全新java初学者实践教程6(Java SE5.0版)
@ZX{q~g! 基本语法3
GSpS8wWD } v8pUt\m" jl:O~UL6i 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:
xR1g 09x\i/nb [font="Times] 1.循环语句[font="Times]:while,do-while,for
5l)p5Bb48c ih~c(&n0 [font="Times]2.分支语句[font="Times]:if-else,switch,
-F5U.6~`! [font="Times]
) mv}u~ 3.跳转语句[font="Times] break,continue,label: 和[font="Times]return
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[;I.aT}R!; 4.异常处理语句[font="Times]:try-catch-finally,throw
~r=TVHjqi |:
nuT$( 实践:
:;??!V [font="Times] 1.循环语句
>Zmpsa+ [font="Times] while 语句
fDbs3"H Q [font="Times]class While {
m+uh6IqN./ [font="Times]public static void main(String args[]) {
F ^E(AE [font="Times]int n = 10;
*O 0* [font="Times]while(n > 0) {
)k7`!@ID [font="Times]System.out.println("tick " + n);
yUH8 [font="Times]n--;
KrbNo$0% [font="Times]}
y?5*K [font="Times]}
r0S7e3xb [font="Times]}
@H{$,\\ [font="Times] do…while 语句
]L_HnmD6 [font="Times] class DoWhile {
K"=v|a. [font="Times]public static void main(String args[]) {
d[SC1J [font="Times]int n = 10;
8Q6il- [font="Times]do {
S2fw"1h*x [font="Times]System.out.println("tick " + n);
)Ba^Igb} [font="Times]n--;
/!%P7F [font="Times]} while(n > 0);
8n&" ,)U [font="Times]}
EkTen:{G [font="Times]}
P, S9gG9 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。
4AF"+L [font="Times] for语句
f-{[ushj [font="Times] class ForTick {
IndNR:"g [font="Times]public static void main(String args[]) {
EO|
kiC [font="Times]int n;
`_v-Y`Z [font="Times]for(n=10; n>0; n--)
S?8q.59 [font="Times]System.out.println("tick " + n);
H!45w;,I [font="Times]}
,#"AWQ [font="Times]}
JBWiTUk 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。
ZFdQZ=.' 还有啊,[font="Times]for循环的部分可以为空的
gV`:eNo* [font="Times]class ForVar {
sO(K po9jq [font="Times]public static void main(String args[]) {
s;5PHweWf [font="Times]int i;
JL(*peeu3 [font="Times]boolean done = false;
wT.V3G [font="Times]i = 0;
nt5 ~"8 [font="Times]for( ; !done; ) {
BO{J{ [font="Times]System.out.println("i is " + i);
L;z-,U$;%R [font="Times]if(i == 10) done = true;
_<3:vyfdC [font="Times]i++;
N?pD"re)6 [font="Times]}
oW/&X5 [font="Times]}
xH'H!
8 [font="Times]}
循环语句的例子下载 +Oyt [font="Times] 2.分支语句[font="Times]
Qy3e,9nS [font="Times] if/else语句
q2hZ1o [font="Times]class IfElse {
x b _C1n [font="Times]public static void main(String args[]) {
4&$G;?#W2 [font="Times]int month = 4; // April
b1 KiO2
E [font="Times]String season;
}wv$ #H[ [font="Times]if(month == 12 || month == 1 || month == 2)
#lB[]2]N [font="Times]season = "Winter";
_;@kS<\N [font="Times]else if(month == 3 || month == 4 || month == 5)
|r
/}r,t} [font="Times]season = "Spring";
dmF<J>[ [font="Times]else if(month == 6 || month == 7 || month == 8)
c/x(v=LW [font="Times]season = "Summer";
$[|8bE [font="Times]else if(month == 9 || month == 10 || month == 11)
"0/OpT7h7 [font="Times]season = "Autumn";
n1cAI|ZE [font="Times]else
y'zEaL&SI@ [font="Times]season = "Bogus Month";
atN`w=6A` [font="Times]System.out.println("April is in the " + season + ".");
Nq9(O#} [font="Times]}
N[42al [font="Times]}
-}N{'S,Bp [font="Times]//这段程序输出[font="Times]:
HV?awc [font="Times]//April is in the Spring.
1DLQZq [font="Times]// 注意[font="Times] “[font="Times]||”是或运算
H$[--_dI{ [font="Times] switch语句
WrD20Q$9Q [font="Times] class Switch {
{)%B?75~ [font="Times]public static void main(String args[]) {
c9'#G>&h~^ [font="Times]int month = 4;
/Fv1Z=:r [font="Times]String season;
zBoU;d%p> [font="Times]switch (month) {
}~ + [font="Times]case 12:
JT:9"lmJz, [font="Times]case 1:
Az)P&*2:'` [font="Times]case 2:
;N/c 5+ [font="Times]season = "Winter";
wvc?2~` [font="Times]break;
r^\^*FD | [font="Times]case 3:
Q 5jP`<zWU [font="Times]case 4:
Z]Qm64^I [font="Times]case 5:
Y@r#:BH) [font="Times]season = "Spring";
o 86}NqK [font="Times]break;
kv'n W [font="Times]case 6:
{QhvHV [font="Times]case 7:
D!X{9q}S1 [font="Times]case 8:
-iW[cj
R`$ [font="Times]season = "Summer";
wLgRI$_Dm [font="Times]break;
=tog<7 [font="Times]case 9:
c`t1:%S [font="Times]case 10:
4 5Ql7~ [font="Times]case 11:
{`3;Pd` [font="Times]season = "Autumn";
De^is^{ [font="Times]break;
#~#_)\l'F [font="Times]default:
nxH$$}9 [font="Times]season = "Bogus Month";
r^
"mPgY [font="Times]}
yDyq. -Q [font="Times]System.out.println("April is in the " + season + ".");
V*)6!N[5 [font="Times]}
{$s:N&5 [font="Times]}
分支语句代码下载 r]]Ke_s! ~q1s4^J [font="Times]switch语句适合于条件非常多的逻辑
r7IhmdA 请看上述语句可以混合使用,请看
下载例子