全新java初学者实践教程6(Java SE5.0版)
T[i7C3QS 基本语法3
^t\kLU jHs<s`#h )$ ofl%+ 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:
jf$JaY C_;HaQiu [font="Times] 1.循环语句[font="Times]:while,do-while,for
XD;15a #g@ [font="Times]2.分支语句[font="Times]:if-else,switch,
l84h%, [font="Times]
a/`c ef 3.跳转语句[font="Times] break,continue,label: 和[font="Times]return
"2)+)Db [font="Times]
>Sc$R0 4.异常处理语句[font="Times]:try-catch-finally,throw
wm); aWP D< nlb- 实践:
z1Bj_u{ [font="Times] 1.循环语句
:NwMb^> [font="Times] while 语句
P`\m9"7 [font="Times]class While {
NWo7wVwc/c [font="Times]public static void main(String args[]) {
Fy}MXe"f [font="Times]int n = 10;
vDu0 [font="Times]while(n > 0) {
^/`#9]<% [font="Times]System.out.println("tick " + n);
a<OCO0irJ [font="Times]n--;
=$"zqa.B6 [font="Times]}
5?V? [font="Times]}
Bg+<*z-?e [font="Times]}
"/4s8.dw+u [font="Times] do…while 语句
O ,Pl7x%tK [font="Times] class DoWhile {
,omp F$% [font="Times]public static void main(String args[]) {
<.PPs:{8# [font="Times]int n = 10;
L Q I: ]d [font="Times]do {
s,UN'~e1 [font="Times]System.out.println("tick " + n);
jjS{q,bo [font="Times]n--;
^}i50SG:y [font="Times]} while(n > 0);
W (=Wg|cr [font="Times]}
;kyL>mV{ [font="Times]}
XEf&Yd 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。
'k-u9 [font="Times] for语句
:$SRG^7md [font="Times] class ForTick {
nLFx/5sL [font="Times]public static void main(String args[]) {
?)Czl4J [font="Times]int n;
L}e"nzTE6I [font="Times]for(n=10; n>0; n--)
`}k&HRn [font="Times]System.out.println("tick " + n);
1jUhG2y [font="Times]}
E< zT [font="Times]}
~uhyROO,G" 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。
!LHzY( 还有啊,[font="Times]for循环的部分可以为空的
#lBpln9 [font="Times]class ForVar {
C>w9
{h [font="Times]public static void main(String args[]) {
`mq4WXO\ [font="Times]int i;
X%4uShM [font="Times]boolean done = false;
e6{[o@aM{ [font="Times]i = 0;
c:h.J4mv [font="Times]for( ; !done; ) {
h9Tf@]W
[font="Times]System.out.println("i is " + i);
gCk y(4 [font="Times]if(i == 10) done = true;
jM3Y|}+ [font="Times]i++;
F$6])F [font="Times]}
#FQm/Q<0 [font="Times]}
!\&7oAs=I [font="Times]}
循环语句的例子下载 j$|Yd= [font="Times] 2.分支语句[font="Times]
<iXS0k [font="Times] if/else语句
4P O%qO [font="Times]class IfElse {
-~<q,p"e [font="Times]public static void main(String args[]) {
X5L(_0?F1 [font="Times]int month = 4; // April
T}w*K[z
$ [font="Times]String season;
2vh!pez_ [font="Times]if(month == 12 || month == 1 || month == 2)
zgq_0w~X [font="Times]season = "Winter";
zCGmn& *M [font="Times]else if(month == 3 || month == 4 || month == 5)
c5=v`hv [font="Times]season = "Spring";
h87L8qh9 [font="Times]else if(month == 6 || month == 7 || month == 8)
#5ohmp,u [font="Times]season = "Summer";
mf*9^}l+Zn [font="Times]else if(month == 9 || month == 10 || month == 11)
ld!6|~0U [font="Times]season = "Autumn";
Eis%)oE
[font="Times]else
/8$1[[[ [font="Times]season = "Bogus Month";
\[IdR^<YM [font="Times]System.out.println("April is in the " + season + ".");
m m J)m [font="Times]}
?G>5 D`V [font="Times]}
PO%yWns30o [font="Times]//这段程序输出[font="Times]:
4ye`;hXy [font="Times]//April is in the Spring.
CQ8o9A/ [font="Times]// 注意[font="Times] “[font="Times]||”是或运算
(1elF) [font="Times] switch语句
w}bEufU+2 [font="Times] class Switch {
N}l]Ilm$34 [font="Times]public static void main(String args[]) {
/K1$_ [font="Times]int month = 4;
SRG!G]?- [font="Times]String season;
:d%
-,v [font="Times]switch (month) {
Iu1Sj`A [font="Times]case 12:
RZV1:hNN [font="Times]case 1:
2LxVt@_R!% [font="Times]case 2:
#a'x)$2;R| [font="Times]season = "Winter";
vY0V{u?J [font="Times]break;
~U7\ LBF [font="Times]case 3:
QzFv ; [font="Times]case 4:
uu@'02G8 [font="Times]case 5:
m|ERf 2- [font="Times]season = "Spring";
!(ux.T0 [font="Times]break;
rt@-Pw!B [font="Times]case 6:
SbPjU50 [font="Times]case 7:
dnX`F5zd [font="Times]case 8:
Z;~E+dXC [font="Times]season = "Summer";
0m+5Zn [font="Times]break;
[^(R1K [font="Times]case 9:
"PX3%II [font="Times]case 10:
TNFm7}= [font="Times]case 11:
EkjK92cF [font="Times]season = "Autumn";
rCSG@D. [font="Times]break;
2`FsG/o\T~ [font="Times]default:
?;KJ
(@Va [font="Times]season = "Bogus Month";
j=jrzG+` [font="Times]}
{u_k\m[Y [font="Times]System.out.println("April is in the " + season + ".");
KEVy%AP=*h [font="Times]}
]g-qWSKU [font="Times]}
分支语句代码下载 -< dMD_ n"d) [font="Times]switch语句适合于条件非常多的逻辑
|v%RjN 请看上述语句可以混合使用,请看
下载例子