全新java初学者实践教程6(Java SE5.0版)
oTI*mGR1Z 基本语法3
20?i4h_ =_":Z!_ V2 VsJ 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:
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B%4V I J4"X#Q/ [font="Times] 1.循环语句[font="Times]:while,do-while,for
%-A8`lf< 2 )j\Lg_M [font="Times]2.分支语句[font="Times]:if-else,switch,
1.,mNY^UN [font="Times]
d`~#uN { 3.跳转语句[font="Times] break,continue,label: 和[font="Times]return
1xguG7 [font="Times]
!-.-!hBN 4.异常处理语句[font="Times]:try-catch-finally,throw
f{AgKW9" ,dVCbAS@ 实践:
(la<X<w [font="Times] 1.循环语句
sx]?^KR: [font="Times] while 语句
uTl:u [font="Times]class While {
/kw4":{] [font="Times]public static void main(String args[]) {
yN>"r2 [font="Times]int n = 10;
^OBaVb [font="Times]while(n > 0) {
On'3K+(_ [font="Times]System.out.println("tick " + n);
:ZL>JVk [font="Times]n--;
Vj2GK"$v [font="Times]}
r`;C9#jZ [font="Times]}
Z$ftG7;P0 [font="Times]}
g~B@=R [font="Times] do…while 语句
t*qA.xc6 [font="Times] class DoWhile {
vhL&az [font="Times]public static void main(String args[]) {
^F" *;8$ [font="Times]int n = 10;
G0Wd"AV+ [font="Times]do {
zl:
u@!' [font="Times]System.out.println("tick " + n);
\Flq8S /t^ [font="Times]n--;
Y43#]; [font="Times]} while(n > 0);
mlVv3mVyR< [font="Times]}
8fe"#^"s R [font="Times]}
e< CPaun 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。
"^XN"SUw [font="Times] for语句
Q}=RG//0* [font="Times] class ForTick {
3Aj_,&X.@( [font="Times]public static void main(String args[]) {
c%Gz{':+ [font="Times]int n;
eGTK^p [font="Times]for(n=10; n>0; n--)
8PEOi [font="Times]System.out.println("tick " + n);
gr fF\_[: [font="Times]}
1)YFEU&] [font="Times]}
J:(Shd'4D
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。
8^R>y 还有啊,[font="Times]for循环的部分可以为空的
8m1zL[.8g [font="Times]class ForVar {
> T-O3/KN [font="Times]public static void main(String args[]) {
,B#Y9[R [font="Times]int i;
^m+W [font="Times]boolean done = false;
,gOQIS56 [font="Times]i = 0;
;etQ [font="Times]for( ; !done; ) {
ttsB'|ps [font="Times]System.out.println("i is " + i);
8uT6Q C f [font="Times]if(i == 10) done = true;
.|aSGvE [font="Times]i++;
aJ}sYf^ [font="Times]}
pc.0;gN [font="Times]}
DY07?x7 [font="Times]}
循环语句的例子下载 O,>&w5 [font="Times] 2.分支语句[font="Times]
ks r5P~ [font="Times] if/else语句
#!5Nbe [font="Times]class IfElse {
Hug{9Hr3. [font="Times]public static void main(String args[]) {
7S1!|*/
I [font="Times]int month = 4; // April
kyjH~mK4 [font="Times]String season;
yBe/UFp+ [font="Times]if(month == 12 || month == 1 || month == 2)
_bd#C [font="Times]season = "Winter";
b@X@5SJFW [font="Times]else if(month == 3 || month == 4 || month == 5)
YpKai3 B [font="Times]season = "Spring";
d#d~t[= [font="Times]else if(month == 6 || month == 7 || month == 8)
E{6}'FG+A [font="Times]season = "Summer";
u]2k %TUY [font="Times]else if(month == 9 || month == 10 || month == 11)
[.Y=~)7FB [font="Times]season = "Autumn";
E, v1F! [font="Times]else
xsTxc&0^ [font="Times]season = "Bogus Month";
As\5Ze9| [font="Times]System.out.println("April is in the " + season + ".");
~Afs [font="Times]}
J6%op{7/ [font="Times]}
^KaMi_-- [font="Times]//这段程序输出[font="Times]:
Orb(xLChJ [font="Times]//April is in the Spring.
UA9LI<Y [font="Times]// 注意[font="Times] “[font="Times]||”是或运算
K$]QzPXS [font="Times] switch语句
zh.c_>jS [font="Times] class Switch {
lET)<V(Y [font="Times]public static void main(String args[]) {
P
X0#X=$ [font="Times]int month = 4;
}dHiW:J> [font="Times]String season;
u#,]>; [font="Times]switch (month) {
4bBxZY [font="Times]case 12:
:I$2[K [font="Times]case 1:
{S}@P~H= [font="Times]case 2:
Y o(B8}?0! [font="Times]season = "Winter";
i\Vpp8<B [font="Times]break;
NN:TT\!v [font="Times]case 3:
{DK:"ep [font="Times]case 4:
>YfOR%mS4 [font="Times]case 5:
L)+ eM&W [font="Times]season = "Spring";
bT8UmR98 [font="Times]break;
=_H39)|T [font="Times]case 6:
{
&'TA [font="Times]case 7:
@j
(jOe [font="Times]case 8:
#TWc` 8 [font="Times]season = "Summer";
nGbrWu]w [font="Times]break;
sy?>e*-{ [font="Times]case 9:
!kcg#+s91 [font="Times]case 10:
B1M/5cr. [font="Times]case 11:
FSmi.7 [font="Times]season = "Autumn";
@Y,F&8a$ [font="Times]break;
uqUo4z 5T [font="Times]default:
aOHCr>po, [font="Times]season = "Bogus Month";
,$]q2aL [font="Times]}
N 93E;B [font="Times]System.out.println("April is in the " + season + ".");
_tk5?9Ykn [font="Times]}
vck$@3* [font="Times]}
分支语句代码下载 )
G{v>Z, zoJ;5a.3B [font="Times]switch语句适合于条件非常多的逻辑
UIl_&| 请看上述语句可以混合使用,请看
下载例子