全新java初学者实践教程6(Java SE5.0版)
ttP|}|O 基本语法3
D02'P{ YCPU84f wH?]kV8Q 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:
SEKR`2Zz, LZ=E [font="Times] 1.循环语句[font="Times]:while,do-while,for
NqlU? /Fr*k5I [font="Times]2.分支语句[font="Times]:if-else,switch,
Ez1-Nx [font="Times]
ylGT9G19 3.跳转语句[font="Times] break,continue,label: 和[font="Times]return
?^3Y+)} [font="Times]
14~#k%zO( 4.异常处理语句[font="Times]:try-catch-finally,throw
FhP$R}F AU$<W"%R 实践:
&0b\E73 [font="Times] 1.循环语句
pyw]ydB [font="Times] while 语句
(G6lr%d [font="Times]class While {
V7 OhOLK8 [font="Times]public static void main(String args[]) {
\sn
wR [font="Times]int n = 10;
O#_\@f#[ [font="Times]while(n > 0) {
c9ye[81 [font="Times]System.out.println("tick " + n);
ge#0Q L0K [font="Times]n--;
/4I9Elr [font="Times]}
"F[e~S#V* [font="Times]}
#x+7-hi [font="Times]}
`uwSxt [font="Times] do…while 语句
=L\&}kzB [font="Times] class DoWhile {
Kj7
?_o{ [font="Times]public static void main(String args[]) {
ul-O3]\'@ [font="Times]int n = 10;
/$\N_`bM [font="Times]do {
/Moyn"Kj{ [font="Times]System.out.println("tick " + n);
v) j3YhY [font="Times]n--;
H'"=C&D~ [font="Times]} while(n > 0);
Hg~8Td** [font="Times]}
>qy$W4 [font="Times]}
\b;z$P\+* 二者区别,[font="Times]do…while至少循环一次,而[font="Times]while的表达式要是为[font="Times]flase的话可以一次也不循环。再通俗一点,[font="Times]do…while就算是括号里的是[font="Times]flase,人家最少也能[font="Times]do一次。
qV#,]mX [font="Times] for语句
cy64xR BB [font="Times] class ForTick {
Qef5eih [font="Times]public static void main(String args[]) {
M7fPaJKL [font="Times]int n;
6vfut$)[{ [font="Times]for(n=10; n>0; n--)
{1"kZL [font="Times]System.out.println("tick " + n);
u0Bz]Ux/Q [font="Times]}
`t7z
LC^c [font="Times]}
w-"tA`F4 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。
F05]6NVv 还有啊,[font="Times]for循环的部分可以为空的
tjLG$M1z` [font="Times]class ForVar {
!ra,HkU' [font="Times]public static void main(String args[]) {
N0pA ,& [font="Times]int i;
;S9
z@`a. [font="Times]boolean done = false;
XZ=%XB:? [font="Times]i = 0;
M?00n< vM [font="Times]for( ; !done; ) {
n v
?u [font="Times]System.out.println("i is " + i);
=TGa\iclpB [font="Times]if(i == 10) done = true;
);/p[Fd2] [font="Times]i++;
e +Ikw1y"f [font="Times]}
*x/H [font="Times]}
+ovT?CMo [font="Times]}
循环语句的例子下载 R('\i/fy [font="Times] 2.分支语句[font="Times]
mwMc AUD]2 [font="Times] if/else语句
,`ba?O?*G [font="Times]class IfElse {
?>1wZ [font="Times]public static void main(String args[]) {
i'B$Xr [font="Times]int month = 4; // April
Ou_2UT [font="Times]String season;
Obx!>mI^6 [font="Times]if(month == 12 || month == 1 || month == 2)
@rv)J[7Y& [font="Times]season = "Winter";
q%/\ [font="Times]else if(month == 3 || month == 4 || month == 5)
8]i7wq#= [font="Times]season = "Spring";
v*kX?J#]5 [font="Times]else if(month == 6 || month == 7 || month == 8)
g;7W%v5wqk [font="Times]season = "Summer";
U
UhlKV|5 [font="Times]else if(month == 9 || month == 10 || month == 11)
D/ tCB-+ [font="Times]season = "Autumn";
G|I}x/X"Q7 [font="Times]else
BZa`:ah~x [font="Times]season = "Bogus Month";
pwvmb\ [font="Times]System.out.println("April is in the " + season + ".");
,z01*Yx [font="Times]}
x21XzGLY|} [font="Times]}
GMY[Gd [font="Times]//这段程序输出[font="Times]:
<Zo{D |hW [font="Times]//April is in the Spring.
n0FzDQt26 [font="Times]// 注意[font="Times] “[font="Times]||”是或运算
><C9PS@ [font="Times] switch语句
;>%wf3e [font="Times] class Switch {
gSHN,8.
` [font="Times]public static void main(String args[]) {
,:{+-v( [font="Times]int month = 4;
mLV0J ' [font="Times]String season;
(~NR."s; [font="Times]switch (month) {
OD~yIV [font="Times]case 12:
dn&484 [font="Times]case 1:
oT!i}TW?o [font="Times]case 2:
3fUiYI|&7 [font="Times]season = "Winter";
3U!
l8N2 [font="Times]break;
y\n#`*5k [font="Times]case 3:
"[sr0'g: [font="Times]case 4:
vs{VRc [font="Times]case 5:
dtBr#Te [font="Times]season = "Spring";
fRwr}n' [font="Times]break;
XaaR>HljJ [font="Times]case 6:
Rw<O%i5/d [font="Times]case 7:
.7+"KP: [font="Times]case 8:
'(zP; [font="Times]season = "Summer";
09=w [font="Times]break;
_U
o3_us [font="Times]case 9:
w^ X@PpP [font="Times]case 10:
/vPr^Wv [font="Times]case 11:
^SbxClUfw! [font="Times]season = "Autumn";
s)+] pxV0- [font="Times]break;
e35 ")z~ [font="Times]default:
%NcBq3 [font="Times]season = "Bogus Month";
braI MIQ` [font="Times]}
j>5X^Jd [font="Times]System.out.println("April is in the " + season + ".");
%v0;1m [font="Times]}
L lD=c [font="Times]}
分支语句代码下载 xg4wtfAbS )Wk&c8|y [font="Times]switch语句适合于条件非常多的逻辑
?weuq"*a 请看上述语句可以混合使用,请看
下载例子