全新java初学者实践教程6(Java SE5.0版)
#q[k"x=c 基本语法3
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%7 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:
8SJi~gV j?5s/ [font="Times] 1.循环语句[font="Times]:while,do-while,for
C(t>ZR }ioHSkCD [font="Times]2.分支语句[font="Times]:if-else,switch,
g\Ck!KJ/y [font="Times]
-+#QZ7b 3.跳转语句[font="Times] break,continue,label: 和[font="Times]return
Vh%=JL
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Lm-yTMNPn 4.异常处理语句[font="Times]:try-catch-finally,throw
FZUN*5` w_O3]; 实践:
ynWF Y<VX [font="Times] 1.循环语句
ukZ>_ke`+ [font="Times] while 语句
G-vBJlt=t [font="Times]class While {
vMDX [font="Times]public static void main(String args[]) {
TB!z:n [font="Times]int n = 10;
_[eAA4h [font="Times]while(n > 0) {
;r**`O [font="Times]System.out.println("tick " + n);
,-55*Rb i [font="Times]n--;
3,x|w [font="Times]}
nhbCk6Y5LZ [font="Times]}
WyO7,Qr\ [font="Times]}
0N" VOEvG [font="Times] do…while 语句
DH3.4EUWS [font="Times] class DoWhile {
:P!"'&gCL [font="Times]public static void main(String args[]) {
7U:-zfq [font="Times]int n = 10;
O@[jNs)]. [font="Times]do {
F@+FXnz [font="Times]System.out.println("tick " + n);
{
S]"-x [font="Times]n--;
tH7@oV; [font="Times]} while(n > 0);
-F7GUB6B [font="Times]}
WAzYnl'p [font="Times]}
=.*+c\ 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。
`^mPq?f [font="Times] for语句
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[font="Times] class ForTick {
@raw8w\Zj+ [font="Times]public static void main(String args[]) {
@W{VT7w [font="Times]int n;
&}YJ"o[I [font="Times]for(n=10; n>0; n--)
Py&DnG'H [font="Times]System.out.println("tick " + n);
'G6M:IXno [font="Times]}
dtXAEL\q [font="Times]}
mX4u#$xs: 与上面那两个的区别,[font="Times]for循环执行的次数是可以在执行之前确定的。通俗一点说吧,看这个例子[font="Times] for(n=10; n>0; n--)就是在括号里的时候,就已经知道要循环[font="Times]10次了。
Z= 'DV1A$, 还有啊,[font="Times]for循环的部分可以为空的
"ggViIOw& [font="Times]class ForVar {
2HxT+|~d6 [font="Times]public static void main(String args[]) {
88K=jo))b [font="Times]int i;
?1DA [font="Times]boolean done = false;
s>pOfXIx [font="Times]i = 0;
,3m]jp' [font="Times]for( ; !done; ) {
IvW%n(a8^ [font="Times]System.out.println("i is " + i);
LjE@[@d [font="Times]if(i == 10) done = true;
U\crp
T` [font="Times]i++;
aJQx"6c? [font="Times]}
Z#J
cNquM [font="Times]}
~+JEl% [font="Times]}
循环语句的例子下载 XAn{xNpz [font="Times] 2.分支语句[font="Times]
ucVWvXCr [font="Times] if/else语句
qIO<\Yl [font="Times]class IfElse {
s,tZi6Z=%E [font="Times]public static void main(String args[]) {
] bPj%sb*@ [font="Times]int month = 4; // April
1XwW4cZ>: [font="Times]String season;
]VYv>o`2 [font="Times]if(month == 12 || month == 1 || month == 2)
R')D~JJ<8a [font="Times]season = "Winter";
O%w"bEr)N [font="Times]else if(month == 3 || month == 4 || month == 5)
UG]]Vk1d] [font="Times]season = "Spring";
|=dmxfj@ [font="Times]else if(month == 6 || month == 7 || month == 8)
d]kP@flOV [font="Times]season = "Summer";
p1-bq: [font="Times]else if(month == 9 || month == 10 || month == 11)
AU3Ou5 [font="Times]season = "Autumn";
u{H'evv0O [font="Times]else
=p1aF/1$I [font="Times]season = "Bogus Month";
zF%'~S0{ [font="Times]System.out.println("April is in the " + season + ".");
Ql%0%naq1 [font="Times]}
h{$mL#J [font="Times]}
Vy+%sG
q" [font="Times]//这段程序输出[font="Times]:
4 ^=qc99 [font="Times]//April is in the Spring.
|GDf<\ [font="Times]// 注意[font="Times] “[font="Times]||”是或运算
SkmL X@:( [font="Times] switch语句
(c'=jJX [font="Times] class Switch {
`|["{j}^ [font="Times]public static void main(String args[]) {
_fVC\18T [font="Times]int month = 4;
e)(m0m\ [font="Times]String season;
B/iRR2h [font="Times]switch (month) {
^KBE2C [font="Times]case 12:
zW,Nv>Ac5 [font="Times]case 1:
%(9BWO [font="Times]case 2:
wFgL\[$^| [font="Times]season = "Winter";
SP&Y|I$: [font="Times]break;
3Zr'Mn [font="Times]case 3:
qrWeV8ur+ [font="Times]case 4:
Z5oX "Yx [font="Times]case 5:
.U66Uet>RX [font="Times]season = "Spring";
`I\)Kk@*b9 [font="Times]break;
ZL0':7 [font="Times]case 6:
x[ sSM: [font="Times]case 7:
K2W$I H:. [font="Times]case 8:
=:|fN3nJ2 [font="Times]season = "Summer";
!hBzT7CO [font="Times]break;
__FhuP P [font="Times]case 9:
;}=4z^^5 [font="Times]case 10:
qtx5N)J6 [font="Times]case 11:
z_Nw%V4kr [font="Times]season = "Autumn";
U%Igj:%?;` [font="Times]break;
RWN2P6 [font="Times]default:
#ny&bJj [font="Times]season = "Bogus Month";
np>RxiB^ [font="Times]}
<hYrcOt [font="Times]System.out.println("April is in the " + season + ".");
c]pO'6] [font="Times]}
+npcU:(Kg [font="Times]}
分支语句代码下载 _?5$ST@5 2'R&K [font="Times]switch语句适合于条件非常多的逻辑
EmaVd+Sw 请看上述语句可以混合使用,请看
下载例子