全新java初学者实践教程6(Java SE5.0版)
S$ffTdRz 基本语法3
m!5Edo-;< u}b%-:- gxx#<=` 我们这个教程侧重的是实践的内容和语言的重点。在[font="Times]java语言中还有很多细节的东西,请参考[font="Times]sun公司的官方培训教程。我们这里不能一一讲述。这节课我们来给大家提供一些程序流程控制的一些例子供大家学习。计算机怎么做事情,是我们教给他的。我们用它解决实际生活中的问题,所以计算机要描述现实生活中的流程。[font="Times]Java语言中提供了[font="Times]4类程序控制语句,来描述流程:
,Qs%bq{t E>+>!On)b [font="Times] 1.循环语句[font="Times]:while,do-while,for
yzT4D>1, XBoq/kbw! [font="Times]2.分支语句[font="Times]:if-else,switch,
|az2vD6P [font="Times]
)k;;O7Ck 3.跳转语句[font="Times] break,continue,label: 和[font="Times]return
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BQs 4.异常处理语句[font="Times]:try-catch-finally,throw
l dqU#{ pH3<QNq5 实践:
PMUW<UI [font="Times] 1.循环语句
*YSRZvD<\ [font="Times] while 语句
|nE4tN#J< [font="Times]class While {
/3&MUB*z&y [font="Times]public static void main(String args[]) {
0` .5gxm [font="Times]int n = 10;
L0oVXmlr [font="Times]while(n > 0) {
|Ve,Y [font="Times]System.out.println("tick " + n);
VD<z]@ [font="Times]n--;
2vWn(6` [font="Times]}
Q8MIpa!: [font="Times]}
7Ja*T@ ! h [font="Times]}
;tSAQ [font="Times] do…while 语句
j+@3.^vK [font="Times] class DoWhile {
AJm$(3?/D [font="Times]public static void main(String args[]) {
tv26eK
38 [font="Times]int n = 10;
,J8n}7aI [font="Times]do {
^qnmKA>"F [font="Times]System.out.println("tick " + n);
m7DKC, [font="Times]n--;
"Kdn`zN{ [font="Times]} while(n > 0);
G;$;$gM [font="Times]}
'qvj[lpGr [font="Times]}
K|YB)y 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。
aCI3Tx&2qT [font="Times] for语句
K{{_qFj@<y [font="Times] class ForTick {
zCuB+r=C [font="Times]public static void main(String args[]) {
`CI_zc=jx [font="Times]int n;
2;u
i'B [font="Times]for(n=10; n>0; n--)
GX0zirz [font="Times]System.out.println("tick " + n);
ZP5 !O[Ut [font="Times]}
#=={h?UDT [font="Times]}
9h?'zyX
B 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。
r*]pL< 还有啊,[font="Times]for循环的部分可以为空的
Rq%Kw> {& [font="Times]class ForVar {
1"L"LU' [font="Times]public static void main(String args[]) {
r5Tdp)S [font="Times]int i;
<l$ d>, [font="Times]boolean done = false;
P.qzP/Ny [font="Times]i = 0;
Id##367R [font="Times]for( ; !done; ) {
4A6Yl6\Y [font="Times]System.out.println("i is " + i);
@1Q-.54a [font="Times]if(i == 10) done = true;
uINdeq 7|F [font="Times]i++;
|PlNVd2 [font="Times]}
uO`MA%
z< [font="Times]}
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循环语句的例子下载 u;gO+)wqv [font="Times] 2.分支语句[font="Times]
qQi\/~Y[: [font="Times] if/else语句
z8'1R6nq [font="Times]class IfElse {
3_~iq>l [font="Times]public static void main(String args[]) {
Ph1XI&us9 [font="Times]int month = 4; // April
yjg&/6 [font="Times]String season;
^w.hI5ua) [font="Times]if(month == 12 || month == 1 || month == 2)
C=/B\G/.9 [font="Times]season = "Winter";
r~lZ8$KC [font="Times]else if(month == 3 || month == 4 || month == 5)
8s@N NjV [font="Times]season = "Spring";
E5d$n*A [font="Times]else if(month == 6 || month == 7 || month == 8)
iU;e!\A [font="Times]season = "Summer";
UnF8#~ [font="Times]else if(month == 9 || month == 10 || month == 11)
(
%\7dxiK [font="Times]season = "Autumn";
.mt%8GM [font="Times]else
BzP,Tu{, [font="Times]season = "Bogus Month";
~0a5 [font="Times]System.out.println("April is in the " + season + ".");
FT@uZWgQ= [font="Times]}
)rD!4"8/A [font="Times]}
[d6! [font="Times]//这段程序输出[font="Times]:
D j&~x
[font="Times]//April is in the Spring.
_*fNa!@hY [font="Times]// 注意[font="Times] “[font="Times]||”是或运算
&0Yg:{k$ [font="Times] switch语句
Ki\.w~Qs [font="Times] class Switch {
8Ojqm#/f [font="Times]public static void main(String args[]) {
K>@yk9)vi [font="Times]int month = 4;
.B#
.
[font="Times]String season;
!Qe;oMqy} [font="Times]switch (month) {
aa`(2%(: [font="Times]case 12:
ej`%}e%2 [font="Times]case 1:
MC}t8L= [font="Times]case 2:
XH"+oW [font="Times]season = "Winter";
/x6p [font="Times]break;
a /sj W [font="Times]case 3:
`hi=y BO [font="Times]case 4:
<+i(CGw [font="Times]case 5:
$zMshLT [font="Times]season = "Spring";
mll:rWC) [font="Times]break;
2J ZR"P [font="Times]case 6:
&X$T "Dp [font="Times]case 7:
=_7wd*, [font="Times]case 8:
$*fJKR_N [font="Times]season = "Summer";
Ae+)RBpc [font="Times]break;
/o9T [^\ [font="Times]case 9:
,^UqE{ [font="Times]case 10:
;*<tU
n^t [font="Times]case 11:
u0q$`9J [font="Times]season = "Autumn";
4wl1hp>, [font="Times]break;
/\I6j;$z [font="Times]default:
;]>kp^C# [font="Times]season = "Bogus Month";
E-bswUVaEE [font="Times]}
z)qYW6o% [font="Times]System.out.println("April is in the " + season + ".");
tS'lJu [font="Times]}
/ (&E [font="Times]}
分支语句代码下载 Fb5U@X/vE Gk,Bx1y [font="Times]switch语句适合于条件非常多的逻辑
E.oJ[; 请看上述语句可以混合使用,请看
下载例子