全新java初学者实践教程6(Java SE5.0版)
W|h~&O 基本语法3
sh;DCd 1c8Nr&Jl E#}OIZ\S 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:
#0>??]&r g<U\7Vp\1 [font="Times] 1.循环语句[font="Times]:while,do-while,for
NU[{ANbl '/M9V{DD88 [font="Times]2.分支语句[font="Times]:if-else,switch,
Wd"<u2 [font="Times]
l7#5.%A 3.跳转语句[font="Times] break,continue,label: 和[font="Times]return
IlN: NS [font="Times]
#$W02L8 4.异常处理语句[font="Times]:try-catch-finally,throw
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BV)oF2b: 实践:
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[font="Times] 1.循环语句
y0s=yN_ [font="Times] while 语句
X)7_@,7 [font="Times]class While {
kq|(t{@Rp [font="Times]public static void main(String args[]) {
:Ywb [font="Times]int n = 10;
8LuM eGs
[font="Times]while(n > 0) {
>}<1 [font="Times]System.out.println("tick " + n);
SFqY*:svOw [font="Times]n--;
8R|!$P [font="Times]}
h; " 9. [font="Times]}
C\2 rSyo [font="Times]}
j=|cx+nb [font="Times] do…while 语句
MXQua:&HW [font="Times] class DoWhile {
wNc.z*+O"H [font="Times]public static void main(String args[]) {
xs#g [font="Times]int n = 10;
>^Rkk{cc [font="Times]do {
,GOH8h [font="Times]System.out.println("tick " + n);
EPeKg{w [font="Times]n--;
($QQuM= [font="Times]} while(n > 0);
RZMR2fP% [font="Times]}
I;xSd.- [font="Times]}
{:=sCY! 二者区别,[font="Times]do…while至少循环一次,而[font="Times]while的表达式要是为[font="Times]flase的话可以一次也不循环。再通俗一点,[font="Times]do…while就算是括号里的是[font="Times]flase,人家最少也能[font="Times]do一次。
[}>!$::Y [font="Times] for语句
\dAs<${( [font="Times] class ForTick {
suOWmqLs [font="Times]public static void main(String args[]) {
,bTpD! [font="Times]int n;
/3Y\s&y [font="Times]for(n=10; n>0; n--)
|k.%e4 [font="Times]System.out.println("tick " + n);
'Fq+\J#% [font="Times]}
_(7f0p [font="Times]}
iYaS 与上面那两个的区别,[font="Times]for循环执行的次数是可以在执行之前确定的。通俗一点说吧,看这个例子[font="Times] for(n=10; n>0; n--)就是在括号里的时候,就已经知道要循环[font="Times]10次了。
*Wj]e% 还有啊,[font="Times]for循环的部分可以为空的
N!~O~Eo3 [font="Times]class ForVar {
zSd!n [font="Times]public static void main(String args[]) {
Ww=^P{q\ [font="Times]int i;
Gxh r0' [font="Times]boolean done = false;
N 2XL5< [font="Times]i = 0;
4og/y0n,l" [font="Times]for( ; !done; ) {
JjMa [font="Times]System.out.println("i is " + i);
i}Q"'? [font="Times]if(i == 10) done = true;
W6c]a/ [font="Times]i++;
njxfBA: [font="Times]}
9{*$[%d1 [font="Times]}
)kMF~S|H [font="Times]}
循环语句的例子下载 sP:nTpTsC [font="Times] 2.分支语句[font="Times]
Cer&VMrQK [font="Times] if/else语句
<%4M\n [font="Times]class IfElse {
mNA=<O;i)' [font="Times]public static void main(String args[]) {
;yu#Bs [font="Times]int month = 4; // April
=;Q:z^S [font="Times]String season;
3xIelTf* [font="Times]if(month == 12 || month == 1 || month == 2)
/7N&4FrG [font="Times]season = "Winter";
}3O 0nab [font="Times]else if(month == 3 || month == 4 || month == 5)
qdnwaJ;& [font="Times]season = "Spring";
{gz-w|7 [font="Times]else if(month == 6 || month == 7 || month == 8)
2A=q{7s [font="Times]season = "Summer";
]?G|:Kx$y% [font="Times]else if(month == 9 || month == 10 || month == 11)
r'(*# [font="Times]season = "Autumn";
`92P~Y~`W [font="Times]else
c_4K [font="Times]season = "Bogus Month";
rnyXMt.q [font="Times]System.out.println("April is in the " + season + ".");
do.AesdXaq [font="Times]}
FUVp}>#U [font="Times]}
8IkmFXj [font="Times]//这段程序输出[font="Times]:
oRZ98?Y\B
[font="Times]//April is in the Spring.
"wy2u~ [font="Times]// 注意[font="Times] “[font="Times]||”是或运算
j:2TicHDC [font="Times] switch语句
s_;o1 K0 [font="Times] class Switch {
k{F]^VXQ [font="Times]public static void main(String args[]) {
5,R4:y ?cK [font="Times]int month = 4;
?}e^-//*i [font="Times]String season;
Kn=0AdM [font="Times]switch (month) {
w,i?e\5 [font="Times]case 12:
=&i#NSK [font="Times]case 1:
i!{A7mo [font="Times]case 2:
s(T0lul [font="Times]season = "Winter";
!,|-{": [font="Times]break;
boq=@Qh [font="Times]case 3:
l6*MiX]q [font="Times]case 4:
]ZnASlc) [font="Times]case 5:
P$x9Z3d_ [font="Times]season = "Spring";
e9R H[: [font="Times]break;
'NMO>[. [font="Times]case 6:
O9P+S|hcY [font="Times]case 7:
Zg%tN#6y [font="Times]case 8:
HLkI?mW< [font="Times]season = "Summer";
p#%*z~ui [font="Times]break;
_\8jnpT: [font="Times]case 9:
'%X29B5 [font="Times]case 10:
>4#:qIU [font="Times]case 11:
#w3J+U 6r [font="Times]season = "Autumn";
< 1%}8t" [font="Times]break;
}Y^o("c(
[font="Times]default:
Q=61.lP6 [font="Times]season = "Bogus Month";
_N {4Rs0 [font="Times]}
%8H$62w] [font="Times]System.out.println("April is in the " + season + ".");
d6a3\f [font="Times]}
z/]]u.UP [font="Times]}
分支语句代码下载 $1$0M M1]}yTCd [font="Times]switch语句适合于条件非常多的逻辑
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L =&I 请看上述语句可以混合使用,请看
下载例子