [font="Times]System.out.println("April is in the " + season + ".");
P^te [font="Times]}
?`RlYu [font="Times]}
分支语句代码下载 /pF8S!,z d+DO}=] [font="Times]switch语句适合于条件非常多的逻辑
;hQ[- 请看上述语句可以混合使用,请看
下载例子