全新java初学者实践教程6(Java SE5.0版)
sZ&|omN 基本语法3
$G"\@YC< (W:@v&p $RY GAh 我们这个教程侧重的是实践的内容和语言的重点。在[font="Times]java语言中还有很多细节的东西,请参考[font="Times]sun公司的官方培训教程。我们这里不能一一讲述。这节课我们来给大家提供一些程序流程控制的一些例子供大家学习。计算机怎么做事情,是我们教给他的。我们用它解决实际生活中的问题,所以计算机要描述现实生活中的流程。[font="Times]Java语言中提供了[font="Times]4类程序控制语句,来描述流程:
8YlZ({f HOWpTu( [font="Times] 1.循环语句[font="Times]:while,do-while,for
Fovah4q%V bs)wxU`Q* [font="Times]2.分支语句[font="Times]:if-else,switch,
\l/}` w [font="Times]
*|\bS " 3.跳转语句[font="Times] break,continue,label: 和[font="Times]return
bs~P [font="Times]
C@`#@1X 4.异常处理语句[font="Times]:try-catch-finally,throw
Icg-rwa<Z b,~pwbHf 实践:
^t
gjs$M| [font="Times] 1.循环语句
HSG Ln906 [font="Times] while 语句
H6 x [font="Times]class While {
T&pCLvkz [font="Times]public static void main(String args[]) {
oydP}X [font="Times]int n = 10;
=&UE67eK, [font="Times]while(n > 0) {
8HBwcXYoHh [font="Times]System.out.println("tick " + n);
IP#vfM [font="Times]n--;
TA*}p=?6?! [font="Times]}
]YhQQH1>] [font="Times]}
>_yL@^ [font="Times]}
0/f|ZH ~! [font="Times] do…while 语句
,(x`zpp _ [font="Times] class DoWhile {
}>BNdm"Er [font="Times]public static void main(String args[]) {
Bj\
x [font="Times]int n = 10;
Ka(B&. [font="Times]do {
'{
=F/q [font="Times]System.out.println("tick " + n);
P`Ku.
ONQ [font="Times]n--;
Fh)xm* u( [font="Times]} while(n > 0);
jH<Sf: Y( [font="Times]}
SEzjc ~@3 [font="Times]}
,ESli/6 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。
f]%SFQ+ [font="Times] for语句
ig.Z,R3@r [font="Times] class ForTick {
v;
#y^O
[font="Times]public static void main(String args[]) {
v\?J=|S+ [font="Times]int n;
|wuTw| [font="Times]for(n=10; n>0; n--)
A)n_ST0 [font="Times]System.out.println("tick " + n);
k0V]<#h87 [font="Times]}
nN<,rN{: [font="Times]}
IWq\M,P 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。
i&6U5Va,G 还有啊,[font="Times]for循环的部分可以为空的
vPYHM2 [font="Times]class ForVar {
%4!^AA% [font="Times]public static void main(String args[]) {
#*CMf.OCh [font="Times]int i;
7_s+7x = [font="Times]boolean done = false;
B(s^(__] [font="Times]i = 0;
8TB|Y [font="Times]for( ; !done; ) {
m"Mj3Z: [font="Times]System.out.println("i is " + i);
r4iNX+h?V [font="Times]if(i == 10) done = true;
V||b%Cb1g [font="Times]i++;
zx\-He [font="Times]}
de W1>yh^_ [font="Times]}
]FVJQS2h [font="Times]}
循环语句的例子下载 RA<ky*^dr [font="Times] 2.分支语句[font="Times]
WIi,`/K+ [font="Times] if/else语句
VZcW
3/Y [font="Times]class IfElse {
>fP;H}S6 [font="Times]public static void main(String args[]) {
+?"F=.SZ [font="Times]int month = 4; // April
I[K4/91 [font="Times]String season;
AH'c:w]~ [font="Times]if(month == 12 || month == 1 || month == 2)
!zOj`lx [font="Times]season = "Winter";
)HE{`yiLL [font="Times]else if(month == 3 || month == 4 || month == 5)
TX$dxHSPK [font="Times]season = "Spring";
u=qK_$d4 [font="Times]else if(month == 6 || month == 7 || month == 8)
)m
=xf1 [font="Times]season = "Summer";
y$-@|M$GG [font="Times]else if(month == 9 || month == 10 || month == 11)
?eX$Wc{ [font="Times]season = "Autumn";
AeEdqX) [font="Times]else
71[?AmxV [font="Times]season = "Bogus Month";
~3gazTe9 [font="Times]System.out.println("April is in the " + season + ".");
l@GJcCufE [font="Times]}
hE=xS:6 [font="Times]}
OV;VsF [font="Times]//这段程序输出[font="Times]:
iLBORT!; [font="Times]//April is in the Spring.
&)Qq%\EP4 [font="Times]// 注意[font="Times] “[font="Times]||”是或运算
#OM'2@ [font="Times] switch语句
MCibYvc[ [font="Times] class Switch {
P2jh[a% [font="Times]public static void main(String args[]) {
dcmf~+T [font="Times]int month = 4;
=6ru%.8U, [font="Times]String season;
1gBLJ0q [font="Times]switch (month) {
jcj8w [font="Times]case 12:
N}n3 +F [font="Times]case 1:
CQ6I4k [font="Times]case 2:
H0"'jd [font="Times]season = "Winter";
J'ce?_\?PY [font="Times]break;
(S W6?5 [font="Times]case 3:
+i!HMyM [font="Times]case 4:
Gu$J;bXVj [font="Times]case 5:
e6_8f*o|s [font="Times]season = "Spring";
pEcYfj3M [font="Times]break;
2C:u)}R7D [font="Times]case 6:
r{r~!=u [font="Times]case 7:
\`~YW<D [font="Times]case 8:
]3,9."^ [font="Times]season = "Summer";
{~9HJDcM [font="Times]break;
e{87n>+, [font="Times]case 9:
n;:.UGl9. [font="Times]case 10:
.+XK>jl+ [font="Times]case 11:
G.L}VpopM [font="Times]season = "Autumn";
deYv&=SPl [font="Times]break;
/# Jvt [font="Times]default:
1-^D2B[- [font="Times]season = "Bogus Month";
gd#R7[AVi [font="Times]}
+j F|8 [font="Times]System.out.println("April is in the " + season + ".");
G-1qxK [font="Times]}
?q4`&";{3 [font="Times]}
分支语句代码下载 ly34aD/p~, q
6UZ`9&z [font="Times]switch语句适合于条件非常多的逻辑
lbt8S.fx 请看上述语句可以混合使用,请看
下载例子