全新java初学者实践教程6(Java SE5.0版)
3koXM_4_{) 基本语法3
C,!}WB@VME E(&GZ QE G2,r%|7ta 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:
{vJ)!'Eh DB>Y#2j4h [font="Times] 1.循环语句[font="Times]:while,do-while,for
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K;`) ;\$P;-VY [font="Times]2.分支语句[font="Times]:if-else,switch,
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Q:x:k+O- 3.跳转语句[font="Times] break,continue,label: 和[font="Times]return
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vsM] <t 4.异常处理语句[font="Times]:try-catch-finally,throw
!j3V'XU#Zn yT>t[t60/S 实践:
Q l$t [font="Times] 1.循环语句
v0dFP0.;& [font="Times] while 语句
f~.w2Cna [font="Times]class While {
/~LXY<-( [font="Times]public static void main(String args[]) {
ecH-JPm' [font="Times]int n = 10;
hCLXL [font="Times]while(n > 0) {
QxGQF| [font="Times]System.out.println("tick " + n);
p]zYj >e [font="Times]n--;
i~IQlyGr. [font="Times]}
B9Dh^9?L [font="Times]}
;
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W].P(A>m [font="Times] do…while 语句
,Dz2cR6 [font="Times] class DoWhile {
#c0
dZ [font="Times]public static void main(String args[]) {
l}DCK [font="Times]int n = 10;
IKK<D'6 [font="Times]do {
8O]U&A@ [font="Times]System.out.println("tick " + n);
lbES9o5 [font="Times]n--;
:`Kr|3bQ [font="Times]} while(n > 0);
@HfWAFT [font="Times]}
:8_`T$8i4 [font="Times]}
{tE/Jv $ 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。
%(-YOTDr [font="Times] for语句
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[font="Times] class ForTick {
i;0`d0^ [font="Times]public static void main(String args[]) {
,<lxq<1I [font="Times]int n;
OU(z};Is6Z [font="Times]for(n=10; n>0; n--)
K;f'&9-+i, [font="Times]System.out.println("tick " + n);
?;,Al`/^ [font="Times]}
fJCh [font="Times]}
G5Ci"0 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。
k"SmbFn%N0 还有啊,[font="Times]for循环的部分可以为空的
bH41#B [font="Times]class ForVar {
eh'mSf^=p [font="Times]public static void main(String args[]) {
/S;o2\ [font="Times]int i;
xaerMr [font="Times]boolean done = false;
wS2iyrIB [font="Times]i = 0;
>:]fN61# [font="Times]for( ; !done; ) {
xQ7n$.?y@ [font="Times]System.out.println("i is " + i);
,h2q37 [font="Times]if(i == 10) done = true;
We]X+>BlO [font="Times]i++;
~MY(6P [font="Times]}
13Z6dhZu [font="Times]}
;f-|rC_" [font="Times]}
循环语句的例子下载 W4CI=94 [font="Times] 2.分支语句[font="Times]
$/C<^}A [font="Times] if/else语句
oQDOwM, [font="Times]class IfElse {
JLAg-j2 [font="Times]public static void main(String args[]) {
#{0DpSzE5 [font="Times]int month = 4; // April
81_3{OrE< [font="Times]String season;
Vk_*]wU [font="Times]if(month == 12 || month == 1 || month == 2)
|Z;wk& [font="Times]season = "Winter";
$EJ*x$ [font="Times]else if(month == 3 || month == 4 || month == 5)
|?Q(4(D`* [font="Times]season = "Spring";
&Jj> jCg [font="Times]else if(month == 6 || month == 7 || month == 8)
E|9LUPcb [font="Times]season = "Summer";
YeJ95\jf [font="Times]else if(month == 9 || month == 10 || month == 11)
g]xZ^M+ [font="Times]season = "Autumn";
6\,^MI [font="Times]else
t%z7#}9$ [font="Times]season = "Bogus Month";
IQ{Xj3;?y [font="Times]System.out.println("April is in the " + season + ".");
V8&/O)} o [font="Times]}
MatC2-aV1 [font="Times]}
bT-G<h*M [font="Times]//这段程序输出[font="Times]:
(?\ZN+V) [font="Times]//April is in the Spring.
4Sg!NPuu7& [font="Times]// 注意[font="Times] “[font="Times]||”是或运算
cM4?Ggn [font="Times] switch语句
\| >eG u [font="Times] class Switch {
"tIf$z [font="Times]public static void main(String args[]) {
savz>E& [font="Times]int month = 4;
:,q3?l6 [font="Times]String season;
~+7yi4(i [font="Times]switch (month) {
g}^/8rW [font="Times]case 12:
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