全新java初学者实践教程6(Java SE5.0版)
fU@}]& 基本语法3
kuu9'Sqc'b (aVsp*E kMKI=>s+ 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:
96]lI3c kF3 EJ [font="Times] 1.循环语句[font="Times]:while,do-while,for
P{)H7B> SW(7!` [font="Times]2.分支语句[font="Times]:if-else,switch,
7IBm(# [font="Times]
,r{*o6 3.跳转语句[font="Times] break,continue,label: 和[font="Times]return
r=n|MT^O [font="Times]
%2^C 4.异常处理语句[font="Times]:try-catch-finally,throw
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y#H Fly@"W4a 实践:
0(Y$xg [font="Times] 1.循环语句
&YO5N4X~o [font="Times] while 语句
SOb17:o3| [font="Times]class While {
FRF3V> [font="Times]public static void main(String args[]) {
PtO-%I<N [font="Times]int n = 10;
Vm'ReH [font="Times]while(n > 0) {
(6u<w#u [font="Times]System.out.println("tick " + n);
[
w [font="Times]n--;
[4
g5{eX [font="Times]}
aBr%"&Z.MG [font="Times]}
JnhHV(H [font="Times]}
q\O'r[&V [font="Times] do…while 语句
f<xF+wE [font="Times] class DoWhile {
bVtboHlY [font="Times]public static void main(String args[]) {
^4Tr
@g#]" [font="Times]int n = 10;
C+P}R]cT" [font="Times]do {
R"5/ [font="Times]System.out.println("tick " + n);
[4kx59J3b [font="Times]n--;
$Pzvv`f* [font="Times]} while(n > 0);
]O<Yr' [font="Times]}
Mb\~WUWI [font="Times]}
&
?/h5< 二者区别,[font="Times]do…while至少循环一次,而[font="Times]while的表达式要是为[font="Times]flase的话可以一次也不循环。再通俗一点,[font="Times]do…while就算是括号里的是[font="Times]flase,人家最少也能[font="Times]do一次。
miuJ!Kr' [font="Times] for语句
}tft@,dIC [font="Times] class ForTick {
2-o,4EfHVO [font="Times]public static void main(String args[]) {
P{(m: `N [font="Times]int n;
\b.2f+;3 [font="Times]for(n=10; n>0; n--)
aP8Im1<A [font="Times]System.out.println("tick " + n);
-ud~'<k
[font="Times]}
:eQ@I+ [font="Times]}
mb0${n~fz 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。
\VHi 还有啊,[font="Times]for循环的部分可以为空的
LN?T$H [font="Times]class ForVar {
;ZjQy,H% [font="Times]public static void main(String args[]) {
2s-f?WetbP [font="Times]int i;
(oq(-Wv [font="Times]boolean done = false;
Xe=@I* [font="Times]i = 0;
m %ET!+ [font="Times]for( ; !done; ) {
gD=s~DgN) [font="Times]System.out.println("i is " + i);
"uGJ\ [font="Times]if(i == 10) done = true;
/,Ln)?eD [font="Times]i++;
Zx}=c4I(y [font="Times]}
1Na CGD" [font="Times]}
IZJV6clM [font="Times]}
循环语句的例子下载 3(^9K2.s} [font="Times] 2.分支语句[font="Times]
kt[#@M!} [font="Times] if/else语句
F!pUfF,& [font="Times]class IfElse {
X%`8h_ [font="Times]public static void main(String args[]) {
WRVKh [font="Times]int month = 4; // April
DbPw)aCj [font="Times]String season;
jt3s;U* [font="Times]if(month == 12 || month == 1 || month == 2)
@=Ly#HuUM [font="Times]season = "Winter";
tjDVU7um [font="Times]else if(month == 3 || month == 4 || month == 5)
=:~~RqHl [font="Times]season = "Spring";
k]R O=/ ?M [font="Times]else if(month == 6 || month == 7 || month == 8)
4$IPz7 [font="Times]season = "Summer";
H1\~T [font="Times]else if(month == 9 || month == 10 || month == 11)
&JfyXM[] [font="Times]season = "Autumn";
BqR;d [font="Times]else
!G\1$"T$ [font="Times]season = "Bogus Month";
&\0LR?Nh [font="Times]System.out.println("April is in the " + season + ".");
y::KjB 0 [font="Times]}
(y~da~ [font="Times]}
4yRT!k}o [font="Times]//这段程序输出[font="Times]:
rZJp>Q)s [font="Times]//April is in the Spring.
_<t3~{qUT [font="Times]// 注意[font="Times] “[font="Times]||”是或运算
7:x.08 [font="Times] switch语句
gl]{mUZz} [font="Times] class Switch {
p@cPm8L3 [font="Times]public static void main(String args[]) {
@|-ydm0 [font="Times]int month = 4;
M?}2 [font="Times]String season;
*ZN"+wf\ [font="Times]switch (month) {
Aba6/ [font="Times]case 12:
Qx.E+n\ [font="Times]case 1:
>#!n"i; [font="Times]case 2:
Fi7pq2 [font="Times]season = "Winter";
y;<jE.7>
[font="Times]break;
,j&o H$mW [font="Times]case 3:
=i:?4pIZ [font="Times]case 4:
"DRp4; [font="Times]case 5:
q".l:T%|C} [font="Times]season = "Spring";
"Jv&=zJ [font="Times]break;
~0/=5 dC [font="Times]case 6:
%#7M~RB[ [font="Times]case 7:
IDLA-Vxo [font="Times]case 8:
/x$ jd)C [font="Times]season = "Summer";
HO' ELiZ_q [font="Times]break;
v+Mt/8 [font="Times]case 9:
%eD&2$q* [font="Times]case 10:
ge[\% [font="Times]case 11:
kx'6FkZPIr [font="Times]season = "Autumn";
$#KSvo{otI [font="Times]break;
h!d#=.R [font="Times]default:
YJ3970c/M [font="Times]season = "Bogus Month";
UK_2i(I"e [font="Times]}
^~(bm$4r [font="Times]System.out.println("April is in the " + season + ".");
c?IIaj! [font="Times]}
RCxqqUS\C [font="Times]}
分支语句代码下载 bZ3CJ f&mE f, ;sEV [font="Times]switch语句适合于条件非常多的逻辑
VLQfuh; 请看上述语句可以混合使用,请看
下载例子