全新java初学者实践教程6(Java SE5.0版)
3tS~:6-/ 基本语法3
JC;^--0(z f^<6`Aeq *JCQu0 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:
^c:Fy+fb Y"OG@1V;8 [font="Times] 1.循环语句[font="Times]:while,do-while,for
nqwAQhzy( asY[8r?U [font="Times]2.分支语句[font="Times]:if-else,switch,
oB74y [font="Times]
It2" x; 3.跳转语句[font="Times] break,continue,label: 和[font="Times]return
el:9 wq [font="Times]
4C}bJzZ 4.异常处理语句[font="Times]:try-catch-finally,throw
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5& 实践:
fN'HE#W1Xa [font="Times] 1.循环语句
Vp>|hj po [font="Times] while 语句
QWMdn [font="Times]class While {
2tal [font="Times]public static void main(String args[]) {
ox+ 3U [font="Times]int n = 10;
$.9{if#o& [font="Times]while(n > 0) {
|&Ym@Jyj [font="Times]System.out.println("tick " + n);
P-ri=E}> [font="Times]n--;
SM`w;?L:? [font="Times]}
h6} lpd [font="Times]}
LBF 1;zjK [font="Times]}
F<!)4>2@ [font="Times] do…while 语句
765p/** [font="Times] class DoWhile {
q$aaA`E% [font="Times]public static void main(String args[]) {
~ o1x;Y6 [font="Times]int n = 10;
B" 3dQwQ [font="Times]do {
|=&cQRY!p [font="Times]System.out.println("tick " + n);
-WYAN:s [font="Times]n--;
26xXl|I [font="Times]} while(n > 0);
_x!7}O#k [font="Times]}
uL[.ND2._& [font="Times]}
}d<}FJ-, 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。
<Qxh)@
N [font="Times] for语句
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H6c{'& [font="Times] class ForTick {
hGiz)v~ [font="Times]public static void main(String args[]) {
I_A@BnM{I [font="Times]int n;
-&<Whhs.@ [font="Times]for(n=10; n>0; n--)
8=]Tr3 [font="Times]System.out.println("tick " + n);
'Y]mOD^p [font="Times]}
ij? [font="Times]}
4q<=K= F 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。
y~75r\"R 还有啊,[font="Times]for循环的部分可以为空的
`3:.??7N [font="Times]class ForVar {
Dgy]ae(Hb3 [font="Times]public static void main(String args[]) {
4Z/f@ZD [font="Times]int i;
L(U"U#QZ [font="Times]boolean done = false;
3;a<_cE*@ [font="Times]i = 0;
yrR1[aT [font="Times]for( ; !done; ) {
zToq^T [font="Times]System.out.println("i is " + i);
8O Soel [font="Times]if(i == 10) done = true;
p ZZc:\fJ [font="Times]i++;
s M +WkN}{ [font="Times]}
z@w Mc
EH [font="Times]}
$]8h $ [font="Times]}
循环语句的例子下载 Qci4J [font="Times] 2.分支语句[font="Times]
V
=-WYu [font="Times] if/else语句
rta:f800z [font="Times]class IfElse {
'{(UW.Awo [font="Times]public static void main(String args[]) {
u?+Kkkk [font="Times]int month = 4; // April
kV38`s>+ [font="Times]String season;
KG=h& [font="Times]if(month == 12 || month == 1 || month == 2)
?2oHZ%G [font="Times]season = "Winter";
Ry|!pV [font="Times]else if(month == 3 || month == 4 || month == 5)
$H-!j%hV [font="Times]season = "Spring";
f-%NaTI [font="Times]else if(month == 6 || month == 7 || month == 8)
W16,Alf: [font="Times]season = "Summer";
C?2'+K [font="Times]else if(month == 9 || month == 10 || month == 11)
G8;w{-{m [font="Times]season = "Autumn";
*f?4
[font="Times]else
YJo["Q [font="Times]season = "Bogus Month";
KhMSL [font="Times]System.out.println("April is in the " + season + ".");
=J ym%m [font="Times]}
[h,Q Bz [font="Times]}
L>YU,I\o [font="Times]//这段程序输出[font="Times]:
-UD\;D?$ [font="Times]//April is in the Spring.
[B|MlrZ
[font="Times]// 注意[font="Times] “[font="Times]||”是或运算
3:C oZ [font="Times] switch语句
q5#J~n8Wr [font="Times] class Switch {
K=,F#kn [font="Times]public static void main(String args[]) {
c.j$9=XLBG [font="Times]int month = 4;
]Ei0d8Uo [font="Times]String season;
>>5NX"{ [font="Times]switch (month) {
(e[}/hf6 [font="Times]case 12:
>2Kh0rIH [font="Times]case 1:
|P%DkM*X [font="Times]case 2:
1[yq0^\]M[ [font="Times]season = "Winter";
TqddOp [font="Times]break;
E8~}PQW:I [font="Times]case 3:
?G-e](]^< [font="Times]case 4:
2^l[(N [font="Times]case 5:
oDU ;E [font="Times]season = "Spring";
48*Do}l] [font="Times]break;
EeF'&zE- [font="Times]case 6:
t>[KVVg
W [font="Times]case 7:
rhb@FE)Mc [font="Times]case 8:
<0PT"ij [font="Times]season = "Summer";
q@xBJ[IM [font="Times]break;
f?'JAC* [font="Times]case 9:
NvvUSyk\;s [font="Times]case 10:
()3O=! [font="Times]case 11:
L_K=g_] [font="Times]season = "Autumn";
|K|h+fgG6* [font="Times]break;
y})70w@+_ [font="Times]default:
cJL'$`gWf [font="Times]season = "Bogus Month";
,qYJioWX [font="Times]}
hc'-Dh [font="Times]System.out.println("April is in the " + season + ".");
x4/M}%h!;B [font="Times]}
J|w)&bV [font="Times]}
分支语句代码下载 mI>,.&eo 44F`$.v96 [font="Times]switch语句适合于条件非常多的逻辑
[Ts"OPb%~ 请看上述语句可以混合使用,请看
下载例子