全新java初学者实践教程6(Java SE5.0版)
R=~+- ^O! 基本语法3
"gXz{$q /i|T \ R_ojK&% 我们这个教程侧重的是实践的内容和语言的重点。在[font="Times]java语言中还有很多细节的东西,请参考[font="Times]sun公司的官方培训教程。我们这里不能一一讲述。这节课我们来给大家提供一些程序流程控制的一些例子供大家学习。计算机怎么做事情,是我们教给他的。我们用它解决实际生活中的问题,所以计算机要描述现实生活中的流程。[font="Times]Java语言中提供了[font="Times]4类程序控制语句,来描述流程:
:\1:n ~qm<~T_0 [font="Times] 1.循环语句[font="Times]:while,do-while,for
yzt6 xt@zP)6G [font="Times]2.分支语句[font="Times]:if-else,switch,
Q>u$tLX& [font="Times]
+rbj%v}Fh 3.跳转语句[font="Times] break,continue,label: 和[font="Times]return
K'~wlO@O [font="Times]
_>B0q|]j4' 4.异常处理语句[font="Times]:try-catch-finally,throw
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: 实践:
uYAPGs#k [font="Times] 1.循环语句
O:3pp8 [font="Times] while 语句
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bb:)> [font="Times]class While {
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A)H<Zt [font="Times]public static void main(String args[]) {
[>+(zlK" [font="Times]int n = 10;
Q+E%"`3V4l [font="Times]while(n > 0) {
T<06y3sN [font="Times]System.out.println("tick " + n);
'/kSUvd [font="Times]n--;
>(Jy=m? [font="Times]}
wxpE5v+f| [font="Times]}
IC>OxYg* [font="Times]}
k.>*!l0 [font="Times] do…while 语句
`6`NuZ*6g [font="Times] class DoWhile {
~?8B~l^ [font="Times]public static void main(String args[]) {
Q@hx+aM [font="Times]int n = 10;
#P$=P2o [font="Times]do {
a9qB8/Gg[ [font="Times]System.out.println("tick " + n);
E^ _P [font="Times]n--;
x]lv:m\)jT [font="Times]} while(n > 0);
w1EYXe [font="Times]}
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$:w4_X5T 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。
S/& _ [font="Times] for语句
0f/=C9L [font="Times] class ForTick {
,/{mRw% [font="Times]public static void main(String args[]) {
"0Uh(9Fv [font="Times]int n;
sY!PXD0Q [font="Times]for(n=10; n>0; n--)
)Ac+5bs [font="Times]System.out.println("tick " + n);
x(h(a#,r [font="Times]}
D+d\<": [font="Times]}
+Ck F#H ~ 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。
Qfr%BQV 还有啊,[font="Times]for循环的部分可以为空的
hN$6Kx>{ [font="Times]class ForVar {
Mh>H5l.1i [font="Times]public static void main(String args[]) {
ufm`h)N [font="Times]int i;
.P.TqT@)r [font="Times]boolean done = false;
_|rrl [font="Times]i = 0;
7yxZe4~|# [font="Times]for( ; !done; ) {
u&1n~t` [font="Times]System.out.println("i is " + i);
)e|Cd} 2 [font="Times]if(i == 10) done = true;
:\x53-&hO4 [font="Times]i++;
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[font="Times]}
Ath^UKO" [font="Times]}
gUzCDB^.: [font="Times]}
循环语句的例子下载 qlmz@kTb [font="Times] 2.分支语句[font="Times]
iD#HBo [font="Times] if/else语句
J6/Mm7R [font="Times]class IfElse {
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[font="Times]public static void main(String args[]) {
@$z/=g sy [font="Times]int month = 4; // April
v;AMx-_WH [font="Times]String season;
S',i [font="Times]if(month == 12 || month == 1 || month == 2)
kxp$Nnk [font="Times]season = "Winter";
{X<mr~ [font="Times]else if(month == 3 || month == 4 || month == 5)
7F.t>$' [font="Times]season = "Spring";
U8kH'OD [font="Times]else if(month == 6 || month == 7 || month == 8)
_ In[Z?P} [font="Times]season = "Summer";
6?Ul)' [font="Times]else if(month == 9 || month == 10 || month == 11)
*`[dC,+`. [font="Times]season = "Autumn";
Px5ArSS [font="Times]else
My0h9'K [font="Times]season = "Bogus Month";
u{xjFx- [font="Times]System.out.println("April is in the " + season + ".");
@kC>+4s! [font="Times]}
>K**SjVG [font="Times]}
iX qB-4" [font="Times]//这段程序输出[font="Times]:
fRC(Yyx [font="Times]//April is in the Spring.
gsd9QW [font="Times]// 注意[font="Times] “[font="Times]||”是或运算
aQ mgDF [font="Times] switch语句
>lQ&^9EI% [font="Times] class Switch {
&-W5T?Sl [font="Times]public static void main(String args[]) {
|2(z<b&y= [font="Times]int month = 4;
4Waot [font="Times]String season;
z.n`0`^ [font="Times]switch (month) {
% Uybp [font="Times]case 12:
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