全新java初学者实践教程6(Java SE5.0版)
E gal4 基本语法3
QzzW x2 "9^j. "E8zh|m o 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:
00SbH$SU 1}:bqI.<W [font="Times] 1.循环语句[font="Times]:while,do-while,for
_:-ha?W$;y =}v}my3y" [font="Times]2.分支语句[font="Times]:if-else,switch,
%T)oCjM[\ [font="Times]
kWe{r5C7 3.跳转语句[font="Times] break,continue,label: 和[font="Times]return
}2uI?i8 [font="Times]
hvuIxqv !y 4.异常处理语句[font="Times]:try-catch-finally,throw
y7$iOR `KK>~T_$J 实践:
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[font="Times] 1.循环语句
y6IXd W [font="Times] while 语句
g|<]B$yN# [font="Times]class While {
-x'z
XvWZ [font="Times]public static void main(String args[]) {
839IRM@'5 [font="Times]int n = 10;
'C:>UlzLy [font="Times]while(n > 0) {
%ix)8+Eb [font="Times]System.out.println("tick " + n);
DVK)2La [font="Times]n--;
C#t'Y* [font="Times]}
9XRZ$j}L [font="Times]}
t7m>A-I [font="Times]}
|pmZ.r [font="Times] do…while 语句
LwK+:4$ [font="Times] class DoWhile {
(q4),y<:[ [font="Times]public static void main(String args[]) {
t@R
?Rgu3 [font="Times]int n = 10;
eOXHQjuj [font="Times]do {
&p}$J)q [font="Times]System.out.println("tick " + n);
n%k!vJ)] [font="Times]n--;
%c
[F;ug [font="Times]} while(n > 0);
BwBm[jtP [font="Times]}
a_ `[Lj [font="Times]}
GF>'\@Th 二者区别,[font="Times]do…while至少循环一次,而[font="Times]while的表达式要是为[font="Times]flase的话可以一次也不循环。再通俗一点,[font="Times]do…while就算是括号里的是[font="Times]flase,人家最少也能[font="Times]do一次。
7G\\{ [font="Times] for语句
't_[dSO [font="Times] class ForTick {
) :\xHR4 [font="Times]public static void main(String args[]) {
Q"t<3-" [font="Times]int n;
e?Ho a$k [font="Times]for(n=10; n>0; n--)
+\|Iu;w [font="Times]System.out.println("tick " + n);
_`I"0.B] [font="Times]}
59!Fkd3 [font="Times]}
LNa $
X5` 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。
`X`2:@gQ 还有啊,[font="Times]for循环的部分可以为空的
E[*Fz1> [font="Times]class ForVar {
aS pWsT [font="Times]public static void main(String args[]) {
#F*1V(! [font="Times]int i;
,daKC [font="Times]boolean done = false;
KM!k$;my [font="Times]i = 0;
Fb4`| [font="Times]for( ; !done; ) {
UY <e&Npo [font="Times]System.out.println("i is " + i);
FI<q@HF [font="Times]if(i == 10) done = true;
x,otFp [font="Times]i++;
~,BIf+\XF [font="Times]}
g*F '[Z." [font="Times]}
/-qxS <?o [font="Times]}
循环语句的例子下载 :LQ5u[g$\ [font="Times] 2.分支语句[font="Times]
h~(D@/tB [font="Times] if/else语句
!O#dV1wAa [font="Times]class IfElse {
)DeA}e?F [font="Times]public static void main(String args[]) {
H.WE6 [font="Times]int month = 4; // April
#Ap;_XcKw [font="Times]String season;
5i-Rglo [font="Times]if(month == 12 || month == 1 || month == 2)
qpsvi.S [font="Times]season = "Winter";
L9@&2?k [font="Times]else if(month == 3 || month == 4 || month == 5)
PIWux{ [font="Times]season = "Spring";
9!Ar`Io2@ [font="Times]else if(month == 6 || month == 7 || month == 8)
\MmI`$ [font="Times]season = "Summer";
w1Ec_y { [font="Times]else if(month == 9 || month == 10 || month == 11)
>^Yq|~[ [font="Times]season = "Autumn";
DF
g,Xa# [font="Times]else
h^*4}GU [font="Times]season = "Bogus Month";
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F>1vH [font="Times]System.out.println("April is in the " + season + ".");
hTM[8 ~<^ [font="Times]}
V~hlq$jn<Y [font="Times]}
PZm:T+5H [font="Times]//这段程序输出[font="Times]:
Y)$ ;Ax-D [font="Times]//April is in the Spring.
#."Hh<C [font="Times]// 注意[font="Times] “[font="Times]||”是或运算
3`#6ACF [font="Times] switch语句
(lGaPMEU} [font="Times] class Switch {
6sE{{,OGB [font="Times]public static void main(String args[]) {
!p[9{U->o; [font="Times]int month = 4;
2PeR [font="Times]String season;
E^rbcGJ [font="Times]switch (month) {
=Me5ftw [font="Times]case 12:
sj8~?O [font="Times]case 1:
Ht-t1q [font="Times]case 2:
[b/k3&O' [font="Times]season = "Winter";
tBm_YP[ [font="Times]break;
i:cXwQG}B [font="Times]case 3:
vNeCpf [font="Times]case 4:
.!6>oL/iF [font="Times]case 5:
tU^kQR! [font="Times]season = "Spring";
+4,2<\fX [font="Times]break;
5hbJOo0BZ [font="Times]case 6:
h8X g`C\ [font="Times]case 7:
$rhgzpZ!X_ [font="Times]case 8:
e{A9r@p! [font="Times]season = "Summer";
+MB!B9M@ [font="Times]break;
[F*4EGB [font="Times]case 9:
[ G
e=kFB [font="Times]case 10:
-PnyZ2'Z [font="Times]case 11:
Wfz\`y [font="Times]season = "Autumn";
DEw8*MN [font="Times]break;
s%!`kWVJ. [font="Times]default:
/% I7Vc [font="Times]season = "Bogus Month";
N~ ?{UOZd [font="Times]}
; h`0ir4[A [font="Times]System.out.println("April is in the " + season + ".");
)m&U#S _; [font="Times]}
H%1$,]F [font="Times]}
分支语句代码下载 Maqf[
Vky C'!;J [font="Times]switch语句适合于条件非常多的逻辑
tdEnk.O 请看上述语句可以混合使用,请看
下载例子