全新java初学者实践教程6(Java SE5.0版)
`Iqh\oY8- 基本语法3
^:u-wr8?{ Ial"nV0>0 P\ia ?9 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:
{%+UQ!]d8 QX+Xi<YE- [font="Times] 1.循环语句[font="Times]:while,do-while,for
Jq*Q;}n ' +f(9/ [font="Times]2.分支语句[font="Times]:if-else,switch,
fl}!V4 [font="Times]
:SD#>eD0 3.跳转语句[font="Times] break,continue,label: 和[font="Times]return
:ggXVwpe [font="Times]
}B ?_>0 4.异常处理语句[font="Times]:try-catch-finally,throw
-xVZm8y h7kn
>q; 实践:
3jx /1VV [font="Times] 1.循环语句
1$)}EL [font="Times] while 语句
SajasjE!^1 [font="Times]class While {
+n>p"+c [font="Times]public static void main(String args[]) {
QmC#1%@a [font="Times]int n = 10;
c+upoM [font="Times]while(n > 0) {
#+ Y%Bxf [font="Times]System.out.println("tick " + n);
Jbn^G7vH<6 [font="Times]n--;
kD
me>E= [font="Times]}
()W`4p [font="Times]}
0[f[6mm%m [font="Times]}
:?j]W2+kR [font="Times] do…while 语句
Jb6)U] [font="Times] class DoWhile {
wv [font="Times]public static void main(String args[]) {
1 T}jK^" [font="Times]int n = 10;
NpH9},1i [font="Times]do {
2 b80b50 [font="Times]System.out.println("tick " + n);
%)w7t[A2D [font="Times]n--;
AAF']z<4_" [font="Times]} while(n > 0);
*RmD%[f [font="Times]}
=wMq!mBd [font="Times]}
/5X_gjOL, 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。
NQcNY= [font="Times] for语句
`Y3\R# [font="Times] class ForTick {
QIfP%,LT [font="Times]public static void main(String args[]) {
x^Zm:Jrw~ [font="Times]int n;
jN!VrRA [font="Times]for(n=10; n>0; n--)
jdkqJ4&i [font="Times]System.out.println("tick " + n);
%6la@i [font="Times]}
u
s8.nL/ [font="Times]}
\olY)b[ 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。
oDWNOw 还有啊,[font="Times]for循环的部分可以为空的
.I]EP- [font="Times]class ForVar {
JfRLqA/ [font="Times]public static void main(String args[]) {
?DE{4Ti/[ [font="Times]int i;
akG|ic-~ [font="Times]boolean done = false;
p]qz+Z/ [font="Times]i = 0;
!ScEA= [font="Times]for( ; !done; ) {
p}e| E! [font="Times]System.out.println("i is " + i);
1'H!S%fS [font="Times]if(i == 10) done = true;
X/Ii}X/p [font="Times]i++;
qIxe)+. [font="Times]}
.O SQ8W} [font="Times]}
IP^1ca#< [font="Times]}
循环语句的例子下载 5cb8=W- [font="Times] 2.分支语句[font="Times]
b3ys"Vyn [font="Times] if/else语句
Z>~7|vl [font="Times]class IfElse {
:1;"{=Yx} [font="Times]public static void main(String args[]) {
p!EG:B4 [font="Times]int month = 4; // April
Z=
=c3~ [font="Times]String season;
yZ)-=H [font="Times]if(month == 12 || month == 1 || month == 2)
l=L(pS3 ~ [font="Times]season = "Winter";
2Vs+8/ [font="Times]else if(month == 3 || month == 4 || month == 5)
o1k+dJUd [font="Times]season = "Spring";
Z4g<Ys* [font="Times]else if(month == 6 || month == 7 || month == 8)
xwj{4fzpk{ [font="Times]season = "Summer";
`)>}b 3 [font="Times]else if(month == 9 || month == 10 || month == 11)
$h[Q}uW [font="Times]season = "Autumn";
iI;np+uYk [font="Times]else
hW` o-' [font="Times]season = "Bogus Month";
_p?s[r* [font="Times]System.out.println("April is in the " + season + ".");
;M"[dy`dY [font="Times]}
rH'|$~a [font="Times]}
B>[myx [font="Times]//这段程序输出[font="Times]:
^\r{72!y [font="Times]//April is in the Spring.
ANfy+@ [font="Times]// 注意[font="Times] “[font="Times]||”是或运算
wRZS+^hx [font="Times] switch语句
_YN
C}PUU [font="Times] class Switch {
g9Ty%|Q7( [font="Times]public static void main(String args[]) {
c<sq0('` [font="Times]int month = 4;
xEv?2n@A [font="Times]String season;
`NNP}O2 [font="Times]switch (month) {
=}0$|@pl [font="Times]case 12:
1@9M[_<n5 [font="Times]case 1:
X`fm5y [font="Times]case 2:
tBETNt7 [font="Times]season = "Winter";
Ap 3B' [font="Times]break;
Qn.3B [font="Times]case 3:
^>^h|$ [font="Times]case 4:
"N)InPR- [font="Times]case 5:
cqT%6Si [font="Times]season = "Spring";
^])s\a$ [font="Times]break;
\odns [font="Times]case 6:
0<##8m@F8 [font="Times]case 7:
'Er\68 [font="Times]case 8:
wh!8\9{g [font="Times]season = "Summer";
KL*+gq0k [font="Times]break;
cC]]H&'Hg+ [font="Times]case 9:
(hh^? [font="Times]case 10:
AmQsay#I_ [font="Times]case 11:
P<;Puww/ [font="Times]season = "Autumn";
Wz#ZkNO [font="Times]break;
g`~;"%u7cn [font="Times]default:
2wa'WEx [font="Times]season = "Bogus Month";
bP,Ka [font="Times]}
>qUD_U3A [font="Times]System.out.println("April is in the " + season + ".");
1tTY)Evf [font="Times]}
CAmIwAx6; [font="Times]}
分支语句代码下载 ff=RKKnN k5*Z@a [font="Times]switch语句适合于条件非常多的逻辑
A|GsbRuy 请看上述语句可以混合使用,请看
下载例子