全新java初学者实践教程6(Java SE5.0版)
`ZHP1uQ< 基本语法3
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% 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:
t> Q{yw x49!{} [font="Times] 1.循环语句[font="Times]:while,do-while,for
J$uM 03 ~HLRfL? [font="Times]2.分支语句[font="Times]:if-else,switch,
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RcY[rnI6 3.跳转语句[font="Times] break,continue,label: 和[font="Times]return
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s(@h 2:j 4.异常处理语句[font="Times]:try-catch-finally,throw
f%^'P"R )jW(6 实践:
kv|,b [font="Times] 1.循环语句
_ P ,@ [font="Times] while 语句
ESQ!@G/n [font="Times]class While {
O?K./So& [font="Times]public static void main(String args[]) {
Wz=OSH7"f [font="Times]int n = 10;
u,i]a#K [font="Times]while(n > 0) {
$7gB_o$zz [font="Times]System.out.println("tick " + n);
Uf,fX/:! [font="Times]n--;
;'kI/(;;C [font="Times]}
T@+ClZi [font="Times]}
HR{s&ho [font="Times]}
6o}V@UzqV [font="Times] do…while 语句
#0y<a:}R [font="Times] class DoWhile {
c c G['7 [font="Times]public static void main(String args[]) {
f>iuHR*EXB [font="Times]int n = 10;
7s>a2 [font="Times]do {
r7z6___ [font="Times]System.out.println("tick " + n);
G\Hq/4 [font="Times]n--;
vP]9;mQ [font="Times]} while(n > 0);
(}H ,ng'4 [font="Times]}
@h-T:$ [font="Times]}
6TFo|z!C 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。
k'13f,o} [font="Times] for语句
bAhZ7;T~ [font="Times] class ForTick {
X B I;Lg [font="Times]public static void main(String args[]) {
")\aJ8 [font="Times]int n;
W}gVIfe [font="Times]for(n=10; n>0; n--)
lJ/6-dP [font="Times]System.out.println("tick " + n);
~Yk"Hos [font="Times]}
+mWjBY [font="Times]}
*re 44 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。
7c1+t_ Ew 还有啊,[font="Times]for循环的部分可以为空的
8GB]95JWwp [font="Times]class ForVar {
;<6"JP>0 [font="Times]public static void main(String args[]) {
Du_$C[ [font="Times]int i;
v4<j [font="Times]boolean done = false;
Zw=G@4xoU [font="Times]i = 0;
mx tgb$* [font="Times]for( ; !done; ) {
iz
x[ [font="Times]System.out.println("i is " + i);
J%P)%yX [font="Times]if(i == 10) done = true;
S=9E@(] [font="Times]i++;
b~wKF0vq [font="Times]}
'C]jwxy [font="Times]}
?MZ:_'2p [font="Times]}
循环语句的例子下载 gRvJ.Q {h [font="Times] 2.分支语句[font="Times]
qpgU8f [font="Times] if/else语句
70`M,`` [font="Times]class IfElse {
+{>.Sk'$ [font="Times]public static void main(String args[]) {
_"f<Ol[! [font="Times]int month = 4; // April
<q6`~F~| [font="Times]String season;
0/A-#'> [font="Times]if(month == 12 || month == 1 || month == 2)
2ij/N%l [font="Times]season = "Winter";
U>3
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[font="Times]else if(month == 3 || month == 4 || month == 5)
.ev\M0Dt [font="Times]season = "Spring";
n&7@@@cA [font="Times]else if(month == 6 || month == 7 || month == 8)
Fzs>J&sY& [font="Times]season = "Summer";
]7<m1Lg
[font="Times]else if(month == 9 || month == 10 || month == 11)
N{pa)
/ [font="Times]season = "Autumn";
D0M!"c>\ [font="Times]else
GVp [font="Times]season = "Bogus Month";
hmzair3X [font="Times]System.out.println("April is in the " + season + ".");
-Op@y2+c [font="Times]}
ABiC9[Q0 [font="Times]}
-- S"w@ [font="Times]//这段程序输出[font="Times]:
lZ a?Y@ [font="Times]//April is in the Spring.
vahf]2jEB [font="Times]// 注意[font="Times] “[font="Times]||”是或运算
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_5- [font="Times] switch语句
u[[/w&UV., [font="Times] class Switch {
( -2R{!A [font="Times]public static void main(String args[]) {
}:^X X0:FK [font="Times]int month = 4;
KZ\dB;W<| [font="Times]String season;
sA2o2~AmM [font="Times]switch (month) {
jEE_D +K [font="Times]case 12:
Q!)z)-hI [font="Times]case 1:
bw;iz,Z [font="Times]case 2:
1}DerX 6 [font="Times]season = "Winter";
:|($,3* [font="Times]break;
It\BbG= [font="Times]case 3:
-d_ 7*>m$ [font="Times]case 4:
&Q+]t"OA! [font="Times]case 5:
w%~qB5wF6 [font="Times]season = "Spring";
Zjt9vS) [font="Times]break;
R`3x=q
[font="Times]case 6:
JJNmpUJ [font="Times]case 7:
[J:zE&aj [font="Times]case 8:
ahoh9iJ [font="Times]season = "Summer";
cUVTRWV [font="Times]break;
}wG|%Y#+r [font="Times]case 9:
"S|(4BUJ( [font="Times]case 10:
~FNPD'`t [font="Times]case 11:
]TfeBX6ST [font="Times]season = "Autumn";
;>/ipnx [font="Times]break;
/MqP[*L [font="Times]default:
w*2^/zh [font="Times]season = "Bogus Month";
+DxifXtB [font="Times]}
9dw0<qw1% [font="Times]System.out.println("April is in the " + season + ".");
?:JdRnH \ [font="Times]}
:7k`R62{ [font="Times]}
分支语句代码下载 ;$[VX/A`f QS%,7'EG [font="Times]switch语句适合于条件非常多的逻辑
wK ][qZ ] 请看上述语句可以混合使用,请看
下载例子