全新java初学者实践教程6(Java SE5.0版)
O PJ(ub 基本语法3
oq[r+E-]$@ L3Ivm: vY);7 我们这个教程侧重的是实践的内容和语言的重点。在[font="Times]java语言中还有很多细节的东西,请参考[font="Times]sun公司的官方培训教程。我们这里不能一一讲述。这节课我们来给大家提供一些程序流程控制的一些例子供大家学习。计算机怎么做事情,是我们教给他的。我们用它解决实际生活中的问题,所以计算机要描述现实生活中的流程。[font="Times]Java语言中提供了[font="Times]4类程序控制语句,来描述流程:
pMV ?vH *X8Pa;x [font="Times] 1.循环语句[font="Times]:while,do-while,for
c]A @'{7 zvR;Tl6] [font="Times]2.分支语句[font="Times]:if-else,switch,
iiv`ji [font="Times]
C@!bd+' 3.跳转语句[font="Times] break,continue,label: 和[font="Times]return
m*vz [font="Times]
V<Co!2S 4.异常处理语句[font="Times]:try-catch-finally,throw
hQwUwfoe@ 21z@-&Oq 实践:
<{IeCir [font="Times] 1.循环语句
TFDzTD [font="Times] while 语句
?\_vqW [font="Times]class While {
lY[\eQ
1: [font="Times]public static void main(String args[]) {
zuI7Px [font="Times]int n = 10;
3 EOuJ [font="Times]while(n > 0) {
FZtT2Z4&i [font="Times]System.out.println("tick " + n);
L b-xc] [font="Times]n--;
wo9`-o6 [font="Times]}
S~U5xM^s [font="Times]}
A@jBn6 [font="Times]}
#@m6ag. [font="Times] do…while 语句
J+l#!gk$! [font="Times] class DoWhile {
&Xh=bM'/%m [font="Times]public static void main(String args[]) {
lw_@(E]E [font="Times]int n = 10;
aj]pN,g@N [font="Times]do {
KN'twPFq [font="Times]System.out.println("tick " + n);
\0.!al0 [font="Times]n--;
K6s tkDhb [font="Times]} while(n > 0);
h>ZU67- [font="Times]}
=\)76xC20 [font="Times]}
\?[ m%$A 二者区别,[font="Times]do…while至少循环一次,而[font="Times]while的表达式要是为[font="Times]flase的话可以一次也不循环。再通俗一点,[font="Times]do…while就算是括号里的是[font="Times]flase,人家最少也能[font="Times]do一次。
i4lB]k [font="Times] for语句
>OKc\m2%Q [font="Times] class ForTick {
<.:mp1,8V [font="Times]public static void main(String args[]) {
t(1gJZs>kX [font="Times]int n;
T'a& [font="Times]for(n=10; n>0; n--)
x\ 8gb#8 [font="Times]System.out.println("tick " + n);
zQoJ8i> [font="Times]}
R~BFZF>: [font="Times]}
\ESNfL5 与上面那两个的区别,[font="Times]for循环执行的次数是可以在执行之前确定的。通俗一点说吧,看这个例子[font="Times] for(n=10; n>0; n--)就是在括号里的时候,就已经知道要循环[font="Times]10次了。
5MK.>3fE 还有啊,[font="Times]for循环的部分可以为空的
)}@Z*.HZL [font="Times]class ForVar {
+>Pq]{Uf1j [font="Times]public static void main(String args[]) {
j-zWckT{ [font="Times]int i;
'j;i4ie>*x [font="Times]boolean done = false;
?dmwz4k0 [font="Times]i = 0;
n^` `)" [font="Times]for( ; !done; ) {
#r QT)n [font="Times]System.out.println("i is " + i);
\jr-^n] [font="Times]if(i == 10) done = true;
T;v^BVn [font="Times]i++;
Se|h]+G [font="Times]}
|8fdhqy_ [font="Times]}
FpZ5@ [font="Times]}
循环语句的例子下载 +de5y]1H,| [font="Times] 2.分支语句[font="Times]
4iY
<7l8 [font="Times] if/else语句
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!Rzl< [font="Times]class IfElse {
lL&p?MUp [font="Times]public static void main(String args[]) {
<7o@7r'0 [font="Times]int month = 4; // April
WS"v"J% [font="Times]String season;
,{d=<j_ [font="Times]if(month == 12 || month == 1 || month == 2)
\6!s";=hQ [font="Times]season = "Winter";
Ict+|<f [font="Times]else if(month == 3 || month == 4 || month == 5)
J9P\D! [font="Times]season = "Spring";
GQ}R xu] [font="Times]else if(month == 6 || month == 7 || month == 8)
j]m|}n [font="Times]season = "Summer";
3v3`d+;& [font="Times]else if(month == 9 || month == 10 || month == 11)
w:2yFC [font="Times]season = "Autumn";
]W7&ZpF [font="Times]else
Si68_]:^ [font="Times]season = "Bogus Month";
n/^QPR$>. [font="Times]System.out.println("April is in the " + season + ".");
(I;lE*> [font="Times]}
A_+*b
[P [font="Times]}
R)Dh; XA [font="Times]//这段程序输出[font="Times]:
[ZD`t,x( [font="Times]//April is in the Spring.
X/H2c"!t [font="Times]// 注意[font="Times] “[font="Times]||”是或运算
)2J#pz?. [font="Times] switch语句
EUS^Gtc [font="Times] class Switch {
1-Q>[Uz, [font="Times]public static void main(String args[]) {
ceAefKdb [font="Times]int month = 4;
Ryn@">sVI [font="Times]String season;
u?KG% [font="Times]switch (month) {
M1I4Ot [font="Times]case 12:
tDtqTB} [font="Times]case 1:
Qm4cuV-0{ [font="Times]case 2:
^+Njz{rpG [font="Times]season = "Winter";
z5W;-sCz [font="Times]break;
J7k=5Fqej; [font="Times]case 3:
5"w% [font="Times]case 4:
Tx(=4ALY [font="Times]case 5:
7eG@)5Uy [font="Times]season = "Spring";
c+jnQM' [font="Times]break;
i}>}%l| [font="Times]case 6:
Oyp)Wm;@ [font="Times]case 7:
._<gc;G [font="Times]case 8:
9mEhZ" [font="Times]season = "Summer";
%3T:W\h [font="Times]break;
GuQ# [font="Times]case 9:
e r"gPW [font="Times]case 10:
`3.bux~ [font="Times]case 11:
a]4|XJ_ [font="Times]season = "Autumn";
8},fu3Z [font="Times]break;
JB HnJm [font="Times]default:
r6L [font="Times]season = "Bogus Month";
!%QbE[Kl> [font="Times]}
Tx/KL%X [font="Times]System.out.println("April is in the " + season + ".");
!={QL : [font="Times]}
I bE Nq [font="Times]}
分支语句代码下载 w^/"j_p@ ;h#CT#R2 [font="Times]switch语句适合于条件非常多的逻辑
M \>5" ,0 请看上述语句可以混合使用,请看
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