全新java初学者实践教程6(Java SE5.0版)
9yla &XTD 基本语法3
<y4hK3wP r6_g/7.- 66ULR&D8 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:
h`Ld%iN\ =^a Ngq [font="Times] 1.循环语句[font="Times]:while,do-while,for
B?A]0S ')eg6IC0&T [font="Times]2.分支语句[font="Times]:if-else,switch,
NVyel*QE [font="Times]
'Lm\ r+$F 3.跳转语句[font="Times] break,continue,label: 和[font="Times]return
~4-:;8a [font="Times]
rjk{9u1a" 4.异常处理语句[font="Times]:try-catch-finally,throw
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FYe#x]ue 实践:
\PU7,*2 [font="Times] 1.循环语句
)>-94xx| [font="Times] while 语句
!q]@/<= [font="Times]class While {
Zw@=WW[Q`p [font="Times]public static void main(String args[]) {
::<v; `l [font="Times]int n = 10;
M/?*?B [font="Times]while(n > 0) {
dV/ ^@[ [font="Times]System.out.println("tick " + n);
NgI n\)
=0 [font="Times]n--;
/O`<?aP% [font="Times]}
P]h-**O [font="Times]}
mCb1^Y [font="Times]}
/9QC$Z):< [font="Times] do…while 语句
I
\Luw*: [font="Times] class DoWhile {
1iLrKA [font="Times]public static void main(String args[]) {
Sm5T/&z [font="Times]int n = 10;
-d+o\qp"# [font="Times]do {
Al}D~6MD [font="Times]System.out.println("tick " + n);
@1c[<3xJT [font="Times]n--;
lEXER^6 [font="Times]} while(n > 0);
[H4)p ,R [font="Times]}
&m5FYm\ [font="Times]}
.X.,.vHx 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。
BmhIKXE{* [font="Times] for语句
woyn6Z1JQ [font="Times] class ForTick {
*!5X!\e_ [font="Times]public static void main(String args[]) {
$:}sm0; [font="Times]int n;
'nQQqx%v [font="Times]for(n=10; n>0; n--)
(qyT,K8 [font="Times]System.out.println("tick " + n);
_Dq,\} [font="Times]}
1`q>*S]( [font="Times]}
bc3 T8( 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。
goje4; 还有啊,[font="Times]for循环的部分可以为空的
-hU1wX%U [font="Times]class ForVar {
e8,!x9%J [font="Times]public static void main(String args[]) {
nhImO@Q: [font="Times]int i;
&P:2`\' [font="Times]boolean done = false;
v!WkPvU [font="Times]i = 0;
'UFPQ [font="Times]for( ; !done; ) {
:ceT8-PBRx [font="Times]System.out.println("i is " + i);
cOoF +hz0O [font="Times]if(i == 10) done = true;
`:*O8h~i^8 [font="Times]i++;
=yCz!vc [font="Times]}
\$Q? [font="Times]}
&6O0h0Vy [font="Times]}
循环语句的例子下载
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[font="Times] 2.分支语句[font="Times]
$ISx0l~ [font="Times] if/else语句
A$1Gc>C [font="Times]class IfElse {
d>gN3}tT [font="Times]public static void main(String args[]) {
XCyAt;neon [font="Times]int month = 4; // April
I7]qTS[vg [font="Times]String season;
S4C4_*~Vd [font="Times]if(month == 12 || month == 1 || month == 2)
j21>\K!p [font="Times]season = "Winter";
ZxoAf;U~ [font="Times]else if(month == 3 || month == 4 || month == 5)
c 4
bo [font="Times]season = "Spring";
h=o%\F4 [font="Times]else if(month == 6 || month == 7 || month == 8)
t2_pwd*B [font="Times]season = "Summer";
,8&ND864v [font="Times]else if(month == 9 || month == 10 || month == 11)
"NvB@>S [font="Times]season = "Autumn";
<!a%GI [font="Times]else
,/Al' [font="Times]season = "Bogus Month";
]&_z@Z.i [font="Times]System.out.println("April is in the " + season + ".");
2*pNIc [font="Times]}
/#Lm)-%G [font="Times]}
?656P=b) [font="Times]//这段程序输出[font="Times]:
"}^}3"/. [font="Times]//April is in the Spring.
jn._4TQ*} [font="Times]// 注意[font="Times] “[font="Times]||”是或运算
6QX2&[qWS [font="Times] switch语句
c+N\uG4 [font="Times] class Switch {
\qw1\-q [font="Times]public static void main(String args[]) {
/c!@ H(^) [font="Times]int month = 4;
V7)<MY [font="Times]String season;
il~A(`+YO [font="Times]switch (month) {
%mNd9 ]< [font="Times]case 12:
8],tGMu [font="Times]case 1:
NxrfRhaU3 [font="Times]case 2:
0I7 r{T [font="Times]season = "Winter";
i/j eb*d0 [font="Times]break;
q 1~3T;Il [font="Times]case 3:
m/p:W/0L [font="Times]case 4:
!CUX13/0 [font="Times]case 5:
EeDK ^W8N [font="Times]season = "Spring";
a]t| /Mq [font="Times]break;
n}3fItSJ [font="Times]case 6:
>*"1`vcxF [font="Times]case 7:
m:]60koz]o [font="Times]case 8:
Fm`c [font="Times]season = "Summer";
yv2wQ_({ [font="Times]break;
8?G534*r@2 [font="Times]case 9:
T3In0LQ [font="Times]case 10:
R:,
|xz [font="Times]case 11:
li [font="Times]season = "Autumn";
eK =v<X [font="Times]break;
`FRdo [font="Times]default:
W3]?>sLE* [font="Times]season = "Bogus Month";
cb`ik)=K% [font="Times]}
9k3RC}dEr [font="Times]System.out.println("April is in the " + season + ".");
n|) JhXQ [font="Times]}
nrJW.F]S8[ [font="Times]}
分支语句代码下载 qV:TuR-|w yBnUz" [font="Times]switch语句适合于条件非常多的逻辑
#8i9@w 请看上述语句可以混合使用,请看
下载例子