全新java初学者实践教程6(Java SE5.0版)
,*y\b|<j 基本语法3
676r0` vlygS(Y_7 X9|={ng)g# 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:
+,"O#`sy< S:.Vt&+NJ [font="Times] 1.循环语句[font="Times]:while,do-while,for
<)f1skJsP -&AgjzN! [font="Times]2.分支语句[font="Times]:if-else,switch,
12D>~#J [font="Times]
hd~3I4D 3.跳转语句[font="Times] break,continue,label: 和[font="Times]return
u$vA9g4 [font="Times]
4[&L<D6h 4.异常处理语句[font="Times]:try-catch-finally,throw
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j<A vpnOc2 - 实践:
+7`7cOqXg [font="Times] 1.循环语句
'@jP$6T& [font="Times] while 语句
D-v}@tS' [font="Times]class While {
jcC"SqL [font="Times]public static void main(String args[]) {
uR;m<wPH,f [font="Times]int n = 10;
d*M:PjG@ [font="Times]while(n > 0) {
C(4r>TNm [font="Times]System.out.println("tick " + n);
VL[} [font="Times]n--;
Wu{cE;t [font="Times]}
vs*Q { [font="Times]}
n7CwGN% [font="Times]}
lhp.zl [font="Times] do…while 语句
^V5VRGq [font="Times] class DoWhile {
[]\=(Uc; [font="Times]public static void main(String args[]) {
dKG 2f [font="Times]int n = 10;
lRy^Wp [font="Times]do {
qHU=X"rn [font="Times]System.out.println("tick " + n);
4!l%@R>O2 [font="Times]n--;
2@W'q=+0 [font="Times]} while(n > 0);
2.
t'!uwI [font="Times]}
)2&U
Rt. [font="Times]}
['`Vg=O.{ 二者区别,[font="Times]do…while至少循环一次,而[font="Times]while的表达式要是为[font="Times]flase的话可以一次也不循环。再通俗一点,[font="Times]do…while就算是括号里的是[font="Times]flase,人家最少也能[font="Times]do一次。
h'wI [font="Times] for语句
JBvMe H5 [font="Times] class ForTick {
qm!&(8NfK [font="Times]public static void main(String args[]) {
?y1G,0, [font="Times]int n;
dTATJ)NH [font="Times]for(n=10; n>0; n--)
p+ki1!Ed [font="Times]System.out.println("tick " + n);
.huk>
[font="Times]}
@xqjAcfg [font="Times]}
a7Xa3 vlpO 与上面那两个的区别,[font="Times]for循环执行的次数是可以在执行之前确定的。通俗一点说吧,看这个例子[font="Times] for(n=10; n>0; n--)就是在括号里的时候,就已经知道要循环[font="Times]10次了。
(**k4c, 还有啊,[font="Times]for循环的部分可以为空的
H
N )@sLPc [font="Times]class ForVar {
eHIsTL@Fp [font="Times]public static void main(String args[]) {
<k c9KE [font="Times]int i;
+nOa&d\ [font="Times]boolean done = false;
t,v=~LE [font="Times]i = 0;
x%$as; [font="Times]for( ; !done; ) {
s)eU^4m [font="Times]System.out.println("i is " + i);
E
U#
M. [font="Times]if(i == 10) done = true;
z:Q4E|IX [font="Times]i++;
$-J=UT2m [font="Times]}
oh@|*RU [font="Times]}
#mFY?Zp) [font="Times]}
循环语句的例子下载 YXFUZ9a#e [font="Times] 2.分支语句[font="Times]
axpn*(yE [font="Times] if/else语句
/XeCJxo8 [font="Times]class IfElse {
ws_/F [font="Times]public static void main(String args[]) {
FN>ns, [font="Times]int month = 4; // April
usFhcU [font="Times]String season;
2Nau]y]= [font="Times]if(month == 12 || month == 1 || month == 2)
ywCF{rRd [font="Times]season = "Winter";
LQr+)wI [font="Times]else if(month == 3 || month == 4 || month == 5)
fRow@DI\ [font="Times]season = "Spring";
i& phko} [font="Times]else if(month == 6 || month == 7 || month == 8)
*~b}]M700 [font="Times]season = "Summer";
xnp5XhU [font="Times]else if(month == 9 || month == 10 || month == 11)
kX1#+X [font="Times]season = "Autumn";
"m'roU [font="Times]else
&%infPI' [font="Times]season = "Bogus Month";
sf(2~BMQI [font="Times]System.out.println("April is in the " + season + ".");
U6sPJc< [font="Times]}
bS2)L4MQY [font="Times]}
`#Yv(a2TY [font="Times]//这段程序输出[font="Times]:
V=+wsc [font="Times]//April is in the Spring.
=D}]|ie [font="Times]// 注意[font="Times] “[font="Times]||”是或运算
(&=gM [font="Times] switch语句
o4l=oY:' [font="Times] class Switch {
|PY*"Ul [font="Times]public static void main(String args[]) {
V']{n7a- [font="Times]int month = 4;
Y \oz9tf8 [font="Times]String season;
e5HHsR6 [font="Times]switch (month) {
920 o]Dh=t [font="Times]case 12:
{i!@C(M3 [font="Times]case 1:
gA/8Df\G:l [font="Times]case 2:
xUw)mUn@N [font="Times]season = "Winter";
-Y:^<C^^&8 [font="Times]break;
{CVn&|}J [font="Times]case 3:
Zf [#~4 [font="Times]case 4:
H\[:uUK5\ [font="Times]case 5:
^j)0&}fB [font="Times]season = "Spring";
Gd:fh5u': [font="Times]break;
B}|(/a@* [font="Times]case 6:
$,&3:ke1 [font="Times]case 7:
nN|1cJ'.Fk [font="Times]case 8:
<aVfgVS [font="Times]season = "Summer";
P+/6-C J [font="Times]break;
)=EJFQ*v [font="Times]case 9:
'{I YANVT [font="Times]case 10:
5m(V(@a3 [font="Times]case 11:
fcLVE [font="Times]season = "Autumn";
#1#?k [font="Times]break;
p> #QFd"m [font="Times]default:
o$[alh;c+W [font="Times]season = "Bogus Month";
t(sQw '> [font="Times]}
'_`O&rbT [font="Times]System.out.println("April is in the " + season + ".");
;H%T5$:trP [font="Times]}
z~ R: !O- [font="Times]}
分支语句代码下载 :Dn{ {Bd 0 [font="Times]switch语句适合于条件非常多的逻辑
0DIXd*oj & 请看上述语句可以混合使用,请看
下载例子