全新java初学者实践教程6(Java SE5.0版)
<h:x= 基本语法3
kY-N>E: Z/Dx,zIR W*),y: 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:
woGAf)vV# 0"28' [font="Times] 1.循环语句[font="Times]:while,do-while,for
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a!$z!. x"~8*V'0 [font="Times]2.分支语句[font="Times]:if-else,switch,
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o <pf#tifv 3.跳转语句[font="Times] break,continue,label: 和[font="Times]return
+ |n*b [font="Times]
JR@`2YP- 4.异常处理语句[font="Times]:try-catch-finally,throw
hG12ZZ D EVsC >rz 实践:
f'EuY17w [font="Times] 1.循环语句
0dE@c./R i [font="Times] while 语句
VJ]JjB
j [font="Times]class While {
CVL3VT1j0 [font="Times]public static void main(String args[]) {
42$VhdG [font="Times]int n = 10;
-"'j7t: [font="Times]while(n > 0) {
F%@aB<Nu [font="Times]System.out.println("tick " + n);
BBwy,\o# [font="Times]n--;
128EPK [font="Times]}
i:Y^{\Z?V [font="Times]}
+M\`#i\g> [font="Times]}
q_A!'sm@) [font="Times] do…while 语句
Vt:~q{9*k [font="Times] class DoWhile {
iTgt}]L [font="Times]public static void main(String args[]) {
OR~8sU [font="Times]int n = 10;
<lx+/o [font="Times]do {
&8Cu#^3
[font="Times]System.out.println("tick " + n);
mwHB(7YS, [font="Times]n--;
$P^q!H4D [font="Times]} while(n > 0);
S2sQOM@ [font="Times]}
N4F.Y"R$( [font="Times]}
6xTuNE1 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。
:LF? [font="Times] for语句
5\:^y'g[ [font="Times] class ForTick {
-*X a3/kQ [font="Times]public static void main(String args[]) {
*x@Onj [font="Times]int n;
.WA-&b_ [font="Times]for(n=10; n>0; n--)
CQF:Rnb [font="Times]System.out.println("tick " + n);
RzE_K'M [font="Times]}
Lo{
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S"NqM[W 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。
2_HNhW
还有啊,[font="Times]for循环的部分可以为空的
J\twZ>w~0 [font="Times]class ForVar {
6-N?mSQU [font="Times]public static void main(String args[]) {
N} G[7Rp8l [font="Times]int i;
%*A0# F [font="Times]boolean done = false;
.sha& [font="Times]i = 0;
#rMlI3; [font="Times]for( ; !done; ) {
.o(fe\KHf [font="Times]System.out.println("i is " + i);
U)fc*s [font="Times]if(i == 10) done = true;
Rr&h!YMb [font="Times]i++;
JjtNP)We [font="Times]}
yVU^M?`# [font="Times]}
:}'=`wa [font="Times]}
循环语句的例子下载 e^6)Zz1\ [font="Times] 2.分支语句[font="Times]
<wN}X#M [font="Times] if/else语句
Y,<{vLEC [font="Times]class IfElse {
:~"CuB/ [font="Times]public static void main(String args[]) {
:~&~y-14 [font="Times]int month = 4; // April
FH?U(- [font="Times]String season;
\)#kquH/l [font="Times]if(month == 12 || month == 1 || month == 2)
1H?
u Qy [font="Times]season = "Winter";
I| w"/"U [font="Times]else if(month == 3 || month == 4 || month == 5)
x
nsLf?>] [font="Times]season = "Spring";
AifWf2$S [font="Times]else if(month == 6 || month == 7 || month == 8)
<'y?KiphL [font="Times]season = "Summer";
cOmw?kA*G [font="Times]else if(month == 9 || month == 10 || month == 11)
n9W(bG o [font="Times]season = "Autumn";
'N (:@]4N [font="Times]else
(-UYB9s [font="Times]season = "Bogus Month";
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c] [font="Times]System.out.println("April is in the " + season + ".");
KKja/p [font="Times]}
aL+
o / [font="Times]}
T0wW<_jh [font="Times]//这段程序输出[font="Times]:
=upeRY@u5 [font="Times]//April is in the Spring.
u^@f&BIG]: [font="Times]// 注意[font="Times] “[font="Times]||”是或运算
}eCw6 [font="Times] switch语句
H%qsjB^ [font="Times] class Switch {
1gL2ia [font="Times]public static void main(String args[]) {
b|l:fT?& [font="Times]int month = 4;
#^u$ [font="Times]String season;
eBZXI)pPh [font="Times]switch (month) {
.F98G/s [font="Times]case 12:
TV)h`\|Z* [font="Times]case 1:
M'7f O3&| [font="Times]case 2:
M8MRoA6F [font="Times]season = "Winter";
2V-
16Q'% [font="Times]break;
v|XTr,# [font="Times]case 3:
| k&Ck [font="Times]case 4:
CpUkCgg [font="Times]case 5:
?AK(| [font="Times]season = "Spring";
<GS^ [font="Times]break;
Xb|:vr\v [font="Times]case 6:
dU&a{$ku[ [font="Times]case 7:
{2O1"|s , [font="Times]case 8:
Ci@o|Y }tP [font="Times]season = "Summer";
f%is~e~wc [font="Times]break;
pNG:0 [font="Times]case 9:
C)[,4wt, [font="Times]case 10:
x,=&JtKVc [font="Times]case 11:
{%rA1g [font="Times]season = "Autumn";
zJq~!#pZ [font="Times]break;
:}He\V [font="Times]default:
D$w6V [font="Times]season = "Bogus Month";
b o6d)Q [font="Times]}
LdYB7T,
[font="Times]System.out.println("April is in the " + season + ".");
H[6:_**?o [font="Times]}
^h(ew1: [font="Times]}
分支语句代码下载 x>**;#7) }~YA5^VQ$ [font="Times]switch语句适合于条件非常多的逻辑
KoOz#,() 请看上述语句可以混合使用,请看
下载例子