全新java初学者实践教程6(Java SE5.0版)
B#3Q4c$ 基本语法3
dfh 1^Go yI/ FD Zh`[A9I/ 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:
beNy5~M$ ~y,m7%L [font="Times] 1.循环语句[font="Times]:while,do-while,for
x~](d8*= Vd'=Fe;eB [font="Times]2.分支语句[font="Times]:if-else,switch,
Xv+,Z<>iQ [font="Times]
QZuKM 'D+ 3.跳转语句[font="Times] break,continue,label: 和[font="Times]return
h05<1>?| [font="Times]
20I/En 4.异常处理语句[font="Times]:try-catch-finally,throw
e`Co =' Of}C.N8 实践:
RrdLh z2N [font="Times] 1.循环语句
OP\L [font="Times] while 语句
$oPc,zS-gL [font="Times]class While {
)4>7X)j> [font="Times]public static void main(String args[]) {
ARG8\qU [font="Times]int n = 10;
S 8)!70 [font="Times]while(n > 0) {
yI^7sf7k [font="Times]System.out.println("tick " + n);
R*2F)e\| [font="Times]n--;
.Ad9(s [font="Times]}
-lR7
@S [font="Times]}
{BgJ=0g? [font="Times]}
~.tYYX< [font="Times] do…while 语句
R@U4Ae{+ [font="Times] class DoWhile {
AJ)&+H [font="Times]public static void main(String args[]) {
;s -@m< [font="Times]int n = 10;
tq51;L [font="Times]do {
LjIkZ'HuF [font="Times]System.out.println("tick " + n);
D0>Pc9 [font="Times]n--;
:>F3es` [font="Times]} while(n > 0);
9TwKd0AT$& [font="Times]}
I1I-,~hO [font="Times]}
<kWkc|zBY 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。
*]nk{jo2 [font="Times] for语句
`>OKV;~{z [font="Times] class ForTick {
6Cfsh<]b [font="Times]public static void main(String args[]) {
%/qwqo`Q
[font="Times]int n;
z[y [font="Times]for(n=10; n>0; n--)
v8n^~=SH [font="Times]System.out.println("tick " + n);
amQTPNI [font="Times]}
n~ 0MhE0H [font="Times]}
=ADOf_n} 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。
ae](=OQ 还有啊,[font="Times]for循环的部分可以为空的
/Z[HU{4 [font="Times]class ForVar {
ce; zn\ [font="Times]public static void main(String args[]) {
lQy-&d|=#^ [font="Times]int i;
|kTq
&^$ [font="Times]boolean done = false;
W Bb*2 [font="Times]i = 0;
!Uv>>MCr [font="Times]for( ; !done; ) {
l]gW_wUQd [font="Times]System.out.println("i is " + i);
-!K&\hEjj [font="Times]if(i == 10) done = true;
k|{ 4"4r [font="Times]i++;
/_YTOSZjm [font="Times]}
y|zIuI-p [font="Times]}
H!>>|6OPF [font="Times]}
循环语句的例子下载 Z]x6np [font="Times] 2.分支语句[font="Times]
mI]gDL1 [font="Times] if/else语句
5"X@<;H% [font="Times]class IfElse {
%0Qq~J@Lu [font="Times]public static void main(String args[]) {
e1%kW1Z9 [font="Times]int month = 4; // April
%?Q&a ] [font="Times]String season;
9ExI, [font="Times]if(month == 12 || month == 1 || month == 2)
\L`x![$~q [font="Times]season = "Winter";
EY:H\4) [font="Times]else if(month == 3 || month == 4 || month == 5)
p}5413z5Z= [font="Times]season = "Spring";
SpYmgL?wJ [font="Times]else if(month == 6 || month == 7 || month == 8)
FZIC|uz [font="Times]season = "Summer";
N;k )> [font="Times]else if(month == 9 || month == 10 || month == 11)
<lLJf8OK [font="Times]season = "Autumn";
) .KMZ] [font="Times]else
sZ;Gb^{Z [font="Times]season = "Bogus Month";
USS%T<Vk [font="Times]System.out.println("April is in the " + season + ".");
X*:,| [font="Times]}
:8HVq*itS [font="Times]}
{m@tt{% [font="Times]//这段程序输出[font="Times]:
o8v,178 [font="Times]//April is in the Spring.
|~PaCw8-ge [font="Times]// 注意[font="Times] “[font="Times]||”是或运算
nF<xJs [font="Times] switch语句
\Hf/8!q [font="Times] class Switch {
`uZMln @ [font="Times]public static void main(String args[]) {
f1;@a>X
[font="Times]int month = 4;
OiS\tK?|GV [font="Times]String season;
Rjv;[ [font="Times]switch (month) {
4O/IT1+A [font="Times]case 12:
oZ ^,* [font="Times]case 1:
ect$g# [font="Times]case 2:
`S.I,<& [font="Times]season = "Winter";
B2a#:E,6 [font="Times]break;
/Ov1eQBNG [font="Times]case 3:
R/kJUl6HEl [font="Times]case 4:
/lh1sHgD [font="Times]case 5:
WtaOf_ [font="Times]season = "Spring";
`j!_tE` [font="Times]break;
y7%SHYC p[ [font="Times]case 6:
gVI`&W__, [font="Times]case 7:
~*9Ue@ [font="Times]case 8:
hJD3G
|E [font="Times]season = "Summer";
o)]O [font="Times]break;
B2'TRXIm1U [font="Times]case 9:
l2}X\N&q [font="Times]case 10:
|\/\FK]?] [font="Times]case 11:
=8%*Rrj^ [font="Times]season = "Autumn";
yn_. [font="Times]break;
iz{TSU [font="Times]default:
8FZC0j.^DH [font="Times]season = "Bogus Month";
Nu\<Xr8 [font="Times]}
kyt HOn# [font="Times]System.out.println("April is in the " + season + ".");
K=nDC. [font="Times]}
>tx[UF@P@ [font="Times]}
分支语句代码下载 ~8"oH5 S^|U" [font="Times]switch语句适合于条件非常多的逻辑
^FkB/j 请看上述语句可以混合使用,请看
下载例子