全新java初学者实践教程6(Java SE5.0版)
)$Fw<;4 基本语法3
}2y"F@{T a6T!)g ;XY#Jl>tg 我们这个教程侧重的是实践的内容和语言的重点。在[font="Times]java语言中还有很多细节的东西,请参考[font="Times]sun公司的官方培训教程。我们这里不能一一讲述。这节课我们来给大家提供一些程序流程控制的一些例子供大家学习。计算机怎么做事情,是我们教给他的。我们用它解决实际生活中的问题,所以计算机要描述现实生活中的流程。[font="Times]Java语言中提供了[font="Times]4类程序控制语句,来描述流程:
I<lkociUCG yj,+7[) [font="Times] 1.循环语句[font="Times]:while,do-while,for
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yaj1nq!*" [font="Times]2.分支语句[font="Times]:if-else,switch,
w2"]%WS % [font="Times]
7<Ut/1$MI 3.跳转语句[font="Times] break,continue,label: 和[font="Times]return
ohXbA9&(x [font="Times]
Y0'~u+KS`5 4.异常处理语句[font="Times]:try-catch-finally,throw
Sr10ot&ox @ceL9#:uc 实践:
VjSbx'i [font="Times] 1.循环语句
D5T0o"A [font="Times] while 语句
^sZHy4-yK# [font="Times]class While {
/4BYH?* [font="Times]public static void main(String args[]) {
%'F[(VB [font="Times]int n = 10;
Se/]J<] [font="Times]while(n > 0) {
!Je!;mEvI [font="Times]System.out.println("tick " + n);
q[Y*.%~ [font="Times]n--;
YWhS< }^ [font="Times]}
1p>&j%dk [font="Times]}
kJXy) [font="Times]}
Re\V<\$J [font="Times] do…while 语句
MM+nE_9lV [font="Times] class DoWhile {
~xZ)btf [font="Times]public static void main(String args[]) {
am
WIA`n= [font="Times]int n = 10;
Qa16x<Xlm [font="Times]do {
x JzO?a' [font="Times]System.out.println("tick " + n);
. =A| [font="Times]n--;
">I50#bT [font="Times]} while(n > 0);
wCr+/"t [font="Times]}
iV%tn{fc [font="Times]}
@n=FSn6c 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。
5#? HL [font="Times] for语句
9T;l* [font="Times] class ForTick {
QEL3b4Vm [font="Times]public static void main(String args[]) {
1K$8F ~%Z [font="Times]int n;
47/YDy% [font="Times]for(n=10; n>0; n--)
`WU"*HqW [font="Times]System.out.println("tick " + n);
d 7QWK(d [font="Times]}
hzk]kM/OC [font="Times]}
iGeuO[^ 与上面那两个的区别,[font="Times]for循环执行的次数是可以在执行之前确定的。通俗一点说吧,看这个例子[font="Times] for(n=10; n>0; n--)就是在括号里的时候,就已经知道要循环[font="Times]10次了。
F[|aDj@q e 还有啊,[font="Times]for循环的部分可以为空的
|w^nCsv [font="Times]class ForVar {
0wl31k{ [font="Times]public static void main(String args[]) {
r+l3J>:K [font="Times]int i;
q(@hYp#O"3 [font="Times]boolean done = false;
i3y>@$fRL\ [font="Times]i = 0;
'v3>"b [font="Times]for( ; !done; ) {
V@>s]]HMq# [font="Times]System.out.println("i is " + i);
`Axn [font="Times]if(i == 10) done = true;
G5 x%:,n [font="Times]i++;
b!|c:mE9| [font="Times]}
T*C]:=) [font="Times]}
zwX1&rN [font="Times]}
循环语句的例子下载 w0t||qj^>" [font="Times] 2.分支语句[font="Times]
4THGHS^ [font="Times] if/else语句
PAXdIh[] [font="Times]class IfElse {
UG9 Ha [font="Times]public static void main(String args[]) {
,}#l0BY [font="Times]int month = 4; // April
\xaK?_hv [font="Times]String season;
g*#.yC1/ [font="Times]if(month == 12 || month == 1 || month == 2)
gTP0: [font="Times]season = "Winter";
q:v&wb% [font="Times]else if(month == 3 || month == 4 || month == 5)
of:xj$dQ_ [font="Times]season = "Spring";
E^jb#9\R [font="Times]else if(month == 6 || month == 7 || month == 8)
U,u\o@3A [font="Times]season = "Summer";
*XlnEHv [font="Times]else if(month == 9 || month == 10 || month == 11)
<yrl_vl{ [font="Times]season = "Autumn";
'%9e8C| [font="Times]else
q>ps99[= [font="Times]season = "Bogus Month";
-i?-Xj#% [font="Times]System.out.println("April is in the " + season + ".");
|q\:3R_0 [font="Times]}
a2un[$Jq` [font="Times]}
:u53zX[v [font="Times]//这段程序输出[font="Times]:
Q<pL5[00fD [font="Times]//April is in the Spring.
6jtnH'E/ [font="Times]// 注意[font="Times] “[font="Times]||”是或运算
&P{[22dQ [font="Times] switch语句
5Y97?n+6 [font="Times] class Switch {
jz;"]k [font="Times]public static void main(String args[]) {
F.JvMy3 [font="Times]int month = 4;
S2fBZ=V8 [font="Times]String season;
5 eWGX [font="Times]switch (month) {
}%9A+w}o [font="Times]case 12:
Lm }:` [font="Times]case 1:
Fn!kest [font="Times]case 2:
WY%'ps_]< [font="Times]season = "Winter";
=sW(2Im [font="Times]break;
e'z[JG= [font="Times]case 3:
wg=ge]E5 [font="Times]case 4:
M1T)e9k=x [font="Times]case 5:
3 tp'}v [font="Times]season = "Spring";
T/&4lJ^2l^ [font="Times]break;
{aWTT&-N [font="Times]case 6:
q>*+.~ [font="Times]case 7:
]MP6VT [font="Times]case 8:
@ zE>n [font="Times]season = "Summer";
!1}A\S [font="Times]break;
q~=]_PMP [font="Times]case 9:
|^i+Srh [font="Times]case 10:
bEE'50D [font="Times]case 11:
i7w>Nvj] [font="Times]season = "Autumn";
E(oI0*S.5 [font="Times]break;
<x),HTJ [font="Times]default:
z\8Kz ]n~ [font="Times]season = "Bogus Month";
F\Gi;6a [font="Times]}
:)\< [font="Times]System.out.println("April is in the " + season + ".");
$>;U^- #3 [font="Times]}
tQ:)j^\ [font="Times]}
分支语句代码下载 _$?SK id|o (W|Eg [font="Times]switch语句适合于条件非常多的逻辑
w#5^A(NR 请看上述语句可以混合使用,请看
下载例子