全新java初学者实践教程6(Java SE5.0版)
rjK]zD9 基本语法3
PI\C*_. 'VgEf:BS "?%2`*\ 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:
TB}6iIe 'uC=xG.*} [font="Times] 1.循环语句[font="Times]:while,do-while,for
W{m_yEOf mF:Pplf< [font="Times]2.分支语句[font="Times]:if-else,switch,
5o6X.sC8e [font="Times]
%u}#|+8} 3.跳转语句[font="Times] break,continue,label: 和[font="Times]return
-*A1[Z ? [font="Times]
-w"$[XP 4.异常处理语句[font="Times]:try-catch-finally,throw
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,\*)5 ]sTb Ew.[ 实践:
s<>d&W 0= [font="Times] 1.循环语句
sZx`u+ [font="Times] while 语句
2cEvsvw> [font="Times]class While {
{8I,uQO [font="Times]public static void main(String args[]) {
S=}1k,I [font="Times]int n = 10;
brCXimG&jo [font="Times]while(n > 0) {
'Zs3b4n8 [font="Times]System.out.println("tick " + n);
{oSdVRI [font="Times]n--;
6l'J!4*qY [font="Times]}
U ,NGV0 [font="Times]}
YdDP;,
DA [font="Times]}
fUMjLA|*I< [font="Times] do…while 语句
iGPrWe@. [font="Times] class DoWhile {
OxQ 5P;O [font="Times]public static void main(String args[]) {
&V|kv"Wwj [font="Times]int n = 10;
w_h{6Kc< [font="Times]do {
cgnMoBIc [font="Times]System.out.println("tick " + n);
LLc^SP j [font="Times]n--;
Q5c3C&$6 [font="Times]} while(n > 0);
/!?b&N/d) [font="Times]}
EHy 15RL [font="Times]}
> ^=n|% 二者区别,[font="Times]do…while至少循环一次,而[font="Times]while的表达式要是为[font="Times]flase的话可以一次也不循环。再通俗一点,[font="Times]do…while就算是括号里的是[font="Times]flase,人家最少也能[font="Times]do一次。
~R&rQJJeJ [font="Times] for语句
qj9[mBkP" [font="Times] class ForTick {
U&i#cF [font="Times]public static void main(String args[]) {
Z`_x|cU?J [font="Times]int n;
Y'{}L@"t [font="Times]for(n=10; n>0; n--)
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[font="Times]System.out.println("tick " + n);
!2kM [font="Times]}
Na$.VT [font="Times]}
in K]+H]{ 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。
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AK 还有啊,[font="Times]for循环的部分可以为空的
Pbd[gKX_ [font="Times]class ForVar {
_@i-?Q [font="Times]public static void main(String args[]) {
*I!R0;HT [font="Times]int i;
}uNj#Uf [font="Times]boolean done = false;
mqHcD8X [font="Times]i = 0;
wPEK5=\4Ob [font="Times]for( ; !done; ) {
xax[#Vl4 [font="Times]System.out.println("i is " + i);
c2t`i [font="Times]if(i == 10) done = true;
R#3zGWr~ [font="Times]i++;
6cd!;Ca [font="Times]}
A!,c@Kv
3 [font="Times]}
zMRa<G7 [font="Times]}
循环语句的例子下载 N5{v;~Cm}V [font="Times] 2.分支语句[font="Times]
tm/=Oc1p [font="Times] if/else语句
Tdade+ [font="Times]class IfElse {
t>Ye*eR*`U [font="Times]public static void main(String args[]) {
?N<,;~ [font="Times]int month = 4; // April
4[i 3ckFT, [font="Times]String season;
~j>yQ%[v [font="Times]if(month == 12 || month == 1 || month == 2)
9N `WT= [font="Times]season = "Winter";
X!:J1'FE [font="Times]else if(month == 3 || month == 4 || month == 5)
V:#rY5X [font="Times]season = "Spring";
gg.]\#3g [font="Times]else if(month == 6 || month == 7 || month == 8)
oP`:NCj\9 [font="Times]season = "Summer";
<THwl/a [font="Times]else if(month == 9 || month == 10 || month == 11)
6fo\z2 [font="Times]season = "Autumn";
@ R[K8 [font="Times]else
`*cqT [font="Times]season = "Bogus Month";
j85B{Mab& [font="Times]System.out.println("April is in the " + season + ".");
m62Zta [font="Times]}
w[F})u]E [font="Times]}
8nng^ [font="Times]//这段程序输出[font="Times]:
=/}Rnl+c [font="Times]//April is in the Spring.
e]nP7TIU [font="Times]// 注意[font="Times] “[font="Times]||”是或运算
oKYa? [font="Times] switch语句
'Kk/
J+6U [font="Times] class Switch {
>;XtJJS [font="Times]public static void main(String args[]) {
[
:)F- [font="Times]int month = 4;
"f8,9@ [font="Times]String season;
hP8w3gl_ [font="Times]switch (month) {
0r_~LN^|[ [font="Times]case 12:
Oe
x
[font="Times]case 1:
]h~F%
[font="Times]case 2:
i9Beap/t$ [font="Times]season = "Winter";
0J^Z)U>j [font="Times]break;
H#7=s{u [font="Times]case 3:
*Lxt{z`9 [font="Times]case 4:
c0Bqm [font="Times]case 5:
wm^1Fn-- [font="Times]season = "Spring";
}-sh [font="Times]break;
w,X)g{^T [font="Times]case 6:
SHs [te[ [font="Times]case 7:
Lc?"4 [font="Times]case 8:
g%tUk M [font="Times]season = "Summer";
z:Tj0<A' [font="Times]break;
n-2!<`UFX [font="Times]case 9:
tH&eKM4G [font="Times]case 10:
[<5/s$,i [font="Times]case 11:
yZ 7)|j [font="Times]season = "Autumn";
Vpp$yM&? [font="Times]break;
dH.Fb/7f [font="Times]default:
G62;p# [font="Times]season = "Bogus Month";
>?OUs>}3y2 [font="Times]}
T u%XhXl:j [font="Times]System.out.println("April is in the " + season + ".");
l?$X.CwX [font="Times]}
>]anTF`d [font="Times]}
分支语句代码下载 M*bsA/Z Y[vP]7- [font="Times]switch语句适合于条件非常多的逻辑
2+I5VPf 请看上述语句可以混合使用,请看
下载例子