全新java初学者实践教程6(Java SE5.0版)
a[iuE` 基本语法3
4 f/2gI1@B zJNiAc V,?i]q;5 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:
{Lu-!}\NP >$h *1/ [font="Times] 1.循环语句[font="Times]:while,do-while,for
co<-gy/mCR x j~/C5@ [font="Times]2.分支语句[font="Times]:if-else,switch,
GEU:xn [font="Times]
.-t#wXEi 3.跳转语句[font="Times] break,continue,label: 和[font="Times]return
ehQ"<.sQ [font="Times]
i_?";5B" 4.异常处理语句[font="Times]:try-catch-finally,throw
y\&GPr fNOsB^Y 实践:
K:&FWl. [font="Times] 1.循环语句
.ky(( [font="Times] while 语句
z+5l:f [font="Times]class While {
rjfcZ@ [font="Times]public static void main(String args[]) {
=pQA!u]QE [font="Times]int n = 10;
*x3";%o [font="Times]while(n > 0) {
CYA#: [font="Times]System.out.println("tick " + n);
4G;FpWQm [font="Times]n--;
[|PVq#( [font="Times]}
7:x%^J+ [font="Times]}
B,?Fjot#m [font="Times]}
uKF?UXc [font="Times] do…while 语句
sr%tEKba) [font="Times] class DoWhile {
=)}m4,LA [font="Times]public static void main(String args[]) {
+-~hl [font="Times]int n = 10;
5^lroC-(x [font="Times]do {
j&n][=PL [font="Times]System.out.println("tick " + n);
hXr`S4aJ [font="Times]n--;
!l!^`c [font="Times]} while(n > 0);
(.TkvUj` [font="Times]}
-#srn1A> [font="Times]}
tX)l$oRPr 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。
tpw0j
CVu [font="Times] for语句
iR
j/Tm*T' [font="Times] class ForTick {
a86m?)-c [font="Times]public static void main(String args[]) {
FtbqZN[ [font="Times]int n;
csZIBi [font="Times]for(n=10; n>0; n--)
j.O7-t%C [font="Times]System.out.println("tick " + n);
T;D`=p# [font="Times]}
5m2(7FC%su [font="Times]}
WK5~"aw 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。
6kH47Yc? 还有啊,[font="Times]for循环的部分可以为空的
1{\{'EP{ [font="Times]class ForVar {
V*P3C5l [font="Times]public static void main(String args[]) {
7e$\|~< [font="Times]int i;
(3YqM7cqt [font="Times]boolean done = false;
F#S^Q` [font="Times]i = 0;
qGG [font="Times]for( ; !done; ) {
J{8_4s!Xt> [font="Times]System.out.println("i is " + i);
0&$+ CWSM [font="Times]if(i == 10) done = true;
JJJlgr]#
[font="Times]i++;
q
H&7Q{ [font="Times]}
}}Ah-QU [font="Times]}
seWYY $$ [font="Times]}
循环语句的例子下载 c`~aiC`l [font="Times] 2.分支语句[font="Times]
x]umh{H~ [font="Times] if/else语句
O8+e: K[D [font="Times]class IfElse {
>o #^r; [font="Times]public static void main(String args[]) {
'@'~_BBZP [font="Times]int month = 4; // April
\z!*)v/{- [font="Times]String season;
is&A_C7yg [font="Times]if(month == 12 || month == 1 || month == 2)
s6<`#KFAg [font="Times]season = "Winter";
UEmNT9V [font="Times]else if(month == 3 || month == 4 || month == 5)
S^|Uzc [font="Times]season = "Spring";
Y~]E6'Bz [font="Times]else if(month == 6 || month == 7 || month == 8)
3f9J!B`n [font="Times]season = "Summer";
}Y\Ayl [font="Times]else if(month == 9 || month == 10 || month == 11)
a x1 [font="Times]season = "Autumn";
)2T?Z)"hO [font="Times]else
^luAX
}* [font="Times]season = "Bogus Month";
(9q61zA [font="Times]System.out.println("April is in the " + season + ".");
"orZje9AC [font="Times]}
q)R&npP7 [font="Times]}
`[\*1GpAo [font="Times]//这段程序输出[font="Times]:
NyU~8?bp [font="Times]//April is in the Spring.
hPtSY'_@_ [font="Times]// 注意[font="Times] “[font="Times]||”是或运算
xXQ#?::m [font="Times] switch语句
Q:?]:i/* [font="Times] class Switch {
\M^L'Mkj [font="Times]public static void main(String args[]) {
Omo1p(y [font="Times]int month = 4;
i-!Z/,oL [font="Times]String season;
sxM0c [font="Times]switch (month) {
:Bc)1^I [font="Times]case 12:
U085qKyCw [font="Times]case 1:
De`)`\U [font="Times]case 2:
'9cShe [font="Times]season = "Winter";
\IY)2C<e [font="Times]break;
VyK]:n<5Q [font="Times]case 3:
5sui*WH [font="Times]case 4:
7m0sF<P{g [font="Times]case 5:
YGrmco?G [font="Times]season = "Spring";
I12WOL q [font="Times]break;
P6w!r>?6N [font="Times]case 6:
wic"a
Y<m [font="Times]case 7:
c"R`7P [font="Times]case 8:
eaP,MkK& [font="Times]season = "Summer";
N}x\Ll [font="Times]break;
}8cL+JJU [font="Times]case 9:
m@o/ W [font="Times]case 10:
<;\T
e4g[ [font="Times]case 11:
xvP<~N- [font="Times]season = "Autumn";
yiyyw,iy [font="Times]break;
WP&P#ju& [font="Times]default:
INrl^P* [font="Times]season = "Bogus Month";
t(/b'Peq [font="Times]}
|T7 < ! [font="Times]System.out.println("April is in the " + season + ".");
?2hoY [font="Times]}
Nzj7e 1= [font="Times]}
分支语句代码下载 [Lh<k+ @dE|UZ=( [font="Times]switch语句适合于条件非常多的逻辑
cA%70Y:AV 请看上述语句可以混合使用,请看
下载例子