全新java初学者实践教程6(Java SE5.0版)
v:p} B$ 基本语法3
/=h` L, p'fYULYE "3hMq1NQ`g 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:
*A< 5*Db:F F?cK-. [font="Times] 1.循环语句[font="Times]:while,do-while,for
}Lv;! 9l,oP? [font="Times]2.分支语句[font="Times]:if-else,switch,
n(Uyz`qE [font="Times]
:4s1CC+@\ 3.跳转语句[font="Times] break,continue,label: 和[font="Times]return
_U0f=m [font="Times]
1}37Q&2 4.异常处理语句[font="Times]:try-catch-finally,throw
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cAy3^{3: 实践:
_6Ha [font="Times] 1.循环语句
9kojLqCT [font="Times] while 语句
7KPwQ?SjT [font="Times]class While {
3F0 N^)@ [font="Times]public static void main(String args[]) {
V1?]|HTQcT [font="Times]int n = 10;
G
j1_!.T [font="Times]while(n > 0) {
ca}2TT&t [font="Times]System.out.println("tick " + n);
-+5>|N# [font="Times]n--;
!c-*O<Y [font="Times]}
fV:83|eQ [font="Times]}
.o8t+X'G [font="Times]}
@6d[=!9 [font="Times] do…while 语句
iUwzs&frd [font="Times] class DoWhile {
m4& /s [font="Times]public static void main(String args[]) {
nie% eC&U [font="Times]int n = 10;
Wf<LR3 [font="Times]do {
fLVAKn [font="Times]System.out.println("tick " + n);
^GX)Z~ [font="Times]n--;
`kr?j:g [font="Times]} while(n > 0);
a>)f=uS [font="Times]}
w:l"\Tm [font="Times]}
P_dJZ((X 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。
nd(S3rct& [font="Times] for语句
.KC++\{HE [font="Times] class ForTick {
@H<q"-J [font="Times]public static void main(String args[]) {
U3kyraj [font="Times]int n;
7rPF$ \# [font="Times]for(n=10; n>0; n--)
8] ikygt" [font="Times]System.out.println("tick " + n);
J=L5=G7( [font="Times]}
'!$%> ||S [font="Times]}
H:G1BZjq 与上面那两个的区别,[font="Times]for循环执行的次数是可以在执行之前确定的。通俗一点说吧,看这个例子[font="Times] for(n=10; n>0; n--)就是在括号里的时候,就已经知道要循环[font="Times]10次了。
7Qsgys#/= 还有啊,[font="Times]for循环的部分可以为空的
L]Mo;kT<Q [font="Times]class ForVar {
Ewm9\qmg [font="Times]public static void main(String args[]) {
GF
WA>5n' [font="Times]int i;
s79r@])= [font="Times]boolean done = false;
y?0nI<}}HK [font="Times]i = 0;
<1%$Vq [font="Times]for( ; !done; ) {
&/b~k3{M_ [font="Times]System.out.println("i is " + i);
MPk5^ua: [font="Times]if(i == 10) done = true;
rs.M]8a2{& [font="Times]i++;
6^Sa; [font="Times]}
XlJZhc [font="Times]}
\?N2=jsu$ [font="Times]}
循环语句的例子下载 - YV>j [font="Times] 2.分支语句[font="Times]
@P"p+ [font="Times] if/else语句
G\?YK.Y> [font="Times]class IfElse {
"]iB6 [font="Times]public static void main(String args[]) {
fzA9'i` [font="Times]int month = 4; // April
X jX2] [font="Times]String season;
xKC[=E>z [font="Times]if(month == 12 || month == 1 || month == 2)
yEoV[K8k [font="Times]season = "Winter";
qCO/?kW [font="Times]else if(month == 3 || month == 4 || month == 5)
0;ji65 [font="Times]season = "Spring";
;6wA" [font="Times]else if(month == 6 || month == 7 || month == 8)
'QIqBU'~ [font="Times]season = "Summer";
n(|^SH4$b [font="Times]else if(month == 9 || month == 10 || month == 11)
%IRi1EmN8 [font="Times]season = "Autumn";
o]:9')5^ [font="Times]else
4&f3%eTi [font="Times]season = "Bogus Month";
0RK!/:' [font="Times]System.out.println("April is in the " + season + ".");
:@)>r9N [font="Times]}
]7mt[2Cd [font="Times]}
gdoLyxQ [font="Times]//这段程序输出[font="Times]:
3Y~>qGQwh [font="Times]//April is in the Spring.
9K&:V(gmw [font="Times]// 注意[font="Times] “[font="Times]||”是或运算
_? OG1t! [font="Times] switch语句
{GO#.P" [font="Times] class Switch {
MWL%
Bz [font="Times]public static void main(String args[]) {
9mFE?J [font="Times]int month = 4;
63A.@mL [font="Times]String season;
j)GtEP<n# [font="Times]switch (month) {
BSMwdr [font="Times]case 12:
V_:&S2j [font="Times]case 1:
c=+!>Z&i$G [font="Times]case 2:
)0R'(# [font="Times]season = "Winter";
\G3rX9xG [font="Times]break;
m9A!D [font="Times]case 3:
Bw{I;rW{2 [font="Times]case 4:
-GgA&dh [font="Times]case 5:
YDFyX){ [font="Times]season = "Spring";
"Yca%: [font="Times]break;
@]#1(9P [font="Times]case 6:
T n}s*<=V [font="Times]case 7:
j w9b) [font="Times]case 8:
\j)E5b+ [font="Times]season = "Summer";
I9Fr5p-%O [font="Times]break;
+KEWP\r [font="Times]case 9:
)tpL#J [font="Times]case 10:
i@BtM9: [font="Times]case 11:
QVE6We [font="Times]season = "Autumn";
nQ L@hc [font="Times]break;
(3&?w y_l [font="Times]default:
-)/$M(Pu" [font="Times]season = "Bogus Month";
FkRo
_? [font="Times]}
wuqJr:q*# [font="Times]System.out.println("April is in the " + season + ".");
&=k,?TJO> [font="Times]}
=kqt [font="Times]}
分支语句代码下载 X~i<g?] jZ3fKyp# [font="Times]switch语句适合于条件非常多的逻辑
Zsh9>]ML 请看上述语句可以混合使用,请看
下载例子