全新java初学者实践教程6(Java SE5.0版)
Wxjk}&+pVa 基本语法3
PX?tD:,[- iFF/[P y3 LWh}~E 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:
) OZDq]mV 5iG|C ~ [font="Times] 1.循环语句[font="Times]:while,do-while,for
&4O"Xs`ka BR*""/3` [font="Times]2.分支语句[font="Times]:if-else,switch,
@`%.\_ [font="Times]
`gfK#0x# 3.跳转语句[font="Times] break,continue,label: 和[font="Times]return
5c{=/}Y [font="Times]
twf;{lZ( 4.异常处理语句[font="Times]:try-catch-finally,throw
66:|) M[<O]p6 实践:
hh+GW*'~ [font="Times] 1.循环语句
DSd 5? [font="Times] while 语句
Y
+HVn0~qz [font="Times]class While {
WVy"MD [font="Times]public static void main(String args[]) {
dam.D.o" [font="Times]int n = 10;
3i>$g3G [font="Times]while(n > 0) {
FE M_7M [font="Times]System.out.println("tick " + n);
LFen!FnM [font="Times]n--;
{:4); . [font="Times]}
xS,):R [font="Times]}
_32ltnBX [font="Times]}
lba*&j]w= [font="Times] do…while 语句
b.YQN' [font="Times] class DoWhile {
:w:5;cmV [font="Times]public static void main(String args[]) {
F
b`V. [font="Times]int n = 10;
OX8jCW [font="Times]do {
7T4rx53 [font="Times]System.out.println("tick " + n);
1;? L:A [font="Times]n--;
7:bqh$3!s [font="Times]} while(n > 0);
V X211U.Q [font="Times]}
eHqf3f
[font="Times]}
^,U&v; 二者区别,[font="Times]do…while至少循环一次,而[font="Times]while的表达式要是为[font="Times]flase的话可以一次也不循环。再通俗一点,[font="Times]do…while就算是括号里的是[font="Times]flase,人家最少也能[font="Times]do一次。
JN|<R%hy [font="Times] for语句
gMHH3^\VH) [font="Times] class ForTick {
<@JU0Z"a= [font="Times]public static void main(String args[]) {
c^Wm~"r [font="Times]int n;
Hsp|<;Yg [font="Times]for(n=10; n>0; n--)
;R2(Gb [font="Times]System.out.println("tick " + n);
I]I5!\\ &[ [font="Times]}
fF-V=Zf5 [font="Times]}
!p0FJ].g, 与上面那两个的区别,[font="Times]for循环执行的次数是可以在执行之前确定的。通俗一点说吧,看这个例子[font="Times] for(n=10; n>0; n--)就是在括号里的时候,就已经知道要循环[font="Times]10次了。
WY*}|R2R 还有啊,[font="Times]for循环的部分可以为空的
BOh&Db* [font="Times]class ForVar {
&<tji8Dj [font="Times]public static void main(String args[]) {
+XY}- [font="Times]int i;
Kl+*Sp! [font="Times]boolean done = false;
&1w,;45 [font="Times]i = 0;
?I7H ): [font="Times]for( ; !done; ) {
@B&hR} 4 [font="Times]System.out.println("i is " + i);
#jDO?Y Sa [font="Times]if(i == 10) done = true;
WZFV8' [font="Times]i++;
\>YXPMIk [font="Times]}
NugJjd56x [font="Times]}
f5sk,Z [font="Times]}
循环语句的例子下载 t%FS 5 [font="Times] 2.分支语句[font="Times]
m m`:ci [font="Times] if/else语句
dFFB\|e;0 [font="Times]class IfElse {
{p2%4 [font="Times]public static void main(String args[]) {
9k$uo_i' [font="Times]int month = 4; // April
+A:}5{ [font="Times]String season;
E)Hp. [font="Times]if(month == 12 || month == 1 || month == 2)
kkd<CEz2IM [font="Times]season = "Winter";
sZB$+~.:} [font="Times]else if(month == 3 || month == 4 || month == 5)
W?6RUyMC$T [font="Times]season = "Spring";
?cpID8Z [font="Times]else if(month == 6 || month == 7 || month == 8)
<m )@~s?D [font="Times]season = "Summer";
<Ft.{aNq$c [font="Times]else if(month == 9 || month == 10 || month == 11)
JH?[hb [font="Times]season = "Autumn";
L[O+9Yh [font="Times]else
,u\M7,a^ [font="Times]season = "Bogus Month";
.@[+05Yw [font="Times]System.out.println("April is in the " + season + ".");
kM9E)uT>(< [font="Times]}
Y$,]~Qzq [font="Times]}
&}P62& [font="Times]//这段程序输出[font="Times]:
uvm=i . [font="Times]//April is in the Spring.
hVR=g!e#X [font="Times]// 注意[font="Times] “[font="Times]||”是或运算
VqYe0-^=P [font="Times] switch语句
43P?f+IYrk [font="Times] class Switch {
^M,Q<HL [font="Times]public static void main(String args[]) {
8ALYih7"W [font="Times]int month = 4;
"}ZD-O`! [font="Times]String season;
l(<o,Uv[` [font="Times]switch (month) {
IS8ppu&E [font="Times]case 12:
F%< 0pi [font="Times]case 1:
2I#fwsb [font="Times]case 2:
yfaXScbE [font="Times]season = "Winter";
~rKo5#D [font="Times]break;
AQ-PY [font="Times]case 3:
f PDnkr [font="Times]case 4:
i[FBll- [font="Times]case 5:
JEBx|U$'Y [font="Times]season = "Spring";
ogQbST [font="Times]break;
M)-+j{< [font="Times]case 6:
RL>[t [font="Times]case 7:
GJH6b7I [font="Times]case 8:
r,0> 40^ [font="Times]season = "Summer";
r5r K> [font="Times]break;
$XaZqzeVI [font="Times]case 9:
O":x$>'t [font="Times]case 10:
i12iB+q [font="Times]case 11:
%n{E/06f [font="Times]season = "Autumn";
]Nm_<%lT [font="Times]break;
7';PI!$ [font="Times]default:
JLs7[W)O [font="Times]season = "Bogus Month";
OyTBgS G?a [font="Times]}
3Vt-]DGX [font="Times]System.out.println("April is in the " + season + ".");
PUucYc [font="Times]}
A$%%;O [font="Times]}
分支语句代码下载 44b'40 8$@gAlI^ [font="Times]switch语句适合于条件非常多的逻辑
Imi_}NB+ 请看上述语句可以混合使用,请看
下载例子