全新java初学者实践教程6(Java SE5.0版)
~,T+JX 基本语法3
*y{+W "tKNlHBu' Gp,'kw"I 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:
x =h0Fq,T yu=piP [font="Times] 1.循环语句[font="Times]:while,do-while,for
# J]~ ;t|,nz4kJ [font="Times]2.分支语句[font="Times]:if-else,switch,
%w$mSG [font="Times]
?;_H{/)m 3.跳转语句[font="Times] break,continue,label: 和[font="Times]return
<z',]hy [font="Times]
+ZX.1[O 4.异常处理语句[font="Times]:try-catch-finally,throw
Y3<b~!f +|9f%f6vp 实践:
6i| ~7md, [font="Times] 1.循环语句
&;s<dDQK [font="Times] while 语句
V;k#})_- [font="Times]class While {
T RDxT [font="Times]public static void main(String args[]) {
3 tF: [font="Times]int n = 10;
vnL?O8`c [font="Times]while(n > 0) {
L$SMfx [font="Times]System.out.println("tick " + n);
T!(sZf [font="Times]n--;
TywK\hH [font="Times]}
.D!WO [font="Times]}
w]}f6VlEl [font="Times]}
^(DL+r, [font="Times] do…while 语句
J
B(<.E2 [font="Times] class DoWhile {
5~Q Tg [font="Times]public static void main(String args[]) {
1 )'Iu`k/ [font="Times]int n = 10;
[EER4@_ [font="Times]do {
<W2ZoqaV [font="Times]System.out.println("tick " + n);
xdqK.Z% [font="Times]n--;
7C?E z%a@ [font="Times]} while(n > 0);
Tv1]v. [font="Times]}
BtzYA" [font="Times]}
F*,5\s< 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。
mVt3WZa [font="Times] for语句
ncj!KyU [font="Times] class ForTick {
#hy+ L [font="Times]public static void main(String args[]) {
AC'lS
>7s [font="Times]int n;
>P<'L4; [font="Times]for(n=10; n>0; n--)
zC#%6@P\ [font="Times]System.out.println("tick " + n);
qEZ!2R^`G [font="Times]}
1LX)4TCC [font="Times]}
~XKZXGw 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。
R B%:h-t4 还有啊,[font="Times]for循环的部分可以为空的
4dD2{M [font="Times]class ForVar {
kf'=%]9#_T [font="Times]public static void main(String args[]) {
djfU:$!j& [font="Times]int i;
>9MS"t [font="Times]boolean done = false;
I3PQdAs~&h [font="Times]i = 0;
\f<z*!,D$ [font="Times]for( ; !done; ) {
&Q~)]|t [font="Times]System.out.println("i is " + i);
UhdqY] [font="Times]if(i == 10) done = true;
G1/Gq.< [font="Times]i++;
.zIgbv s [font="Times]}
m
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/S[?{Q A [font="Times]}
循环语句的例子下载 - zQ<ZE [font="Times] 2.分支语句[font="Times]
A$:|Qd7F1 [font="Times] if/else语句
b Ob
Nc [font="Times]class IfElse {
!?b/-~o7S [font="Times]public static void main(String args[]) {
ki#bPgT [font="Times]int month = 4; // April
WGPD8. [font="Times]String season;
J)KnE2dw5 [font="Times]if(month == 12 || month == 1 || month == 2)
;Gh>44UM[ [font="Times]season = "Winter";
{:$NfW [font="Times]else if(month == 3 || month == 4 || month == 5)
=W<[Fe3 [font="Times]season = "Spring";
tH,sql) [font="Times]else if(month == 6 || month == 7 || month == 8)
B$j' /e-Zk [font="Times]season = "Summer";
h;nQxmJ9 [font="Times]else if(month == 9 || month == 10 || month == 11)
0#^Bf[Dn [font="Times]season = "Autumn";
,Y-S( [font="Times]else
[4: Yi{> [font="Times]season = "Bogus Month";
q~M2:SN@X [font="Times]System.out.println("April is in the " + season + ".");
C99&L3bz^( [font="Times]}
%{"dP%|w4} [font="Times]}
kIX)oD}c [font="Times]//这段程序输出[font="Times]:
86qcf"?E [font="Times]//April is in the Spring.
6bUl>4 [font="Times]// 注意[font="Times] “[font="Times]||”是或运算
bS%C?8 [font="Times] switch语句
tpGCrn2w> [font="Times] class Switch {
%I0}4$ [font="Times]public static void main(String args[]) {
v^TkDf(Oz [font="Times]int month = 4;
e[8UH =`| [font="Times]String season;
1yS&~
y?a [font="Times]switch (month) {
V)h
y0_ [font="Times]case 12:
~
aA;<# [font="Times]case 1:
t#~XLCE [font="Times]case 2:
_*n)mlLln [font="Times]season = "Winter";
e=L*&X [font="Times]break;
\XDmK [font="Times]case 3:
[8z&-'J= [font="Times]case 4:
H?{MRe [font="Times]case 5:
a'A s [font="Times]season = "Spring";
JnHNkCaU [font="Times]break;
c=aO5(i0 [font="Times]case 6:
xl,ryc3J [font="Times]case 7:
m1V- %kUI [font="Times]case 8:
$
9 =8@ [font="Times]season = "Summer";
d"GDZ[6 [font="Times]break;
?Sw /(}|m [font="Times]case 9:
GV>&g [font="Times]case 10:
#R<G,"N5 [font="Times]case 11:
R[Nbtbv9Q [font="Times]season = "Autumn";
5*1#jiq [font="Times]break;
61>f(?s [font="Times]default:
%qi%$ [font="Times]season = "Bogus Month";
`;/XK,m- [font="Times]}
O5OXw] [font="Times]System.out.println("April is in the " + season + ".");
`I#`:hj [font="Times]}
(
OXY^iq [font="Times]}
分支语句代码下载 ,5.
<oDH >f%, `r [font="Times]switch语句适合于条件非常多的逻辑
.pW o >`" 请看上述语句可以混合使用,请看
下载例子