全新java初学者实践教程6(Java SE5.0版)
Z jmQ 基本语法3
I Id4w~| ZMQ=D!kT r>fGj\#R = 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:
{]+t< Sy VGm@ [font="Times] 1.循环语句[font="Times]:while,do-while,for
Wu{=QjgY eMRH*MyD [font="Times]2.分支语句[font="Times]:if-else,switch,
B`mJT*B[ [font="Times]
j"nOxs 3.跳转语句[font="Times] break,continue,label: 和[font="Times]return
W+&5G(z~ [font="Times]
d AcSG 4.异常处理语句[font="Times]:try-catch-finally,throw
I5M\PK/ KzVi:Hm 实践:
^;_~mq. [font="Times] 1.循环语句
~snj92K [font="Times] while 语句
L"&T3i [font="Times]class While {
Z8v 8@Y [font="Times]public static void main(String args[]) {
cR3d&/_,U [font="Times]int n = 10;
es*$/A [font="Times]while(n > 0) {
Dylm=ZZa [font="Times]System.out.println("tick " + n);
9;#RzelSp [font="Times]n--;
AI2XNSV@Yl [font="Times]}
OPNRBMD [font="Times]}
y`va6 %u{ [font="Times]}
uHI(-!O [font="Times] do…while 语句
-!XG>Z [font="Times] class DoWhile {
]B3](TH" [font="Times]public static void main(String args[]) {
W,@F!8 [font="Times]int n = 10;
V#oz~GMB [font="Times]do {
x{:U$[_ [font="Times]System.out.println("tick " + n);
w!"L\QT [font="Times]n--;
C{bxPILw [font="Times]} while(n > 0);
&DMC\R* j [font="Times]}
FY'0?CT$ [font="Times]}
Q~]oN 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。
x1eC r_ [font="Times] for语句
(%fQhQ [font="Times] class ForTick {
ts~VO` [font="Times]public static void main(String args[]) {
{\(G^B*\ [font="Times]int n;
C*2%Ix18+N [font="Times]for(n=10; n>0; n--)
^f,4=- [font="Times]System.out.println("tick " + n);
!Axe}RD' [font="Times]}
!}!KT(%% [font="Times]}
:C_/K(Rkl 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。
D
5r H6*J 还有啊,[font="Times]for循环的部分可以为空的
i%9vZ [font="Times]class ForVar {
m ~&
[font="Times]public static void main(String args[]) {
\( s `=(t [font="Times]int i;
FFqK tj's [font="Times]boolean done = false;
kD#n/RBgf [font="Times]i = 0;
\< .BN;t{ [font="Times]for( ; !done; ) {
y[XD=j [font="Times]System.out.println("i is " + i);
st)is4 [font="Times]if(i == 10) done = true;
0ZjT.Ep [font="Times]i++;
iL;V5|(sb [font="Times]}
NAD^10 [font="Times]}
~5HT_B U= [font="Times]}
循环语句的例子下载 %<>:$4U@] [font="Times] 2.分支语句[font="Times]
|1%%c
% [font="Times] if/else语句
t+KW=eW [font="Times]class IfElse {
%!\=$ s}g [font="Times]public static void main(String args[]) {
5b:1+5iF- [font="Times]int month = 4; // April
?V2P]| [font="Times]String season;
9&*
7+! [font="Times]if(month == 12 || month == 1 || month == 2)
L"'=[O~ [font="Times]season = "Winter";
-4x! #|] [font="Times]else if(month == 3 || month == 4 || month == 5)
Dd1k? [font="Times]season = "Spring";
<~dfp [font="Times]else if(month == 6 || month == 7 || month == 8)
QG*hQh
[font="Times]season = "Summer";
FXr^ 4B} [font="Times]else if(month == 9 || month == 10 || month == 11)
^(TCUY~f& [font="Times]season = "Autumn";
J920A^)j! [font="Times]else
L~5f*LE$1 [font="Times]season = "Bogus Month";
3g;Y [font="Times]System.out.println("April is in the " + season + ".");
d7kE}{, [font="Times]}
/
<(|4e [font="Times]}
~3bV~H#~m [font="Times]//这段程序输出[font="Times]:
0G8@UJv6 [font="Times]//April is in the Spring.
Xgx/ubca0 [font="Times]// 注意[font="Times] “[font="Times]||”是或运算
_5 Lcr) [font="Times] switch语句
|6Y:W$7k [font="Times] class Switch {
us.[wp'Sh [font="Times]public static void main(String args[]) {
dLYM )-H`> [font="Times]int month = 4;
,&,%B|gT] [font="Times]String season;
1R}9k)JQ [font="Times]switch (month) {
n=-vOa% [font="Times]case 12:
(LK@w9)i; [font="Times]case 1:
!U?C_ [font="Times]case 2:
Y)k"KRW+ [font="Times]season = "Winter";
Ze%S<xT!O [font="Times]break;
K ar! [font="Times]case 3:
p1'q{E+o* [font="Times]case 4:
vT#R>0@mi [font="Times]case 5:
q%G[tXw [font="Times]season = "Spring";
B5 /8LEWw [font="Times]break;
"1gIR^S%9 [font="Times]case 6:
s#5#WNzP [font="Times]case 7:
1?QVtfwY [font="Times]case 8:
|WaWmp(pQ [font="Times]season = "Summer";
<*J"6x [font="Times]break;
@rT$}O1?` [font="Times]case 9:
F2zo
!a8 [font="Times]case 10:
oqvu8" [font="Times]case 11:
93n%:?l"<W [font="Times]season = "Autumn";
;}6wj@8He [font="Times]break;
L&+k`b [font="Times]default:
0i}.l\ [font="Times]season = "Bogus Month";
bDDP:INm. [font="Times]}
Y"t|0dO%b [font="Times]System.out.println("April is in the " + season + ".");
dXDyY [font="Times]}
q2xAx1R`sV [font="Times]}
分支语句代码下载 iY`[dsT #q:j~4)h [font="Times]switch语句适合于条件非常多的逻辑
eY`z\I 请看上述语句可以混合使用,请看
下载例子