全新java初学者实践教程6(Java SE5.0版)
]99|KQ<s 基本语法3
$>G8_q wYdb*"R QFE:tBHe 我们这个教程侧重的是实践的内容和语言的重点。在[font="Times]java语言中还有很多细节的东西,请参考[font="Times]sun公司的官方培训教程。我们这里不能一一讲述。这节课我们来给大家提供一些程序流程控制的一些例子供大家学习。计算机怎么做事情,是我们教给他的。我们用它解决实际生活中的问题,所以计算机要描述现实生活中的流程。[font="Times]Java语言中提供了[font="Times]4类程序控制语句,来描述流程:
6O|@xvg jGJLSEe_ [font="Times] 1.循环语句[font="Times]:while,do-while,for
.I$qCb|FP kd>hhiz| [font="Times]2.分支语句[font="Times]:if-else,switch,
j1^I+j) [font="Times]
1!ii;s^e 3.跳转语句[font="Times] break,continue,label: 和[font="Times]return
R"4Vtww [font="Times]
1=r#d-\tR 4.异常处理语句[font="Times]:try-catch-finally,throw
5rwu!Y;7* -]L6= 实践:
v;BV@E0}x [font="Times] 1.循环语句
Ld\R:{M" [font="Times] while 语句
aL*&r~`&e' [font="Times]class While {
Mh~q// [font="Times]public static void main(String args[]) {
Olt`:;j- [font="Times]int n = 10;
) dn(G@5 [font="Times]while(n > 0) {
t
4PK}>QW [font="Times]System.out.println("tick " + n);
bhID#& [font="Times]n--;
.O74V~T [font="Times]}
pqk?|BvpK_ [font="Times]}
H0:E(}@ [font="Times]}
gGvz(R:y [font="Times] do…while 语句
c*(bO3 b [font="Times] class DoWhile {
J\/cCW-rF [font="Times]public static void main(String args[]) {
w&X<5'GM [font="Times]int n = 10;
lun#^ J [font="Times]do {
1uG"f<TsR [font="Times]System.out.println("tick " + n);
"&%I)e^ [font="Times]n--;
0+iu(VbF [font="Times]} while(n > 0);
Y}x>t* I [font="Times]}
4^:\0UF [font="Times]}
4Z1ST; 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。
vY4\59]P [font="Times] for语句
ztnFhJ<a$ [font="Times] class ForTick {
MPCBT!o4Z [font="Times]public static void main(String args[]) {
M:XSQ["6>V [font="Times]int n;
U [*FCD!~ [font="Times]for(n=10; n>0; n--)
qT,Te [font="Times]System.out.println("tick " + n);
fg
s!v7 [font="Times]}
5"^en# ?9 [font="Times]}
:imW\@u 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。
?Q sQnQ 还有啊,[font="Times]for循环的部分可以为空的
'GB.UKlR [font="Times]class ForVar {
YbR!+ 0\g [font="Times]public static void main(String args[]) {
+lm{Olm'^ [font="Times]int i;
4F)-"ck [font="Times]boolean done = false;
.)RzT9sg [font="Times]i = 0;
vo`2\R. [font="Times]for( ; !done; ) {
05z,b]>l [font="Times]System.out.println("i is " + i);
kr+D,h01 [font="Times]if(i == 10) done = true;
6tB+J F [font="Times]i++;
E;,u2[3 [font="Times]}
$g/SWq [font="Times]}
.}&`TU [font="Times]}
循环语句的例子下载 }
uO);k5H [font="Times] 2.分支语句[font="Times]
e7@ojOQ% [font="Times] if/else语句
0vFD3}~> [font="Times]class IfElse {
FQm`~rA~zt [font="Times]public static void main(String args[]) {
>go,K{cK6 [font="Times]int month = 4; // April
7"aN#;& [font="Times]String season;
4\y/'`xm)6 [font="Times]if(month == 12 || month == 1 || month == 2)
2w59^"<, [font="Times]season = "Winter";
mlixIW2 [font="Times]else if(month == 3 || month == 4 || month == 5)
?a8^1: [font="Times]season = "Spring";
<d,b '<z
s [font="Times]else if(month == 6 || month == 7 || month == 8)
2#P*, [font="Times]season = "Summer";
3wOZ4<B
[font="Times]else if(month == 9 || month == 10 || month == 11)
M*!agh [font="Times]season = "Autumn";
lU@]@_< [font="Times]else
Xp >7iX!: [font="Times]season = "Bogus Month";
u&`XB|~ [font="Times]System.out.println("April is in the " + season + ".");
>CrA;\l [font="Times]}
<<@bl@9' [font="Times]}
5Eg1Q
YVt [font="Times]//这段程序输出[font="Times]:
1|RANy [font="Times]//April is in the Spring.
=5Q]m6-SgV [font="Times]// 注意[font="Times] “[font="Times]||”是或运算
[f)cL6AeF [font="Times] switch语句
\!>3SKs(e [font="Times] class Switch {
*#E
FsUw [font="Times]public static void main(String args[]) {
cU;iUf [font="Times]int month = 4;
}M1`di4e [font="Times]String season;
'3_]Gu-D [font="Times]switch (month) {
Ge2q% [font="Times]case 12:
*-MM<|Qt [font="Times]case 1:
O/,aJCe
[font="Times]case 2:
[p{#XwN [font="Times]season = "Winter";
s8wmCzB~ [font="Times]break;
61.Brp.eP [font="Times]case 3:
!6BW@GeF] [font="Times]case 4:
}3o|EXx= [font="Times]case 5:
W"zab [font="Times]season = "Spring";
Id'X*U7Q [font="Times]break;
0KYEb%44 [font="Times]case 6:
UmNa[s [font="Times]case 7:
)T';qm0w [font="Times]case 8:
RMK"o? [font="Times]season = "Summer";
eb.O#Y [font="Times]break;
3x5JFM [font="Times]case 9:
[baiH|5> [font="Times]case 10:
!+1<E*NQ S [font="Times]case 11:
uZc`jNc\ [font="Times]season = "Autumn";
.l>77zM6 [font="Times]break;
#z&&M"*a| [font="Times]default:
X*M#FT- [font="Times]season = "Bogus Month";
|kw)KEi}H [font="Times]}
}E0,z [font="Times]System.out.println("April is in the " + season + ".");
.Si,dc\ [font="Times]}
*FC=X) _&W [font="Times]}
分支语句代码下载 P\w\N2 eCN })An [font="Times]switch语句适合于条件非常多的逻辑
=+ytTQc*ot 请看上述语句可以混合使用,请看
下载例子