全新java初学者实践教程6(Java SE5.0版)
~m_{&,CA. 基本语法3
O}>@G l^Ob60)2 793 15A 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:
>TMd1?, LN~mKoW [font="Times] 1.循环语句[font="Times]:while,do-while,for
]DKRug5 Q 9fK)j1$ [font="Times]2.分支语句[font="Times]:if-else,switch,
nfbR"E
jXr [font="Times]
58XZ]Mc0 3.跳转语句[font="Times] break,continue,label: 和[font="Times]return
" i:[|7 [font="Times]
q>Di|5<y 4.异常处理语句[font="Times]:try-catch-finally,throw
3_<l`6^Ns/ ").gPmC 实践:
TG[u3Y4 [font="Times] 1.循环语句
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3i\j [font="Times] while 语句
0N^+d,Xt. [font="Times]class While {
ltfKqY- [font="Times]public static void main(String args[]) {
<3!Al,!ej@ [font="Times]int n = 10;
)by7[I0v [font="Times]while(n > 0) {
Tf~eH!~0 [font="Times]System.out.println("tick " + n);
iLch3[p% [font="Times]n--;
.<zKBv [font="Times]}
d\uN [font="Times]}
~n-Px) [font="Times]}
XVkw/l [font="Times] do…while 语句
+}O -WX? [font="Times] class DoWhile {
#B<EMGH [font="Times]public static void main(String args[]) {
}[Z'Sg]s [font="Times]int n = 10;
g3].STz6w [font="Times]do {
OKAU*}_ [font="Times]System.out.println("tick " + n);
9j|v
D [font="Times]n--;
+@=V}IO [font="Times]} while(n > 0);
yAfwQ$Ll7 [font="Times]}
q[_qZ [font="Times]}
yfK}1mx)j 二者区别,[font="Times]do…while至少循环一次,而[font="Times]while的表达式要是为[font="Times]flase的话可以一次也不循环。再通俗一点,[font="Times]do…while就算是括号里的是[font="Times]flase,人家最少也能[font="Times]do一次。
VxBBZsZO~ [font="Times] for语句
;+<IWDo [font="Times] class ForTick {
}%p:Xv@X! [font="Times]public static void main(String args[]) {
I%u 2 ce [font="Times]int n;
"Yh;3tI4* [font="Times]for(n=10; n>0; n--)
GQ;0KIN [font="Times]System.out.println("tick " + n);
n1J u=C [font="Times]}
kh9'W<tE [font="Times]}
u Jqv@GFv 与上面那两个的区别,[font="Times]for循环执行的次数是可以在执行之前确定的。通俗一点说吧,看这个例子[font="Times] for(n=10; n>0; n--)就是在括号里的时候,就已经知道要循环[font="Times]10次了。
o>_})WM1[ 还有啊,[font="Times]for循环的部分可以为空的
rw,Ylr:3 [font="Times]class ForVar {
])wdd>' [font="Times]public static void main(String args[]) {
@>HTbs6W [font="Times]int i;
i+h*<){X [font="Times]boolean done = false;
iI{L>
[font="Times]i = 0;
<mQXS87 [font="Times]for( ; !done; ) {
LP6p [font="Times]System.out.println("i is " + i);
l3sF/zkH [font="Times]if(i == 10) done = true;
|]4!WBK [font="Times]i++;
T[Zs{S [font="Times]}
HwHF8#D*l [font="Times]}
O;~e^ <* [font="Times]}
循环语句的例子下载 }3^m>i*8 [font="Times] 2.分支语句[font="Times]
*[{j'7*cc [font="Times] if/else语句
sSh{.XuB+3 [font="Times]class IfElse {
sqrLys_S [font="Times]public static void main(String args[]) {
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F 0 [font="Times]int month = 4; // April
QQBh)5F [font="Times]String season;
QkBw59L7 [font="Times]if(month == 12 || month == 1 || month == 2)
E
+_n@t" [font="Times]season = "Winter";
<%m YsaM [font="Times]else if(month == 3 || month == 4 || month == 5)
+b(};(wL [font="Times]season = "Spring";
i'm<{v [font="Times]else if(month == 6 || month == 7 || month == 8)
5Jbwl$mZ [font="Times]season = "Summer";
^1najUpQ_n [font="Times]else if(month == 9 || month == 10 || month == 11)
$DoR@2~y [font="Times]season = "Autumn";
-N8rs[c [font="Times]else
x="Wqcnj{ [font="Times]season = "Bogus Month";
B+K6(^j,,y [font="Times]System.out.println("April is in the " + season + ".");
Q,[G?vbj [font="Times]}
"E(i< [font="Times]}
o/w3b8 [font="Times]//这段程序输出[font="Times]:
6;Z-Y>\c [font="Times]//April is in the Spring.
+4s]#{mP [font="Times]// 注意[font="Times] “[font="Times]||”是或运算
$Z:O&sD{ [font="Times] switch语句
2)n`Bd [font="Times] class Switch {
o]4]fLQ [font="Times]public static void main(String args[]) {
x~V[}4E%> [font="Times]int month = 4;
3PE.7-HF [font="Times]String season;
4yxQq7
m, [font="Times]switch (month) {
0G+Q^]0 [font="Times]case 12:
nF@**,C Q [font="Times]case 1:
@|\9<S [font="Times]case 2:
R9U{r.AA [font="Times]season = "Winter";
3>KEl^1DB [font="Times]break;
c_3B: F7 [font="Times]case 3:
S@/{34, [font="Times]case 4:
WO_Uc_R [font="Times]case 5:
/W/e%. [font="Times]season = "Spring";
jVQy{8{G [font="Times]break;
IMkE~0x4</ [font="Times]case 6:
oX|T&"& [font="Times]case 7:
e9o\qEm [font="Times]case 8:
xqt?z n [font="Times]season = "Summer";
$fmTa02q> [font="Times]break;
`,qft[1 [font="Times]case 9:
(QDKw}O2b [font="Times]case 10:
!;eE7xn & [font="Times]case 11:
L,}'ST [font="Times]season = "Autumn";
g'7E6n"!, [font="Times]break;
+>"s)R43 [font="Times]default:
1,-C*T}nR [font="Times]season = "Bogus Month";
ye(b 7CX [font="Times]}
jr=9.=jI8k [font="Times]System.out.println("April is in the " + season + ".");
&DLWlMGq [font="Times]}
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wU [font="Times]}
分支语句代码下载 h p]J>i. 7?*+,Fo# [font="Times]switch语句适合于条件非常多的逻辑
i g(O$y 请看上述语句可以混合使用,请看
下载例子