全新java初学者实践教程6(Java SE5.0版)
Tv6HPD$[ 基本语法3
nXT/zfS fWz=bJ"V WXs?2S* 我们这个教程侧重的是实践的内容和语言的重点。在[font="Times]java语言中还有很多细节的东西,请参考[font="Times]sun公司的官方培训教程。我们这里不能一一讲述。这节课我们来给大家提供一些程序流程控制的一些例子供大家学习。计算机怎么做事情,是我们教给他的。我们用它解决实际生活中的问题,所以计算机要描述现实生活中的流程。[font="Times]Java语言中提供了[font="Times]4类程序控制语句,来描述流程:
'D:R]@eK] h3rVa6cxM [font="Times] 1.循环语句[font="Times]:while,do-while,for
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4Gt^:J" [font="Times]2.分支语句[font="Times]:if-else,switch,
wM1&_%N [font="Times]
1'YUK"i 3.跳转语句[font="Times] break,continue,label: 和[font="Times]return
H#/Hs# [font="Times]
`V2doV) 4.异常处理语句[font="Times]:try-catch-finally,throw
ufn%sA &[7z:`+Y## 实践:
E"zC6iYZ; [font="Times] 1.循环语句
'>k1h.i [font="Times] while 语句
g-4j1yJV< [font="Times]class While {
| r,{# EE [font="Times]public static void main(String args[]) {
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"G* [font="Times]int n = 10;
jRN>^Ur;g [font="Times]while(n > 0) {
W+I""I*mV [font="Times]System.out.println("tick " + n);
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[font="Times]n--;
U8a5rF>< [font="Times]}
c+upoM [font="Times]}
8bdx$,$k [font="Times]}
&Lbh?C [font="Times] do…while 语句
hplx s# [font="Times] class DoWhile {
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H [font="Times]public static void main(String args[]) {
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[font="Times]int n = 10;
~5o2jTNy`p [font="Times]do {
-
VdCj%r> [font="Times]System.out.println("tick " + n);
3vHkhhYQ [font="Times]n--;
{8"Uxj_6V [font="Times]} while(n > 0);
|pZ:5ta# [font="Times]}
c"diNbm[ [font="Times]}
B:VGa<lx5 二者区别,[font="Times]do…while至少循环一次,而[font="Times]while的表达式要是为[font="Times]flase的话可以一次也不循环。再通俗一点,[font="Times]do…while就算是括号里的是[font="Times]flase,人家最少也能[font="Times]do一次。
X#o<)) [font="Times] for语句
/5X_gjOL, [font="Times] class ForTick {
AO,^v+$ [font="Times]public static void main(String args[]) {
#sE:xIR [font="Times]int n;
k'NP+N<M [font="Times]for(n=10; n>0; n--)
`LNKbTc[m [font="Times]System.out.println("tick " + n);
D67z6jep( [font="Times]}
x~ID[ [font="Times]}
\olY)b[ 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。
n?QglN 还有啊,[font="Times]for循环的部分可以为空的
d~q7! [font="Times]class ForVar {
X!6$<8+1OV [font="Times]public static void main(String args[]) {
)"J1ET,z [font="Times]int i;
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] [font="Times]boolean done = false;
n}C0gt- [font="Times]i = 0;
Wf~PP; [font="Times]for( ; !done; ) {
OBf$Z"i [font="Times]System.out.println("i is " + i);
`neo.] [font="Times]if(i == 10) done = true;
^iWJqpLe [font="Times]i++;
5cb8=W- [font="Times]}
nG$+9}\UlP [font="Times]}
<Ira~N [font="Times]}
循环语句的例子下载 [Wxf,rW i [font="Times] 2.分支语句[font="Times]
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@ [font="Times] if/else语句
,u9>c*Ss\ [font="Times]class IfElse {
1~E;@eK' [font="Times]public static void main(String args[]) {
\odns [font="Times]int month = 4; // April
Oc-ia)v1G [font="Times]String season;
N36B*9m&p [font="Times]if(month == 12 || month == 1 || month == 2)
ce*?crOV [font="Times]season = "Winter";
+:W? :\ [font="Times]else if(month == 3 || month == 4 || month == 5)
.HRd6O; [font="Times]season = "Spring";
Htfq?\ FD [font="Times]else if(month == 6 || month == 7 || month == 8)
5=Y(.}6 [font="Times]season = "Summer";
1tTY)Evf [font="Times]else if(month == 9 || month == 10 || month == 11)
I:0dz:T7* [font="Times]season = "Autumn";
],vid1E [font="Times]else
7%G&=8tq [font="Times]season = "Bogus Month";
c=^69>w [font="Times]System.out.println("April is in the " + season + ".");
7PwH&rI [font="Times]}
;9q$eK%d [font="Times]}
1~j,A[&|< [font="Times]//这段程序输出[font="Times]:
m>?|*a, [font="Times]//April is in the Spring.
,XI=e= [font="Times]// 注意[font="Times] “[font="Times]||”是或运算
m)]|mYjju [font="Times] switch语句
4G hg~0 [font="Times] class Switch {
qQ1D }c@ [font="Times]public static void main(String args[]) {
?j)#\s2 [font="Times]int month = 4;
{Z1-B60P [font="Times]String season;
t3C#$> [font="Times]switch (month) {
bJkFCI/ [font="Times]case 12:
]7RK/Zu i [font="Times]case 1:
Zu>CR_C [font="Times]case 2:
v[R_6 [font="Times]season = "Winter";
5HTY ~&C [font="Times]break;
lwo,D} [font="Times]case 3:
B B^81{A [font="Times]case 4:
SRU#Y8Xv| [font="Times]case 5:
>SS^qjh/ [font="Times]season = "Spring";
A0Q1"b= [font="Times]break;
/Ao.b|mm [font="Times]case 6:
Mko,((>I1 [font="Times]case 7:
" LhXR [font="Times]case 8:
|/Y!R>El [font="Times]season = "Summer";
}:1qK67S [font="Times]break;
I*mBU^<9V [font="Times]case 9:
=/4}!B/ [font="Times]case 10:
84s:cO [font="Times]case 11:
2P{! n#" [font="Times]season = "Autumn";
\lyHQ-gWhc [font="Times]break;
BZjL\{IW [font="Times]default:
W9bpKmc [font="Times]season = "Bogus Month";
6)FM83zk)K [font="Times]}
w;J#+ik [font="Times]System.out.println("April is in the " + season + ".");
yA`,ns&n [font="Times]}
:K(+ KN( [font="Times]}
分支语句代码下载 RER93:( k9c`[M [font="Times]switch语句适合于条件非常多的逻辑
Z'm( M[2K 请看上述语句可以混合使用,请看
下载例子