全新java初学者实践教程6(Java SE5.0版)
Oe*emUX7 基本语法3
X8p-VCkV De\&r~bTW9 Ll%[}C?~]? 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:
$^}?98m }"%tlU!} [font="Times] 1.循环语句[font="Times]:while,do-while,for
i,Yv 9>\s81^ [font="Times]2.分支语句[font="Times]:if-else,switch,
b=`h""u [font="Times]
xR\$2( 3.跳转语句[font="Times] break,continue,label: 和[font="Times]return
27G6C`} [font="Times]
TU7 Qt< 4.异常处理语句[font="Times]:try-catch-finally,throw
LEWeybT 8`kK)iCq 实践:
CR&v z3\Q [font="Times] 1.循环语句
-dZ7;n5&_ [font="Times] while 语句
0vt?yD [font="Times]class While {
R/xeC [r [font="Times]public static void main(String args[]) {
%fo +Y+t [font="Times]int n = 10;
U,~\}$<I [font="Times]while(n > 0) {
!z$.Jcr1 [font="Times]System.out.println("tick " + n);
Y6&w0~?! [font="Times]n--;
h /@G[5E [font="Times]}
zT*EpIa+LS [font="Times]}
Kbrb;r59 [font="Times]}
|fOQm [font="Times] do…while 语句
, 0MDkXb [font="Times] class DoWhile {
8|OsVIe% [font="Times]public static void main(String args[]) {
pMKnA.| [font="Times]int n = 10;
^ ,d!K2` [font="Times]do {
w:#yu [font="Times]System.out.println("tick " + n);
5_x8!v [font="Times]n--;
6`+dP"@ [font="Times]} while(n > 0);
1c8J yp [font="Times]}
V^As@P8,'( [font="Times]}
k$j>_U? P 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。
NDWpV [font="Times] for语句
v&;q4b4 [font="Times] class ForTick {
,dLh`t<\ [font="Times]public static void main(String args[]) {
%!mJnc% [font="Times]int n;
]EC zb/ [font="Times]for(n=10; n>0; n--)
@~qlSU& [font="Times]System.out.println("tick " + n);
n&jfJgD&g [font="Times]}
*?VbN}g2 [font="Times]}
DKx8<yEky 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。
L
Me{5H 还有啊,[font="Times]for循环的部分可以为空的
z}&?^YU*)` [font="Times]class ForVar {
L#1YR}m [font="Times]public static void main(String args[]) {
wKIQK!B)mF [font="Times]int i;
=c"`>Vi@d [font="Times]boolean done = false;
-1;BwlL [font="Times]i = 0;
5IE 2&V [font="Times]for( ; !done; ) {
tXV9+AJ [font="Times]System.out.println("i is " + i);
d<r=f" [font="Times]if(i == 10) done = true;
!ZJ"lm [font="Times]i++;
B\G?dmo [font="Times]}
}_vE
lBh6$ [font="Times]}
BxS\"W [font="Times]}
循环语句的例子下载 ]Nz~4ebB [font="Times] 2.分支语句[font="Times]
MkEr|w' [font="Times] if/else语句
%QCh#v=ks [font="Times]class IfElse {
@`^+XP K\ [font="Times]public static void main(String args[]) {
0&}
"!) [font="Times]int month = 4; // April
u%3D{Dj [font="Times]String season;
S!j=hj@qW [font="Times]if(month == 12 || month == 1 || month == 2)
d[9c6C:<q [font="Times]season = "Winter";
i<@6f'Kir [font="Times]else if(month == 3 || month == 4 || month == 5)
nlOM4fJ( [font="Times]season = "Spring";
1JMEniB+9 [font="Times]else if(month == 6 || month == 7 || month == 8)
p%pM3<p [font="Times]season = "Summer";
8D@H4O. [font="Times]else if(month == 9 || month == 10 || month == 11)
}RowAGWL [font="Times]season = "Autumn";
hy3j8?66 [font="Times]else
;}"_hLX [font="Times]season = "Bogus Month";
[p^N].K$ [font="Times]System.out.println("April is in the " + season + ".");
X`JWYb4 [font="Times]}
"7mYs)= [font="Times]}
RB`Emp&T [font="Times]//这段程序输出[font="Times]:
GVP"~I~/: [font="Times]//April is in the Spring.
]r8t^bqe [font="Times]// 注意[font="Times] “[font="Times]||”是或运算
pC2ZN [font="Times] switch语句
[DpGL/Y. [font="Times] class Switch {
e[.c^Hw [font="Times]public static void main(String args[]) {
jT}3Zn [font="Times]int month = 4;
A[`c2v-hF [font="Times]String season;
QV,X> !Nz [font="Times]switch (month) {
'Alt+O_ [font="Times]case 12:
J6r"_>)z [font="Times]case 1:
bw\fKZ [font="Times]case 2:
&MKG#Y} [font="Times]season = "Winter";
3z';Zwz &X [font="Times]break;
+LuGjDn0 [font="Times]case 3:
EhL
8rR [font="Times]case 4:
KJ M:-z@ [font="Times]case 5:
ufyqfID [font="Times]season = "Spring";
eM
Ym@~4 [font="Times]break;
Y /$`vgqs [font="Times]case 6:
=@q 9,H [font="Times]case 7:
q<