全新java初学者实践教程6(Java SE5.0版)
,n TC7V 基本语法3
%/b?T]{ frbKi _1 ZXljCiNn+\ 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:
01}az~&;35 <iunDL0 [font="Times] 1.循环语句[font="Times]:while,do-while,for
i%+cPQ^o 9V`/zq? [font="Times]2.分支语句[font="Times]:if-else,switch,
SLpB$puS [font="Times]
$r *7)/ 3.跳转语句[font="Times] break,continue,label: 和[font="Times]return
7kx)/Rw\B [font="Times]
csz/[* 4.异常处理语句[font="Times]:try-catch-finally,throw
HGfV2FtT z 0RAmwfXm 实践:
2MQgTFM9 [font="Times] 1.循环语句
&Z/aM? [font="Times] while 语句
!}|n3wQ [font="Times]class While {
xCFk1%qf [font="Times]public static void main(String args[]) {
%&5 !vK [font="Times]int n = 10;
4YM!S E-I [font="Times]while(n > 0) {
vg"y$% [font="Times]System.out.println("tick " + n);
``j..v, [font="Times]n--;
I>o+INb: [font="Times]}
a'U7 t [font="Times]}
=`[08 [font="Times]}
Wk"4mq [font="Times] do…while 语句
vBx*bZ [font="Times] class DoWhile {
rCi7q]_ [font="Times]public static void main(String args[]) {
8M*[RlUJB [font="Times]int n = 10;
~[dU%I>L^ [font="Times]do {
0'*whhH [font="Times]System.out.println("tick " + n);
{j@
S<PD [font="Times]n--;
Vd~{SS2> [font="Times]} while(n > 0);
]J+}WR [font="Times]}
/fbI4&SB! [font="Times]}
xZW6Hk_ 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。
4V9DPBh [font="Times] for语句
dOh'9kk3 [font="Times] class ForTick {
jOj`S%7 [font="Times]public static void main(String args[]) {
sE@t$'= [font="Times]int n;
N|K,{
p^li [font="Times]for(n=10; n>0; n--)
?rID fEvV [font="Times]System.out.println("tick " + n);
q+f]E&': [font="Times]}
rTYDa3 [font="Times]}
.|
CcUmx 与上面那两个的区别,[font="Times]for循环执行的次数是可以在执行之前确定的。通俗一点说吧,看这个例子[font="Times] for(n=10; n>0; n--)就是在括号里的时候,就已经知道要循环[font="Times]10次了。
_Qg^>}]A1 还有啊,[font="Times]for循环的部分可以为空的
Ab`mID: [font="Times]class ForVar {
UOHU1.3$T [font="Times]public static void main(String args[]) {
]Aap4+s [font="Times]int i;
p>4$&- [font="Times]boolean done = false;
ON#\W>MK? [font="Times]i = 0;
y%)5r}S^ [font="Times]for( ; !done; ) {
=<w6yeko [font="Times]System.out.println("i is " + i);
wJ@8-H 8} [font="Times]if(i == 10) done = true;
LW6&^S?4{ [font="Times]i++;
e@' rY#:u [font="Times]}
CY;ML6c@ [font="Times]}
G6K;3B [font="Times]}
循环语句的例子下载 (,1}P [font="Times] 2.分支语句[font="Times]
b:3n)-V{ u [font="Times] if/else语句
08AC9 [font="Times]class IfElse {
AujvKQ( [font="Times]public static void main(String args[]) {
sPY*2B [font="Times]int month = 4; // April
W$LaXytmak [font="Times]String season;
U;Z6o1G [font="Times]if(month == 12 || month == 1 || month == 2)
f"t\-ux.b [font="Times]season = "Winter";
{o"X8 [font="Times]else if(month == 3 || month == 4 || month == 5)
x)0g31 49 [font="Times]season = "Spring";
9t@^P^}=\m [font="Times]else if(month == 6 || month == 7 || month == 8)
q<`YJ, [font="Times]season = "Summer";
TxAT )) [font="Times]else if(month == 9 || month == 10 || month == 11)
&os9K) [font="Times]season = "Autumn";
92_F8y*D [font="Times]else
~01
o [font="Times]season = "Bogus Month";
TP' [font="Times]System.out.println("April is in the " + season + ".");
9n{tbabJ [font="Times]}
OJ8 ac6cJ [font="Times]}
!9=hUpRN [font="Times]//这段程序输出[font="Times]:
f1MKYM%^x [font="Times]//April is in the Spring.
=g4^tIYq [font="Times]// 注意[font="Times] “[font="Times]||”是或运算
"3o{@TdU [font="Times] switch语句
2?YN8
n9n [font="Times] class Switch {
N^7Qn*qt[ [font="Times]public static void main(String args[]) {
&No6k~T0:b [font="Times]int month = 4;
~$XbYR- [font="Times]String season;
N%N% [font="Times]switch (month) {
f!hQ"1[ [font="Times]case 12:
Sx)b~ * [font="Times]case 1:
$3>k/*= [font="Times]case 2:
^$qr6+ [font="Times]season = "Winter";
z-fP#. [font="Times]break;
lJ.:5$2H [font="Times]case 3:
%,f|H :+>u [font="Times]case 4:
lx*"Pj9hho [font="Times]case 5:
z{:T~s [font="Times]season = "Spring";
MGpP'G:v [font="Times]break;
?"f\"N [font="Times]case 6:
{^>dQ+S x7 [font="Times]case 7:
kKr|PFz [font="Times]case 8:
r&sm&4)p-5 [font="Times]season = "Summer";
t mAj [font="Times]break;
.;j} :< [font="Times]case 9:
ol]"r5#Q_H [font="Times]case 10:
0'y9HE'e [font="Times]case 11:
OB"Ur-hJ0 [font="Times]season = "Autumn";
55xaZ#| [font="Times]break;
zf-)c1$*r [font="Times]default:
lM
]n [font="Times]season = "Bogus Month";
Ny|2Fcs [font="Times]}
\49LgN@\ [font="Times]System.out.println("April is in the " + season + ".");
1L722I@ [font="Times]}
"@: b'm [font="Times]}
分支语句代码下载 USF&; M3 [1{#a {4 [font="Times]switch语句适合于条件非常多的逻辑
1_JtD|Jy 请看上述语句可以混合使用,请看
下载例子