全新java初学者实践教程6(Java SE5.0版)
[P+kQBLpL 基本语法3
HXU#Ux ,cNe-KJk
rp4D_80q 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:
i F+:j8
b !+eU [font="Times] 1.循环语句[font="Times]:while,do-while,for
!K( X|a{Z*y;r* [font="Times]2.分支语句[font="Times]:if-else,switch,
q~}oU5 [font="Times]
R5ra*!|L) 3.跳转语句[font="Times] break,continue,label: 和[font="Times]return
~2k.x*$ [font="Times]
2H%lN` 4.异常处理语句[font="Times]:try-catch-finally,throw
,y]-z8J v)Y)tu> 实践:
K@7%i|H [font="Times] 1.循环语句
U*~-\jN1pb [font="Times] while 语句
,
@jtD*c) [font="Times]class While {
DujVV(+I [font="Times]public static void main(String args[]) {
LG:k}z/T [font="Times]int n = 10;
mI7lv;oN<5 [font="Times]while(n > 0) {
6]iU-k0b [font="Times]System.out.println("tick " + n);
W+a/>U [font="Times]n--;
#HgNwM [font="Times]}
"Vq=
Ph [font="Times]}
J>v[5FX+ [font="Times]}
Md~SzrU [font="Times] do…while 语句
Z|C,HF+m. [font="Times] class DoWhile {
+UDt2 [font="Times]public static void main(String args[]) {
~Y`ys[Z m [font="Times]int n = 10;
Ibz9juY [font="Times]do {
yo[Sh6r/9b [font="Times]System.out.println("tick " + n);
|^-D&C(Eu [font="Times]n--;
7nT|yL? [font="Times]} while(n > 0);
`+n0a@BVB [font="Times]}
4 *}H3-` [font="Times]}
vCi`htm% 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。
/ ]8e[t>!f [font="Times] for语句
?TpjU*Cxy [font="Times] class ForTick {
2FuV%\p [font="Times]public static void main(String args[]) {
=W7-;& [font="Times]int n;
h|]cZMGo [font="Times]for(n=10; n>0; n--)
OpaRQ= [font="Times]System.out.println("tick " + n);
:j`f%Vg~x [font="Times]}
h"ZIh= j@ [font="Times]}
_{`Z?lt 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。
>s5}pkAv|e 还有啊,[font="Times]for循环的部分可以为空的
=J1V?x=l@ [font="Times]class ForVar {
pK-tj [font="Times]public static void main(String args[]) {
z@VL?A(3 [font="Times]int i;
x[lIib1s [font="Times]boolean done = false;
_6fy'%J=U [font="Times]i = 0;
^5s7mls [font="Times]for( ; !done; ) {
`n>|rd [font="Times]System.out.println("i is " + i);
\'Ca1[y@B [font="Times]if(i == 10) done = true;
HK :K~h [font="Times]i++;
lPR^~&/ [font="Times]}
KS8@A/f [font="Times]}
SY5}Bu# [font="Times]}
循环语句的例子下载 (xW+* % [font="Times] 2.分支语句[font="Times]
=u}~\ 'd [font="Times] if/else语句
nT> v [font="Times]class IfElse {
ke2dQ^kc4 [font="Times]public static void main(String args[]) {
9xbT?$^ [font="Times]int month = 4; // April
:jv(-RTI [font="Times]String season;
L'Cd`.yVO [font="Times]if(month == 12 || month == 1 || month == 2)
A4,%l\di< [font="Times]season = "Winter";
BlpyE[h
T [font="Times]else if(month == 3 || month == 4 || month == 5)
r5xm7- `c [font="Times]season = "Spring";
X`_tm3HC [font="Times]else if(month == 6 || month == 7 || month == 8)
5[)5K?% [font="Times]season = "Summer";
8|@) #: [font="Times]else if(month == 9 || month == 10 || month == 11)
jv.tg,c _6 [font="Times]season = "Autumn";
vk
E]$4P[$ [font="Times]else
[[c0g6 [font="Times]season = "Bogus Month";
0]5XTc3r [font="Times]System.out.println("April is in the " + season + ".");
jfK&CA [font="Times]}
,iYhD-"' [font="Times]}
>rlUV"8jY; [font="Times]//这段程序输出[font="Times]:
R=.?el [font="Times]//April is in the Spring.
xY]q[a?cy [font="Times]// 注意[font="Times] “[font="Times]||”是或运算
9^DAlY,x. [font="Times] switch语句
1Z
~C3)T= [font="Times] class Switch {
?jz\[0)s [font="Times]public static void main(String args[]) {
WD\Yx~o [font="Times]int month = 4;
>N al\ [font="Times]String season;
_yAY5TIv [font="Times]switch (month) {
T/ ECW [font="Times]case 12:
MUbKlX [font="Times]case 1:
zlP{1z;nV [font="Times]case 2:
<O=0 ^V [font="Times]season = "Winter";
l|
uiC%T [font="Times]break;
Rw
`ezC# [font="Times]case 3:
Wi=zu[[qc [font="Times]case 4:
mTsyVji8 [font="Times]case 5:
[_%u5sc-y [font="Times]season = "Spring";
X~&8^? [font="Times]break;
Vj4 h#NN$ [font="Times]case 6:
G0!6rDu2, [font="Times]case 7:
Jf4`
2KN\ [font="Times]case 8:
DNZ,rL:h [font="Times]season = "Summer";
b4wT3 [font="Times]break;
445JOP [font="Times]case 9:
_*UI}JtlS [font="Times]case 10:
:q3w;B~ [font="Times]case 11:
B`)sc ~u [font="Times]season = "Autumn";
!2Ompcr1 [font="Times]break;
mC@v," [font="Times]default:
H0&wn#);6R [font="Times]season = "Bogus Month";
*~GI-h [font="Times]}
=c\(]xX [font="Times]System.out.println("April is in the " + season + ".");
f|(9+~K/7& [font="Times]}
kntY2FM [font="Times]}
分支语句代码下载 J>#hu3&UOQ ~x(|'` [font="Times]switch语句适合于条件非常多的逻辑
@8{8|P 请看上述语句可以混合使用,请看
下载例子