全新java初学者实践教程6(Java SE5.0版)
TKB8%/_p 基本语法3
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WB" 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:
qp})4XT v &-=~8 [font="Times] 1.循环语句[font="Times]:while,do-while,for
I3Vu/&8f| Cqr{Nssu [font="Times]2.分支语句[font="Times]:if-else,switch,
ojM'8z0Hn [font="Times]
32ki ?\P 3.跳转语句[font="Times] break,continue,label: 和[font="Times]return
^~~Rto)Y [font="Times]
wA5Iz{uQO 4.异常处理语句[font="Times]:try-catch-finally,throw
w-K A~ eFiG:LS7 实践:
X:i?gRy" [font="Times] 1.循环语句
cW%)C.M [font="Times] while 语句
[G}dPXD [font="Times]class While {
#]}Ii{1?Y [font="Times]public static void main(String args[]) {
~B;}jI]d[ [font="Times]int n = 10;
05wkUo:9 [font="Times]while(n > 0) {
v@\S$qU2 [font="Times]System.out.println("tick " + n);
$g>bp<9v4 [font="Times]n--;
t%qep| [font="Times]}
=yod [font="Times]}
^Q8yb*MN [font="Times]}
UR'[? [font="Times] do…while 语句
u@_|4Bp," [font="Times] class DoWhile {
M/o?D <' [font="Times]public static void main(String args[]) {
mjD^iu8? [font="Times]int n = 10;
_&-d0'+ [font="Times]do {
#}^waYAk) [font="Times]System.out.println("tick " + n);
v'hc-Q9+> [font="Times]n--;
0D,@^vw bK [font="Times]} while(n > 0);
v`|]57?A [font="Times]}
'zUV(K?2] [font="Times]}
|m's) 二者区别,[font="Times]do…while至少循环一次,而[font="Times]while的表达式要是为[font="Times]flase的话可以一次也不循环。再通俗一点,[font="Times]do…while就算是括号里的是[font="Times]flase,人家最少也能[font="Times]do一次。
OJe!K: [font="Times] for语句
]9YA~n\ [font="Times] class ForTick {
u>
{aF{ [font="Times]public static void main(String args[]) {
'yiv.<4 [font="Times]int n;
vkG#G]Qs"; [font="Times]for(n=10; n>0; n--)
E)*ht;u [font="Times]System.out.println("tick " + n);
&wQ;J)13 [font="Times]}
edL2ax [font="Times]}
!ZTghX}D 与上面那两个的区别,[font="Times]for循环执行的次数是可以在执行之前确定的。通俗一点说吧,看这个例子[font="Times] for(n=10; n>0; n--)就是在括号里的时候,就已经知道要循环[font="Times]10次了。
PNm@mC_fh 还有啊,[font="Times]for循环的部分可以为空的
|+Wn5iT [font="Times]class ForVar {
[ cB^6v [font="Times]public static void main(String args[]) {
H'WYnhU& [font="Times]int i;
/9_%NR[
[font="Times]boolean done = false;
l#[Z$+!09 [font="Times]i = 0;
(HRj0,/^ [font="Times]for( ; !done; ) {
beOMln+R [font="Times]System.out.println("i is " + i);
&PC6C<<f [font="Times]if(i == 10) done = true;
}d%CZnY&7 [font="Times]i++;
:?xH)J,imk [font="Times]}
/h53;$zK [font="Times]}
"l&SRX?g [font="Times]}
循环语句的例子下载 `rn/H;r!Z [font="Times] 2.分支语句[font="Times]
89M'klZ [font="Times] if/else语句
Q/|.=:~FO [font="Times]class IfElse {
m1W) PUy [font="Times]public static void main(String args[]) {
%,[,mW4l [font="Times]int month = 4; // April
Htgo=7!?\3 [font="Times]String season;
B{/og*xd*1 [font="Times]if(month == 12 || month == 1 || month == 2)
a"@f< wU~ [font="Times]season = "Winter";
0Md>-H;ZY [font="Times]else if(month == 3 || month == 4 || month == 5)
()aCE^C [font="Times]season = "Spring";
U`6|K$@ [font="Times]else if(month == 6 || month == 7 || month == 8)
O:0{vu9AQ [font="Times]season = "Summer";
bSe\d~{ [font="Times]else if(month == 9 || month == 10 || month == 11)
w+6P x# [font="Times]season = "Autumn";
!.UE} ^TV [font="Times]else
ST{Vi';} [font="Times]season = "Bogus Month";
*EuX7LEu_ [font="Times]System.out.println("April is in the " + season + ".");
l,o'J%<% [font="Times]}
dfFw6R [font="Times]}
c'Z=uL<Rm [font="Times]//这段程序输出[font="Times]:
WWpMuB_G [font="Times]//April is in the Spring.
%_|KiW [font="Times]// 注意[font="Times] “[font="Times]||”是或运算
Hhtl~2t!0 [font="Times] switch语句
y[b8rv [font="Times] class Switch {
Q"I(3 tp9[ [font="Times]public static void main(String args[]) {
bUcp8 [font="Times]int month = 4;
`}ak]Z_ [font="Times]String season;
,=+t2Bn [font="Times]switch (month) {
v?."`,e [font="Times]case 12:
V0^{Ss1M [font="Times]case 1:
C+'-TLeu [font="Times]case 2:
%Yu~56c- [font="Times]season = "Winter";
(7qlp*8.s [font="Times]break;
nXn@|J&z~U [font="Times]case 3:
3(oMASf [font="Times]case 4:
qWH^/o [font="Times]case 5:
i(%2t(wf+ [font="Times]season = "Spring";
1
*'
/B [font="Times]break;
g|Lbe4? [font="Times]case 6:
bll[E}E|3 [font="Times]case 7:
*)RKU),3nL [font="Times]case 8:
>N#Nz
0|( [font="Times]season = "Summer";
g**!'T4&o [font="Times]break;
MFROAVPZ5 [font="Times]case 9:
#e@NV4q [font="Times]case 10:
#QFz /6 [font="Times]case 11:
_;3, [font="Times]season = "Autumn";
pFH.beY [font="Times]break;
93*d:W8Vr [font="Times]default:
JtO}i{A [font="Times]season = "Bogus Month";
E_~e/y"- [font="Times]}
CT'4. [font="Times]System.out.println("April is in the " + season + ".");
'9!_:3[d\] [font="Times]}
0J+WCm` [font="Times]}
分支语句代码下载 S${%T$> :fj>JF\[ [font="Times]switch语句适合于条件非常多的逻辑
vD8pVR+ 请看上述语句可以混合使用,请看
下载例子