全新java初学者实践教程6(Java SE5.0版)
x 4</\o 基本语法3
u/c3omY"# ]Hy PJ ]/Qy1, 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:
MwqT`;lb a[g|APZz [font="Times] 1.循环语句[font="Times]:while,do-while,for
CZRo{2!?U \Egc5{ [font="Times]2.分支语句[font="Times]:if-else,switch,
(v:ek_ [font="Times]
ja- ~` 3.跳转语句[font="Times] break,continue,label: 和[font="Times]return
b_Jq=Gk` [font="Times]
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4.异常处理语句[font="Times]:try-catch-finally,throw
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BH1J]_ 实践:
S{T d/1} [font="Times] 1.循环语句
jY+S,lD [font="Times] while 语句
yKEFne8^ [font="Times]class While {
hyfnIb@~} [font="Times]public static void main(String args[]) {
PZRn6Tc [font="Times]int n = 10;
.{a2z*o [font="Times]while(n > 0) {
bK8F | [font="Times]System.out.println("tick " + n);
r Ob"S* [font="Times]n--;
:yjK*"T|OD [font="Times]}
ZCFf@2&z8 [font="Times]}
eSNSnh]' [font="Times]}
xcvr D [font="Times] do…while 语句
'#PqI)P [font="Times] class DoWhile {
wKS-O%? [font="Times]public static void main(String args[]) {
gam#6
s [font="Times]int n = 10;
Y*cJ4hQ [font="Times]do {
>-5Gt [font="Times]System.out.println("tick " + n);
SuH.lCF-g [font="Times]n--;
/
&D$kxz [font="Times]} while(n > 0);
\R\@t]>Y [font="Times]}
L2.`1Aag [font="Times]}
D#Yx,`Ui 二者区别,[font="Times]do…while至少循环一次,而[font="Times]while的表达式要是为[font="Times]flase的话可以一次也不循环。再通俗一点,[font="Times]do…while就算是括号里的是[font="Times]flase,人家最少也能[font="Times]do一次。
Ij}F<ZgZG [font="Times] for语句
(e3Gs+; [font="Times] class ForTick {
TT ZxkK [font="Times]public static void main(String args[]) {
;GFB@I@
[font="Times]int n;
)(Mr f{ [font="Times]for(n=10; n>0; n--)
x>,F*3d3 [font="Times]System.out.println("tick " + n);
]'!xc9KGR [font="Times]}
83ic@[ [font="Times]}
S50x0$%<W 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。
I
cR;A\z 还有啊,[font="Times]for循环的部分可以为空的
h`h>H
X [font="Times]class ForVar {
k7|z$=zY [font="Times]public static void main(String args[]) {
G h[`q7B
Q [font="Times]int i;
oA;Ty7s [font="Times]boolean done = false;
^h6$>n5 [font="Times]i = 0;
W({TC [font="Times]for( ; !done; ) {
H4'DL'83 [font="Times]System.out.println("i is " + i);
''OInfd? [font="Times]if(i == 10) done = true;
wYO"znd [font="Times]i++;
b}Hl$V(uD [font="Times]}
}i7U}T [font="Times]}
G k"L%Zt) [font="Times]}
循环语句的例子下载 v<3o[m q [font="Times] 2.分支语句[font="Times]
Hn9F
gul& [font="Times] if/else语句
h>Uid
&:? [font="Times]class IfElse {
vo6[2.HS [font="Times]public static void main(String args[]) {
o47 f [font="Times]int month = 4; // April
^Z>B/aJq [font="Times]String season;
xPDA475Cw3 [font="Times]if(month == 12 || month == 1 || month == 2)
F\=Rm [font="Times]season = "Winter";
Vx6?@R [font="Times]else if(month == 3 || month == 4 || month == 5)
fHe0W [font="Times]season = "Spring";
FL#g9U> [font="Times]else if(month == 6 || month == 7 || month == 8)
(ND5CKCR^ [font="Times]season = "Summer";
r3H}*Wpf [font="Times]else if(month == 9 || month == 10 || month == 11)
^/C$L8# [font="Times]season = "Autumn";
1 73<x){ [font="Times]else
Go\} A:|s [font="Times]season = "Bogus Month";
Z#F,y)YiO [font="Times]System.out.println("April is in the " + season + ".");
of'ZNQ/ [font="Times]}
!q$&JZY [font="Times]}
jxnQG A [font="Times]//这段程序输出[font="Times]:
En,)}yI [font="Times]//April is in the Spring.
^\[LrPqe [font="Times]// 注意[font="Times] “[font="Times]||”是或运算
12tJrS*Z [font="Times] switch语句
nRXSW&V"m [font="Times] class Switch {
kUg+I_j6* [font="Times]public static void main(String args[]) {
UGmuX:@y76 [font="Times]int month = 4;
:qAc= IC% [font="Times]String season;
k)5_1 y [font="Times]switch (month) {
_iGU|$a [font="Times]case 12:
iL0jpa<} [font="Times]case 1:
O[(?.9 [font="Times]case 2:
RF4$ [font="Times]season = "Winter";
\U!@OX.R'M [font="Times]break;
Ac[|MBaF [font="Times]case 3:
d2A
wvP [font="Times]case 4:
I>H;o{X# [font="Times]case 5:
%|*nmIPq( [font="Times]season = "Spring";
?{"XrQw [font="Times]break;
VqD[G<|9T [font="Times]case 6:
P^8^1-b [font="Times]case 7:
V/3 {^Fcr [font="Times]case 8:
b$?Xn {Y [font="Times]season = "Summer";
.lvI8Jf~X [font="Times]break;
uS,p|}Q& [font="Times]case 9:
rmPne8D=c( [font="Times]case 10:
lk[G;=K:. [font="Times]case 11:
/i{tS`[F2a [font="Times]season = "Autumn";
~IlF*Zz#}6 [font="Times]break;
oI_oz0nHk [font="Times]default:
-v;n"Zy1 [font="Times]season = "Bogus Month";
aJ6#=G61l [font="Times]}
s-C!uq [font="Times]System.out.println("April is in the " + season + ".");
cXk6e.Uz [font="Times]}
llHc=&y# [font="Times]}
分支语句代码下载 .Na&I)udX. S9HBr [font="Times]switch语句适合于条件非常多的逻辑
-}Cc"qm 请看上述语句可以混合使用,请看
下载例子