全新java初学者实践教程6(Java SE5.0版)
YXlaE=9bn 基本语法3
B<Zm'hdX 2{6%+>jB 8
U<$u,WS 我们这个教程侧重的是实践的内容和语言的重点。在[font="Times]java语言中还有很多细节的东西,请参考[font="Times]sun公司的官方培训教程。我们这里不能一一讲述。这节课我们来给大家提供一些程序流程控制的一些例子供大家学习。计算机怎么做事情,是我们教给他的。我们用它解决实际生活中的问题,所以计算机要描述现实生活中的流程。[font="Times]Java语言中提供了[font="Times]4类程序控制语句,来描述流程:
\dHdL\f sJ>JHv [font="Times] 1.循环语句[font="Times]:while,do-while,for
=mp"=% 6N#0D2~^ [font="Times]2.分支语句[font="Times]:if-else,switch,
?^by3\,VZ [font="Times]
%_L~"E 2e 3.跳转语句[font="Times] break,continue,label: 和[font="Times]return
O'~>AC5{ [font="Times]
INRP@Cp1 4.异常处理语句[font="Times]:try-catch-finally,throw
PiVp(; rtQ 8+n*S$ 实践:
wqasI@vyu [font="Times] 1.循环语句
&-c{ [font="Times] while 语句
ev[!:*6P [font="Times]class While {
mb?r{WCi [font="Times]public static void main(String args[]) {
`gSJEq [font="Times]int n = 10;
[sXnB$ [font="Times]while(n > 0) {
UfNcI[xr [font="Times]System.out.println("tick " + n);
r}4 [font="Times]n--;
KX^! t3l6 [font="Times]}
t!&p5wJ*Q [font="Times]}
aJzyEb [font="Times]}
n_/;j$h [font="Times] do…while 语句
5{|tE! [font="Times] class DoWhile {
-%_v b6u [font="Times]public static void main(String args[]) {
.P(Ax:g [font="Times]int n = 10;
-\[&<o@/D [font="Times]do {
hcT5> w[ [font="Times]System.out.println("tick " + n);
?~9o2[ [font="Times]n--;
?58*#'r [font="Times]} while(n > 0);
6
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<Em|0hth 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。
b^'>XT~1J& [font="Times] for语句
5@nvcCp [font="Times] class ForTick {
.)|2^ 'W [font="Times]public static void main(String args[]) {
!F08F>@D [font="Times]int n;
l,k.Jo5 [font="Times]for(n=10; n>0; n--)
wu;^fL [font="Times]System.out.println("tick " + n);
M!b-;{;' [font="Times]}
87-z=>IU [font="Times]}
] ]lN[J 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。
Ro.br:'Bw 还有啊,[font="Times]for循环的部分可以为空的
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V [font="Times]class ForVar {
}Ryrd!3bY [font="Times]public static void main(String args[]) {
[l*;+N+ [font="Times]int i;
Ewa/6=]LA [font="Times]boolean done = false;
(r-8*)Qh8 [font="Times]i = 0;
LJwy,- [font="Times]for( ; !done; ) {
?2<V./2F [font="Times]System.out.println("i is " + i);
D}/nE>* [font="Times]if(i == 10) done = true;
CTf39R|7_ [font="Times]i++;
G7YBo4v [font="Times]}
4CK$W`V [font="Times]}
A,;[9J2\& [font="Times]}
循环语句的例子下载 av>Ff6w)Y [font="Times] 2.分支语句[font="Times]
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[font="Times] if/else语句
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[font="Times]class IfElse {
ja%IGaH;s [font="Times]public static void main(String args[]) {
l:14uWu| [font="Times]int month = 4; // April
eEX* \1Gg [font="Times]String season;
D"<>!]@(a [font="Times]if(month == 12 || month == 1 || month == 2)
(L,>P`CR6 [font="Times]season = "Winter";
-cB>; f)5r [font="Times]else if(month == 3 || month == 4 || month == 5)
]owcx=5q%' [font="Times]season = "Spring";
V?r(; x [font="Times]else if(month == 6 || month == 7 || month == 8)
t&MLgu [font="Times]season = "Summer";
suFO~/lRno [font="Times]else if(month == 9 || month == 10 || month == 11)
Ih%LKFT [font="Times]season = "Autumn";
,H@ x. [font="Times]else
p&lT! 5P!A [font="Times]season = "Bogus Month";
PcEE@W9 [font="Times]System.out.println("April is in the " + season + ".");
jP )VTk_ [font="Times]}
;tWi4iT+. [font="Times]}
_53NuEM1 [font="Times]//这段程序输出[font="Times]:
K[[ 5H [font="Times]//April is in the Spring.
wF)g@cw [font="Times]// 注意[font="Times] “[font="Times]||”是或运算
t/c)[l hV [font="Times] switch语句
xP5Z -eL [font="Times] class Switch {
n7,LfO# [font="Times]public static void main(String args[]) {
J8@7
5p9 [font="Times]int month = 4;
`e}6/~R` [font="Times]String season;
RX,c 4; [font="Times]switch (month) {
&&TAX [font="Times]case 12:
xeKfc}:&z [font="Times]case 1:
g)=-%n'RoE [font="Times]case 2:
BUU ) Sz [font="Times]season = "Winter";
#F:\_!2c [font="Times]break;
4=ZN4=(_[ [font="Times]case 3:
hEfFMi=a` [font="Times]case 4:
Z#flu Q%V [font="Times]case 5:
ngl8) B [font="Times]season = "Spring";
T-.Bof(?w [font="Times]break;
jWGX:XB [font="Times]case 6:
wQrD(Dv(yA [font="Times]case 7:
wyUfmk_} [font="Times]case 8:
AxiCpAS;J [font="Times]season = "Summer";
^03M~SNCj [font="Times]break;
RO8]R2A [font="Times]case 9:
;s w3MRJ [font="Times]case 10:
fK5iOj'Q [font="Times]case 11:
Rqun}v} [font="Times]season = "Autumn";
ke5_lr( [font="Times]break;
;f~z_3g [font="Times]default:
&h?8yV4B [font="Times]season = "Bogus Month";
Dlx-mm_ [font="Times]}
$m0-IyXcv [font="Times]System.out.println("April is in the " + season + ".");
ntD8:%m [font="Times]}
sXR}#*8p
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分支语句代码下载 G~19Vv*; eS; W>d [font="Times]switch语句适合于条件非常多的逻辑
giu8EjzK 请看上述语句可以混合使用,请看
下载例子