全新java初学者实践教程6(Java SE5.0版)
L"AZ,|wIk 基本语法3
%POoyH@D} R7vO,kZ6Q kMUjSa~\ 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:
/Wt<[g# A_CK,S*\,& [font="Times] 1.循环语句[font="Times]:while,do-while,for
rR/PnVup c$>Tfa'H [font="Times]2.分支语句[font="Times]:if-else,switch,
O[$&]>x]] [font="Times]
8E|S`I 3.跳转语句[font="Times] break,continue,label: 和[font="Times]return
,%Dn}mWu [font="Times]
+Ge-!&.;A 4.异常处理语句[font="Times]:try-catch-finally,throw
)y._]is)b x%0Q W 实践:
40mgB4I [font="Times] 1.循环语句
zU]95I [font="Times] while 语句
)/Ul"QF [font="Times]class While {
c\7~_w2 [font="Times]public static void main(String args[]) {
0*x [font="Times]int n = 10;
3PPN_Z [font="Times]while(n > 0) {
g&&5F>mF [font="Times]System.out.println("tick " + n);
{8'I+- [font="Times]n--;
iFpJ/L [font="Times]}
.]P@{T||Y [font="Times]}
}ufH![|[r [font="Times]}
rtC.!].;% [font="Times] do…while 语句
iE>T5XV8$B [font="Times] class DoWhile {
TTu<~GH [font="Times]public static void main(String args[]) {
!@5B:n* [font="Times]int n = 10;
EE-jU<>| [font="Times]do {
]Z6==+mCP [font="Times]System.out.println("tick " + n);
E{|j [font="Times]n--;
usX
aT(K [font="Times]} while(n > 0);
F~4oPB K< [font="Times]}
:Fu.S1j$ [font="Times]}
O\8_;Gc; 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。
WF`y j%0 [font="Times] for语句
bZz ,' [font="Times] class ForTick {
Qn6'E [font="Times]public static void main(String args[]) {
i#=s_v8 [font="Times]int n;
O6 bB CF; [font="Times]for(n=10; n>0; n--)
%,1bh [font="Times]System.out.println("tick " + n);
=UT*1-yhR [font="Times]}
d%8hWlffz [font="Times]}
0escp~\Z 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。
!-)Hog5\ 还有啊,[font="Times]for循环的部分可以为空的
9+_SG/@ [font="Times]class ForVar {
-ich N/U]s [font="Times]public static void main(String args[]) {
gWL'Fl}H [font="Times]int i;
$0=f9+@5 [font="Times]boolean done = false;
Z2!O)8 [font="Times]i = 0;
wgp{P>oBX [font="Times]for( ; !done; ) {
9Eu.Y [font="Times]System.out.println("i is " + i);
5Ay\s:hb[u [font="Times]if(i == 10) done = true;
=*_T;;E [font="Times]i++;
GB&<+5t2 [font="Times]}
aOIE9wO [font="Times]}
^U)xQD" [font="Times]}
循环语句的例子下载 wak_^8x [font="Times] 2.分支语句[font="Times]
Pm*FA8 a7 [font="Times] if/else语句
s8Bbet [font="Times]class IfElse {
h0_od/D1r [font="Times]public static void main(String args[]) {
oF7o"NHaWa [font="Times]int month = 4; // April
,*!HN
& [font="Times]String season;
S&^i*R4] [font="Times]if(month == 12 || month == 1 || month == 2)
Xz4T_-X8d [font="Times]season = "Winter";
E>NRC\^@ [font="Times]else if(month == 3 || month == 4 || month == 5)
Ahv %Q%m%2 [font="Times]season = "Spring";
g
67;O(3 [font="Times]else if(month == 6 || month == 7 || month == 8)
~|QhWgq [font="Times]season = "Summer";
Wo+fMn(O [font="Times]else if(month == 9 || month == 10 || month == 11)
sba+J:#w [font="Times]season = "Autumn";
/?C}PM [font="Times]else
)\ow/XPE [font="Times]season = "Bogus Month";
|L%}@e
Vw_ [font="Times]System.out.println("April is in the " + season + ".");
`v)
:|Q [font="Times]}
B ~xT:r [font="Times]}
js^+ {~ [font="Times]//这段程序输出[font="Times]:
DPqk~ KCM [font="Times]//April is in the Spring.
K8,Q^!5]" [font="Times]// 注意[font="Times] “[font="Times]||”是或运算
.ww~'5b0 [font="Times] switch语句
3g
ep_aC [font="Times] class Switch {
,aq0Q<}~lc [font="Times]public static void main(String args[]) {
^/b3_aM5d [font="Times]int month = 4;
'~{bq'7`m [font="Times]String season;
M ^S <G [font="Times]switch (month) {
:rR)rj' [font="Times]case 12:
v!~tX*q [font="Times]case 1:
AYb-BaIc [font="Times]case 2:
a/p}
?!\ [font="Times]season = "Winter";
}JPLhr|d^ [font="Times]break;
gn,D9d+ [font="Times]case 3:
&BxDS
. [font="Times]case 4:
p$.m=+K~ [font="Times]case 5:
_/xA5/V [font="Times]season = "Spring";
awu18(;J [font="Times]break;
7\.{O$Q [font="Times]case 6:
hc#Sy:T> [font="Times]case 7:
&p