全新java初学者实践教程6(Java SE5.0版)
#"f'7'TE 基本语法3
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P*K <J{'o`{ I+;-p]~ 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:
L%cVykWY" vqNsZ 8|` [font="Times] 1.循环语句[font="Times]:while,do-while,for
5#2F1NX jC, FG'P [font="Times]2.分支语句[font="Times]:if-else,switch,
G|u3UhyB [font="Times]
csQfic 3.跳转语句[font="Times] break,continue,label: 和[font="Times]return
xWX*tJ4 [font="Times]
eon!CE0 4.异常处理语句[font="Times]:try-catch-finally,throw
AuiFbRFi S h4wqf 实践:
vO@s$qi [font="Times] 1.循环语句
-kj< 1~YW [font="Times] while 语句
b~0N^p[&% [font="Times]class While {
r)T[(D'Tm- [font="Times]public static void main(String args[]) {
zO=%J)-= [font="Times]int n = 10;
2eP;[o [font="Times]while(n > 0) {
d"Q |I [font="Times]System.out.println("tick " + n);
xN"Z1n7t [font="Times]n--;
NPjv)TN}3 [font="Times]}
SUtf[6 [font="Times]}
0$vj!-Mb^j [font="Times]}
E~hzh /,34 [font="Times] do…while 语句
slW3qRT\k [font="Times] class DoWhile {
Mi7y&~, [font="Times]public static void main(String args[]) {
(ywo
a [font="Times]int n = 10;
#-#NqX: [font="Times]do {
!1sU>Xb4J [font="Times]System.out.println("tick " + n);
.ln8|;% [font="Times]n--;
5#JJ? [font="Times]} while(n > 0);
;/8 {N0 [font="Times]}
[=TCEU{"~ [font="Times]}
eE]hy'{d< 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。
Om'(mr [font="Times] for语句
v3RcwySk [font="Times] class ForTick {
V5rp.~ [font="Times]public static void main(String args[]) {
^]c6RE_ [font="Times]int n;
tj1JB% [font="Times]for(n=10; n>0; n--)
qr(`&hB-L [font="Times]System.out.println("tick " + n);
4? (W%? [font="Times]}
8;\sU?
[font="Times]}
g!J0L7i| 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。
/Z%>ArAx 还有啊,[font="Times]for循环的部分可以为空的
I!: z,t< [font="Times]class ForVar {
NCS!:d:Ry [font="Times]public static void main(String args[]) {
y2yKm1<Ru< [font="Times]int i;
"^CXY3v [font="Times]boolean done = false;
bE\,}DTy [font="Times]i = 0;
eiMH['X5 [font="Times]for( ; !done; ) {
6[dur'x [font="Times]System.out.println("i is " + i);
,^s [font="Times]if(i == 10) done = true;
u5E]t9~Pq [font="Times]i++;
Rm>^tu
- [font="Times]}
E;(Rm>lB [font="Times]}
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循环语句的例子下载 ;?L\Fz(< [font="Times] 2.分支语句[font="Times]
3:CO{=`\7B [font="Times] if/else语句
pBJAaCGm [font="Times]class IfElse {
~oD8Rnf [font="Times]public static void main(String args[]) {
SW?p?< [font="Times]int month = 4; // April
E
l&h;N [font="Times]String season;
.p6+l!" [font="Times]if(month == 12 || month == 1 || month == 2)
9s$U%F6} [font="Times]season = "Winter";
a}nbo4jK [font="Times]else if(month == 3 || month == 4 || month == 5)
Y:QD [font="Times]season = "Spring";
-=}3j&,\R [font="Times]else if(month == 6 || month == 7 || month == 8)
`)>7)={ [font="Times]season = "Summer";
:
mGAt[Cc [font="Times]else if(month == 9 || month == 10 || month == 11)
'/%zi,0 [font="Times]season = "Autumn";
UVuDQ [font="Times]else
)mcEQ -!b [font="Times]season = "Bogus Month";
^>$P)=O:v [font="Times]System.out.println("April is in the " + season + ".");
]F*3"y?)2 [font="Times]}
<,%:
[font="Times]}
`iG,H[t+j [font="Times]//这段程序输出[font="Times]:
VM=+afY5M [font="Times]//April is in the Spring.
D&:yMp( [font="Times]// 注意[font="Times] “[font="Times]||”是或运算
o4^Fo p [font="Times] switch语句
@e2}BhB2 [font="Times] class Switch {
NYB[Zyp [font="Times]public static void main(String args[]) {
12`_;[37 [font="Times]int month = 4;
'3(l-nPiG^ [font="Times]String season;
\ZXLX'- [font="Times]switch (month) {
7*H:Ob)9k [font="Times]case 12:
x8#ODuH [font="Times]case 1:
SAv<& [font="Times]case 2:
773/#c [font="Times]season = "Winter";
{bNXedZ\ [font="Times]break;
JWO=!^ [font="Times]case 3:
$.mQ7XDA9 [font="Times]case 4:
TYgQJW? [font="Times]case 5:
|$lwkC)O [font="Times]season = "Spring";
u:gtOjk2 [font="Times]break;
e]>ori
8 [font="Times]case 6:
3/6/G}s [font="Times]case 7:
ZU2laqa_ [font="Times]case 8:
A2H4k|8 [font="Times]season = "Summer";
g[z.*y/ [font="Times]break;
-7]Xjb5 [font="Times]case 9:
:VA.Q rKW [font="Times]case 10:
~%y @Xsot> [font="Times]case 11:
_GtBP'iN [font="Times]season = "Autumn";
#
'|'r+ [font="Times]break;
B5am1y{P# [font="Times]default:
.V'V:;BE% [font="Times]season = "Bogus Month";
A7XnHPIw [font="Times]}
H}0dd" [font="Times]System.out.println("April is in the " + season + ".");
u=+q$Q] [font="Times]}
,w)p"[^b [font="Times]}
分支语句代码下载 ,d,\-x-+/ f^Bc [font="Times]switch语句适合于条件非常多的逻辑
'Pltn{iq[ 请看上述语句可以混合使用,请看
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