全新java初学者实践教程6(Java SE5.0版)
d0-}Xl 基本语法3
&}T`[ d_Z |lJXI:GG 2#+@bk>^{ 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:
$ya#-pi`; ;uoH+`pf [font="Times] 1.循环语句[font="Times]:while,do-while,for
Tr@`ozp8 ev8E.ehD [font="Times]2.分支语句[font="Times]:if-else,switch,
~ S-x-cZ [font="Times]
6Ir
?@O1'! 3.跳转语句[font="Times] break,continue,label: 和[font="Times]return
+e?ixvld [font="Times]
*EV] 8 4.异常处理语句[font="Times]:try-catch-finally,throw
).tZMLM/- m7M*)N8 实践:
+ !_^MB kk [font="Times] 1.循环语句
#mllVQ [font="Times] while 语句
f2{4Y) [font="Times]class While {
0.@/I}R[ [font="Times]public static void main(String args[]) {
~Zj?%4 [font="Times]int n = 10;
Wb4sfP_ [font="Times]while(n > 0) {
MH !CzV& [font="Times]System.out.println("tick " + n);
l>=c] [font="Times]n--;
ie$=3nZJ} [font="Times]}
/au\OBUge [font="Times]}
Qy6Avw/$ [font="Times]}
k*-+@U"+ [font="Times] do…while 语句
8tdUnh%/ [font="Times] class DoWhile {
N}dJ)<(2~ [font="Times]public static void main(String args[]) {
8AefgjE [font="Times]int n = 10;
*K+*0_ [font="Times]do {
c89RuI `B~ [font="Times]System.out.println("tick " + n);
gsU&}R1*h [font="Times]n--;
x(t}H8q [font="Times]} while(n > 0);
zM@iG]?kc [font="Times]}
!4 hs9b [font="Times]}
,$}Q#q 二者区别,[font="Times]do…while至少循环一次,而[font="Times]while的表达式要是为[font="Times]flase的话可以一次也不循环。再通俗一点,[font="Times]do…while就算是括号里的是[font="Times]flase,人家最少也能[font="Times]do一次。
ho(Y?'^t3 [font="Times] for语句
.
}=;]= [font="Times] class ForTick {
Jhj]rsGk [font="Times]public static void main(String args[]) {
)E4COw+ [font="Times]int n;
Wc]Fg9E [font="Times]for(n=10; n>0; n--)
3[e@mcO [font="Times]System.out.println("tick " + n);
{ j/w3 [font="Times]}
?&X6VNbU [font="Times]}
#JW1JCT
与上面那两个的区别,[font="Times]for循环执行的次数是可以在执行之前确定的。通俗一点说吧,看这个例子[font="Times] for(n=10; n>0; n--)就是在括号里的时候,就已经知道要循环[font="Times]10次了。
z?gJHN< 还有啊,[font="Times]for循环的部分可以为空的
bX6*/N [font="Times]class ForVar {
T4f:0r;^f* [font="Times]public static void main(String args[]) {
v$mA7|(t! [font="Times]int i;
Hv`Zc* [font="Times]boolean done = false;
FCP5EN [font="Times]i = 0;
8WyG49eic [font="Times]for( ; !done; ) {
P,%|(qB [font="Times]System.out.println("i is " + i);
nut7b [font="Times]if(i == 10) done = true;
h5Z\9`f[ [font="Times]i++;
@+2Zt% [font="Times]}
UG!&n@R [font="Times]}
.K93VTzy [font="Times]}
循环语句的例子下载 jG^~{7# [font="Times] 2.分支语句[font="Times]
{Ise (>V [font="Times] if/else语句
Q3KBG8 [font="Times]class IfElse {
C9nNziws [font="Times]public static void main(String args[]) {
rcbixOT [font="Times]int month = 4; // April
`C()H@; [font="Times]String season;
P9'5=e@jB [font="Times]if(month == 12 || month == 1 || month == 2)
;zOZu~Q|' [font="Times]season = "Winter";
3gM{lS}h# [font="Times]else if(month == 3 || month == 4 || month == 5)
nph{ [font="Times]season = "Spring";
_9-Ajv [font="Times]else if(month == 6 || month == 7 || month == 8)
AH}
nTm [font="Times]season = "Summer";
!uZ+r% [font="Times]else if(month == 9 || month == 10 || month == 11)
@2u<Bh}} [font="Times]season = "Autumn";
980+Y [font="Times]else
U-k;kmaj [font="Times]season = "Bogus Month";
|-R::gm [font="Times]System.out.println("April is in the " + season + ".");
,S8Vfb & [font="Times]}
eJwr [font="Times]}
*dQRs6 [font="Times]//这段程序输出[font="Times]:
yjpjJ [font="Times]//April is in the Spring.
oO|^ [b# [font="Times]// 注意[font="Times] “[font="Times]||”是或运算
FFkG,XH [font="Times] switch语句
:vr,@1c [font="Times] class Switch {
f^]AyU;F: [font="Times]public static void main(String args[]) {
U!'lc}5 [font="Times]int month = 4;
>hhd9 [font="Times]String season;
<V,?!}V [font="Times]switch (month) {
2iGRw4`_a [font="Times]case 12:
_5)#{o< [font="Times]case 1:
01dx}L@hz [font="Times]case 2:
}/LYI [font="Times]season = "Winter";
vW_A.iI"e [font="Times]break;
YOY+z\Q [font="Times]case 3:
m^=,
RfUUd [font="Times]case 4:
NqWHR~& [font="Times]case 5:
w(yU\
N [font="Times]season = "Spring";
`%=Jsi0.Nq [font="Times]break;
wv7jh~x(4 [font="Times]case 6:
D;L :a`Y [font="Times]case 7:
cU>&E*wD [font="Times]case 8:
H )}WWXK [font="Times]season = "Summer";
<Hp"ZCN [font="Times]break;
y((_V%F} [font="Times]case 9:
y"hM6JI [font="Times]case 10:
rEf\|x=st: [font="Times]case 11:
<\8 [font="Times]season = "Autumn";
t2:c@) [font="Times]break;
Pjy?&;GvT [font="Times]default:
sHuz10 [font="Times]season = "Bogus Month";
RmQt%a7\{ [font="Times]}
L7g&]% [font="Times]System.out.println("April is in the " + season + ".");
$O>@(K [font="Times]}
oL@ou{iQ [font="Times]}
分支语句代码下载 10rGA=x'( :2My|3H\ [font="Times]switch语句适合于条件非常多的逻辑
&>jkfG 请看上述语句可以混合使用,请看
下载例子