全新java初学者实践教程6(Java SE5.0版)
^,$>z*WQ. 基本语法3
2bB&/Uumsd <~[A Q0}Sju+HX 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:
YMSA[hm wd/"! A4( [font="Times] 1.循环语句[font="Times]:while,do-while,for
5 GP,J,J h zh%ML3L [font="Times]2.分支语句[font="Times]:if-else,switch,
%:P&!F\? [font="Times]
d4h,
+OU 3.跳转语句[font="Times] break,continue,label: 和[font="Times]return
6uU2+I [font="Times]
TzCNY@y 4.异常处理语句[font="Times]:try-catch-finally,throw
m),3J4(q BAq@ H8*B 实践:
$YmD; [font="Times] 1.循环语句
>q:0w{.TU [font="Times] while 语句
RK*ZlD< [font="Times]class While {
dh~+0FZ{A [font="Times]public static void main(String args[]) {
<]u~;e57 [font="Times]int n = 10;
C>?`1d@ [font="Times]while(n > 0) {
c&Mci"nj0 [font="Times]System.out.println("tick " + n);
%Q}T9%Mtj [font="Times]n--;
{hr+ENgV [font="Times]}
Wa8?o~0"L [font="Times]}
@"6dq;" [font="Times]}
hY?x14m$3 [font="Times] do…while 语句
o+H;ZGT5H [font="Times] class DoWhile {
{ws:g![ [font="Times]public static void main(String args[]) {
"v"w ER? [font="Times]int n = 10;
483BrFV [font="Times]do {
\9*,[mvC [font="Times]System.out.println("tick " + n);
qw!_/Z3[ [font="Times]n--;
7,sslf2%K [font="Times]} while(n > 0);
FE)L? [font="Times]}
(5SN=6O [font="Times]}
G|Du/XYh 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。
*o/Q# [font="Times] for语句
0<{+M` G/ [font="Times] class ForTick {
]yxRaW9f [font="Times]public static void main(String args[]) {
`g;`yJX< [font="Times]int n;
H)s$0Xd
[font="Times]for(n=10; n>0; n--)
L
y!!+UM\ [font="Times]System.out.println("tick " + n);
8H>: C(h [font="Times]}
_pXy}D [font="Times]}
Z|FWQ8gZ4m 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。
8TK&i, 还有啊,[font="Times]for循环的部分可以为空的
u |hT1l [font="Times]class ForVar {
^_5Nh^ [font="Times]public static void main(String args[]) {
;_yp@.,\T [font="Times]int i;
l3sL!D1u [font="Times]boolean done = false;
-NG`mfu [font="Times]i = 0;
A.!V*1h{ [font="Times]for( ; !done; ) {
{%S>!RA [font="Times]System.out.println("i is " + i);
"g)@jqq:> [font="Times]if(i == 10) done = true;
p&nIUx" [font="Times]i++;
g,5r)FU` [font="Times]}
qL6Rs [font="Times]}
u0;FQr2 [font="Times]}
循环语句的例子下载 xZ*.@Pkr [font="Times] 2.分支语句[font="Times]
Y5}<7s\UDO [font="Times] if/else语句
( aGwe@AS [font="Times]class IfElse {
1!@KRV [font="Times]public static void main(String args[]) {
Zd/ACZ[ [font="Times]int month = 4; // April
;NrN#<j(! [font="Times]String season;
8+Y+\XZG [font="Times]if(month == 12 || month == 1 || month == 2)
.[v4'ww^ [font="Times]season = "Winter";
,8KD-" l^g [font="Times]else if(month == 3 || month == 4 || month == 5)
'V reO52 [font="Times]season = "Spring";
H!y%Fa Ti [font="Times]else if(month == 6 || month == 7 || month == 8)
zCdQI [font="Times]season = "Summer";
DK/xHIv8- [font="Times]else if(month == 9 || month == 10 || month == 11)
+H[GD! [font="Times]season = "Autumn";
s2*^ PG [font="Times]else
&ACM:&Ob [font="Times]season = "Bogus Month";
oC]|ARgQk| [font="Times]System.out.println("April is in the " + season + ".");
GW_@hYIqD [font="Times]}
:V>M{vd [font="Times]}
PYldqY [font="Times]//这段程序输出[font="Times]:
T@[(FVA N [font="Times]//April is in the Spring.
OY'490 [font="Times]// 注意[font="Times] “[font="Times]||”是或运算
sLE@Cm]k [font="Times] switch语句
\($EYhx [font="Times] class Switch {
J?\z{ ;qa [font="Times]public static void main(String args[]) {
x[Xj[O [font="Times]int month = 4;
b(lC7Xm [font="Times]String season;
|OXufV?I [font="Times]switch (month) {
?fB}9(6 [font="Times]case 12:
S7cxEOfAu [font="Times]case 1:
P
+U=/$o [font="Times]case 2:
26fbBt8nP [font="Times]season = "Winter";
r Bv [font="Times]break;
0hTv0#j# [font="Times]case 3:
>&K1+FSmyJ [font="Times]case 4:
x)M=_u2 _ [font="Times]case 5:
T{1Z(M+ [font="Times]season = "Spring";
i"}%ib*X [font="Times]break;
%KxL{HY [font="Times]case 6:
~/hyf] *j [font="Times]case 7:
M@e&uz!Rx [font="Times]case 8:
LQ5 WS [font="Times]season = "Summer";
k T$yHB # [font="Times]break;
Zy BN o] [font="Times]case 9:
rz c}2I [font="Times]case 10:
o#X|4bES [font="Times]case 11:
_ri1RK, [font="Times]season = "Autumn";
Is~bA_-
; [font="Times]break;
F&r+"O)^-R [font="Times]default:
J1I"H<}-6 [font="Times]season = "Bogus Month";
8iTX}$t\{ [font="Times]}
d($f8{~W [font="Times]System.out.println("April is in the " + season + ".");
;<Dou7= [font="Times]}
VXforI [font="Times]}
分支语句代码下载 rs$sAa*f )NeI]p [font="Times]switch语句适合于条件非常多的逻辑
VmLV:"P}^ 请看上述语句可以混合使用,请看
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