全新java初学者实践教程6(Java SE5.0版)
~d*(=G 基本语法3
!s?nJ(p !6>~?gNd Hm'=aff6A 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:
\WB<86+z =\:qo'l [font="Times] 1.循环语句[font="Times]:while,do-while,for
s?,Ek 4s{~r [font="Times]2.分支语句[font="Times]:if-else,switch,
.j<]mUY [font="Times]
"v({, 3.跳转语句[font="Times] break,continue,label: 和[font="Times]return
~=RT*>G_ [font="Times]
@x'"~"%7b 4.异常处理语句[font="Times]:try-catch-finally,throw
OCaq3_#tZ TOXfWEU3> 实践:
e)#J1(j_ [font="Times] 1.循环语句
c*L\_Vx+ [font="Times] while 语句
8~z~_TD6m@ [font="Times]class While {
6){]1h" [font="Times]public static void main(String args[]) {
e-#BDN(O [font="Times]int n = 10;
nWYN Np?h [font="Times]while(n > 0) {
QD*35Y!d [font="Times]System.out.println("tick " + n);
[dIXR [font="Times]n--;
!1 8clL [font="Times]}
ll.N^y;a [font="Times]}
Jx7C'~,J [font="Times]}
H0`]V6+<f [font="Times] do…while 语句
}"PU%+J [font="Times] class DoWhile {
8sTp`}54J [font="Times]public static void main(String args[]) {
9V@V6TvW>& [font="Times]int n = 10;
ZE=Sp=@)j [font="Times]do {
K<qk.~
S [font="Times]System.out.println("tick " + n);
+:!7L=N# [font="Times]n--;
q[W
0 N> [font="Times]} while(n > 0);
Q&=w_Wc [font="Times]}
4V i`* ! [font="Times]}
1A G<$d5U| 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。
$ig0j` [font="Times] for语句
D" rK( [font="Times] class ForTick {
T)TfB( [font="Times]public static void main(String args[]) {
8xV9.4S [font="Times]int n;
$r8 ^0ZRr [font="Times]for(n=10; n>0; n--)
QoIT*! [font="Times]System.out.println("tick " + n);
vyX\'r.~7 [font="Times]}
r6}
|hpJ8 [font="Times]}
Q)"Nu.m
& 与上面那两个的区别,[font="Times]for循环执行的次数是可以在执行之前确定的。通俗一点说吧,看这个例子[font="Times] for(n=10; n>0; n--)就是在括号里的时候,就已经知道要循环[font="Times]10次了。
@As[k2 还有啊,[font="Times]for循环的部分可以为空的
c[4i9I3v [font="Times]class ForVar {
`e|0g"oP [font="Times]public static void main(String args[]) {
<[\`qX [font="Times]int i;
v|%Z+w [font="Times]boolean done = false;
'~[d=fwH [font="Times]i = 0;
kG@@ot" n [font="Times]for( ; !done; ) {
*|>d [font="Times]System.out.println("i is " + i);
dDGgvi|[Mz [font="Times]if(i == 10) done = true;
jW3!6*93 [font="Times]i++;
Xr$J9*Jk- [font="Times]}
u:gN?O/G [font="Times]}
9-
YwkK#z [font="Times]}
循环语句的例子下载 MmnOHN@. [font="Times] 2.分支语句[font="Times]
J|kR5'?x [font="Times] if/else语句
()Y4v [font="Times]class IfElse {
TKY*`?ct [font="Times]public static void main(String args[]) {
wKYZa# u [font="Times]int month = 4; // April
KB`!Sj\ [font="Times]String season;
q6SXWT'Sa [font="Times]if(month == 12 || month == 1 || month == 2)
NS%xTLow- [font="Times]season = "Winter";
I E&!YP(U( [font="Times]else if(month == 3 || month == 4 || month == 5)
Vp*KfS] [font="Times]season = "Spring";
v99B7VH4 [font="Times]else if(month == 6 || month == 7 || month == 8)
uRRQyZ [font="Times]season = "Summer";
`V]5 sE]G [font="Times]else if(month == 9 || month == 10 || month == 11)
bE#,=OI$ [font="Times]season = "Autumn";
zHL@i0>^ [font="Times]else
ICs\
z [font="Times]season = "Bogus Month";
%g$V\zmU [font="Times]System.out.println("April is in the " + season + ".");
!^=*Jq> [font="Times]}
,dov<U[ia [font="Times]}
(-xS?8x$ [font="Times]//这段程序输出[font="Times]:
1[qLA!+ [font="Times]//April is in the Spring.
Xti[[s J [font="Times]// 注意[font="Times] “[font="Times]||”是或运算
E^lvbLh' [font="Times] switch语句
Wm"4Ae:B [font="Times] class Switch {
+ SFVv_n [font="Times]public static void main(String args[]) {
I)cFG{~L [font="Times]int month = 4;
Hh-+/sO~" [font="Times]String season;
%?uc><&?e [font="Times]switch (month) {
;WM"cJo9 [font="Times]case 12:
$Ifmc`r1 [font="Times]case 1:
- UdEeZz. [font="Times]case 2:
`U)hjQ~pP [font="Times]season = "Winter";
"B4;,+4kR [font="Times]break;
2`>T oWN! [font="Times]case 3:
9{}1r2xW [font="Times]case 4:
wEE\+3b) [font="Times]case 5:
*:t|qgJI#+ [font="Times]season = "Spring";
p|jV{P [font="Times]break;
RwPN gRF [font="Times]case 6:
&8>IeK{I [font="Times]case 7:
)XakJU^o [font="Times]case 8:
%Nhx;{ [font="Times]season = "Summer";
,TPISs [font="Times]break;
g[Ib,la_a [font="Times]case 9:
L %K\C [font="Times]case 10:
c^u"I'#Q [font="Times]case 11:
/X(t1 + [font="Times]season = "Autumn";
8X`tU<Ab [font="Times]break;
pr#z=vqH [font="Times]default:
WObvbaK [font="Times]season = "Bogus Month";
Vf'd*-_!Q< [font="Times]}
Jd(,/q [font="Times]System.out.println("April is in the " + season + ".");
|8=nL$u [font="Times]}
,:`4% [font="Times]}
分支语句代码下载 ]Nl=wZ#` 2viM)+ [font="Times]switch语句适合于条件非常多的逻辑
:Jy'#c 请看上述语句可以混合使用,请看
下载例子