全新java初学者实践教程6(Java SE5.0版)
Hm*#HT%# 基本语法3
RfRaWbn &N ;6G`3 4*W7{MPY 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:
4iW2hV@m `_`,XkpzCJ [font="Times] 1.循环语句[font="Times]:while,do-while,for
lh5d6VUA XU7bWafy [font="Times]2.分支语句[font="Times]:if-else,switch,
RoZV6U~ [font="Times]
p6)UR~9Rs 3.跳转语句[font="Times] break,continue,label: 和[font="Times]return
K e8cfd~c [font="Times]
_3S{n=9 4.异常处理语句[font="Times]:try-catch-finally,throw
pnU
g:R@ .YRSd 实践:
(C%'I [font="Times] 1.循环语句
*93 N0m4Rl [font="Times] while 语句
&EOh}O< [font="Times]class While {
}dM^6
Kd% [font="Times]public static void main(String args[]) {
b.;W|$ . [font="Times]int n = 10;
Jt8 v=<@ [font="Times]while(n > 0) {
}o4Cd$,8 [font="Times]System.out.println("tick " + n);
IpxjP\ [font="Times]n--;
u@B"*V~K [font="Times]}
%ZK}y{u\ [font="Times]}
DVl:s [font="Times]}
-tQ|&fl [font="Times] do…while 语句
Jk*MxlA.b [font="Times] class DoWhile {
=F4} [font="Times]public static void main(String args[]) {
lLhCk>a [font="Times]int n = 10;
2 OTpGl [font="Times]do {
guvQISQlY [font="Times]System.out.println("tick " + n);
vkK+
C~" [font="Times]n--;
|=POV]K [font="Times]} while(n > 0);
KJiwM(o [font="Times]}
EIRf6jL [font="Times]}
5z_) 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。
c
z|IBsa* [font="Times] for语句
w3@te\ [font="Times] class ForTick {
& \m\QI [font="Times]public static void main(String args[]) {
$c-3Q|C [font="Times]int n;
he Wb(E& [font="Times]for(n=10; n>0; n--)
y^Lw7 [font="Times]System.out.println("tick " + n);
&ly[mBP~ [font="Times]}
[H1NP'Kg] [font="Times]}
}W<L;yD 与上面那两个的区别,[font="Times]for循环执行的次数是可以在执行之前确定的。通俗一点说吧,看这个例子[font="Times] for(n=10; n>0; n--)就是在括号里的时候,就已经知道要循环[font="Times]10次了。
7}Sw(g)o7 还有啊,[font="Times]for循环的部分可以为空的
5IMH G%W7 [font="Times]class ForVar {
_MU'he^W [font="Times]public static void main(String args[]) {
[H6>] & [font="Times]int i;
RC 48e._t [font="Times]boolean done = false;
c nzPq\ [font="Times]i = 0;
IQDWH/c [font="Times]for( ; !done; ) {
R|suBF3 [font="Times]System.out.println("i is " + i);
i]nE86.;
[font="Times]if(i == 10) done = true;
luMNi^FQ [font="Times]i++;
II91Ia [font="Times]}
dZW:Cf 9K [font="Times]}
^tv*I~>J! [font="Times]}
循环语句的例子下载 1}6pq2 [font="Times] 2.分支语句[font="Times]
2B4c:jJ [font="Times] if/else语句
K +~ [font="Times]class IfElse {
Y'-Lt5SCS [font="Times]public static void main(String args[]) {
1pV"<,t [font="Times]int month = 4; // April
(\}IOCNS [font="Times]String season;
`G'V9Xs( [font="Times]if(month == 12 || month == 1 || month == 2)
^tah4QmUA [font="Times]season = "Winter";
>b?,zWiw [font="Times]else if(month == 3 || month == 4 || month == 5)
6-3l6q [font="Times]season = "Spring";
)oj`K,# [font="Times]else if(month == 6 || month == 7 || month == 8)
d^w_rL [font="Times]season = "Summer";
^T5c^ M8o [font="Times]else if(month == 9 || month == 10 || month == 11)
z'fS%uI [font="Times]season = "Autumn";
g5E]o) [font="Times]else
)L{\k$r!EM [font="Times]season = "Bogus Month";
?d%_o@ [font="Times]System.out.println("April is in the " + season + ".");
NB^.$39n [font="Times]}
Cdv TC`~, [font="Times]}
4Mprc~ 7vr [font="Times]//这段程序输出[font="Times]:
`drvu?F [font="Times]//April is in the Spring.
x!< C0N>?z [font="Times]// 注意[font="Times] “[font="Times]||”是或运算
4MM#\ [font="Times] switch语句
eN$~@'w [font="Times] class Switch {
B0Z@ Cf [font="Times]public static void main(String args[]) {
_ehU:3L`s [font="Times]int month = 4;
=3"Nn4Z [font="Times]String season;
j.z#fU [font="Times]switch (month) {
6+It>mnR
[font="Times]case 12:
1kpI?Plki [font="Times]case 1:
@ +7'0[y? [font="Times]case 2:
%=]{~5f> [font="Times]season = "Winter";
1t)6wk
N [font="Times]break;
B4.hJZ5 [font="Times]case 3:
gs!{'=4wT [font="Times]case 4:
C{c (K! [font="Times]case 5:
>fjf]
6 [font="Times]season = "Spring";
mz#(\p=T [font="Times]break;
&~k/G [font="Times]case 6:
zYep
V [font="Times]case 7:
?LZ)r^ger [font="Times]case 8:
oCduY2 [font="Times]season = "Summer";
nyIb8=f [font="Times]break;
cZwQ{9> [font="Times]case 9:
RH`m=?~J, [font="Times]case 10:
tHGK<rb [font="Times]case 11:
4y knX%[ [font="Times]season = "Autumn";
mV;7SBoT [font="Times]break;
Y)uNzb6R [font="Times]default:
@<};Bo' [font="Times]season = "Bogus Month";
.z_^_@qdm [font="Times]}
bDr'W [font="Times]System.out.println("April is in the " + season + ".");
4
Hu+ljdjB [font="Times]}
J)R2O4OEd [font="Times]}
分支语句代码下载 /aK },+ t >8t|t+ [font="Times]switch语句适合于条件非常多的逻辑
a#kZY7s 请看上述语句可以混合使用,请看
下载例子