全新java初学者实践教程6(Java SE5.0版)
a7%]Y}$ 基本语法3
;i+#fQO7Q %D "I mpJ#:}n 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:
0#^v{DC QkC(uS [font="Times] 1.循环语句[font="Times]:while,do-while,for
>b4eL59 h@@=M [font="Times]2.分支语句[font="Times]:if-else,switch,
7. ;3e@s [font="Times]
H}
g{Cr"Ex 3.跳转语句[font="Times] break,continue,label: 和[font="Times]return
~61v5@ [font="Times]
geCM<] 4.异常处理语句[font="Times]:try-catch-finally,throw
,s;UfF z2>lI9D4V 实践:
Ooy7*W'; [font="Times] 1.循环语句
SasJic2M [font="Times] while 语句
UFuX@Lu0 [font="Times]class While {
(dSL7nel;L [font="Times]public static void main(String args[]) {
<2qr}K{'A [font="Times]int n = 10;
sD wqH.L [font="Times]while(n > 0) {
"snw4if [font="Times]System.out.println("tick " + n);
wj0\$NQ=x [font="Times]n--;
4HA<P6L [font="Times]}
cExS7~* [font="Times]}
q'82qY [font="Times]}
!C:$?oU [font="Times] do…while 语句
'!$Rw"K. [font="Times] class DoWhile {
n.0fVV-A [font="Times]public static void main(String args[]) {
v_-dx [font="Times]int n = 10;
JaGtsi9%. [font="Times]do {
D,FkB"ZZE [font="Times]System.out.println("tick " + n);
ea')$gR [font="Times]n--;
,nm*q#R,0 [font="Times]} while(n > 0);
D}X\Ca"h [font="Times]}
S^ \Vgi( [font="Times]}
04=c-~&q 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。
3:i@II [font="Times] for语句
@I!0-OjL [font="Times] class ForTick {
b1?'gn~ [font="Times]public static void main(String args[]) {
0:Ol7 [font="Times]int n;
!Q0w\j h [font="Times]for(n=10; n>0; n--)
A~t
j/yq9 [font="Times]System.out.println("tick " + n);
,DkNLE [font="Times]}
j8lb~0JD [font="Times]}
,nDaqQ-C!! 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。
"1M[5\Ax 还有啊,[font="Times]for循环的部分可以为空的
r\V
={p [font="Times]class ForVar {
@6T/Tdz [font="Times]public static void main(String args[]) {
hZ [font="Times]int i;
D!IY&H,wo [font="Times]boolean done = false;
wDe& 1(T^ [font="Times]i = 0;
;hN!s`vq [font="Times]for( ; !done; ) {
v
z '&%( [font="Times]System.out.println("i is " + i);
X_\otVh(D [font="Times]if(i == 10) done = true;
v,>Dbxn [font="Times]i++;
IB]l1< [font="Times]}
@r/nF5 [font="Times]}
]-/VHh [font="Times]}
循环语句的例子下载 @i IRmQ [font="Times] 2.分支语句[font="Times]
?+}_1x` [font="Times] if/else语句
a HR"n|7{ [font="Times]class IfElse {
vnZC,J ` [font="Times]public static void main(String args[]) {
9m~p0 ILh [font="Times]int month = 4; // April
YGCL2Y [font="Times]String season;
{[?(9u7R [font="Times]if(month == 12 || month == 1 || month == 2)
_.Uh)-yR [font="Times]season = "Winter";
Cd}<a?m, [font="Times]else if(month == 3 || month == 4 || month == 5)
mSh[}%swj [font="Times]season = "Spring";
5uj?#)N [font="Times]else if(month == 6 || month == 7 || month == 8)
6zuTQ^pz [font="Times]season = "Summer";
[%1CRk [font="Times]else if(month == 9 || month == 10 || month == 11)
Trz@~d/[,n [font="Times]season = "Autumn";
&(l9?EVq1 [font="Times]else
?QdWrE_
[font="Times]season = "Bogus Month";
%S^8c [font="Times]System.out.println("April is in the " + season + ".");
)cMh0SGcM1 [font="Times]}
\\B(r [font="Times]}
:emiQ [font="Times]//这段程序输出[font="Times]:
OU
$#5 [font="Times]//April is in the Spring.
_H7x9
y= [font="Times]// 注意[font="Times] “[font="Times]||”是或运算
q ,]L$ [font="Times] switch语句
>$/>#e~ [font="Times] class Switch {
fdi\hg^x [font="Times]public static void main(String args[]) {
gu.}M:u [font="Times]int month = 4;
O:{~urV [font="Times]String season;
!Pfr,a [font="Times]switch (month) {
x@;m8z0 [font="Times]case 12:
e)?
.r9pA; [font="Times]case 1:
}-2 2XYh [font="Times]case 2:
u[=r,^YQ [font="Times]season = "Winter";
q\4Xs$APq [font="Times]break;
TpwkD_fg [font="Times]case 3:
tGE$z]1c@ [font="Times]case 4:
b&N'C9/8 [font="Times]case 5:
LxSpctiNx [font="Times]season = "Spring";
x,pjpx [font="Times]break;
fW1CFRHH [font="Times]case 6:
J$w<$5UY [font="Times]case 7:
\aUC(K~o\; [font="Times]case 8:
_FU_Ubkr [font="Times]season = "Summer";
|a`Sc% [font="Times]break;
umH40rX+ [font="Times]case 9:
sW'AjI [font="Times]case 10:
Nv}=L
: E [font="Times]case 11:
BLf>_bUk [font="Times]season = "Autumn";
S3*`jF>q [font="Times]break;
/cQueUME` [font="Times]default:
+RM SA^ [font="Times]season = "Bogus Month";
jB Z&Ad@e [font="Times]}
}9# r0Vja [font="Times]System.out.println("April is in the " + season + ".");
_Gi4A [font="Times]}
H0gbSd+ [font="Times]}
分支语句代码下载 li'YDtMKCY J~zUp(>K [font="Times]switch语句适合于条件非常多的逻辑
;oKZ!ND 请看上述语句可以混合使用,请看
下载例子