全新java初学者实践教程6(Java SE5.0版)
NQG"}=KA 基本语法3
wb}tN7~Y; so7;h$h!H J: LSGj;R 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:
L6a8%%` 1jL?z6S [font="Times] 1.循环语句[font="Times]:while,do-while,for
$3L7R f_7p.H6\ [font="Times]2.分支语句[font="Times]:if-else,switch,
G<-.{Gx) [font="Times]
Bg`b*(Q 3.跳转语句[font="Times] break,continue,label: 和[font="Times]return
3
*G=U [font="Times]
gDsZbmR 4.异常处理语句[font="Times]:try-catch-finally,throw
#xc[)Y,W c|7Pnx%gT 实践:
MiC&av [font="Times] 1.循环语句
z'fS%uI [font="Times] while 语句
O!g>
f [font="Times]class While {
3t,SXI@ [font="Times]public static void main(String args[]) {
SBEJ@&iB~ [font="Times]int n = 10;
&^<94l [font="Times]while(n > 0) {
4Mprc~ 7vr [font="Times]System.out.println("tick " + n);
O/k4W# [font="Times]n--;
C.@zVt [font="Times]}
mNV4"lNR [font="Times]}
y{kXd1, [font="Times]}
Y \j &84 [font="Times] do…while 语句
L:'Y#VI{ [font="Times] class DoWhile {
( /uL6W d0 [font="Times]public static void main(String args[]) {
<@Ew-JU [font="Times]int n = 10;
~L?p/3m [font="Times]do {
4I,HvP [font="Times]System.out.println("tick " + n);
$-o 39A# [font="Times]n--;
y_J{+ [font="Times]} while(n > 0);
5|AZ/!rb [font="Times]}
1-q\C<Q) [font="Times]}
vnIxI a 二者区别,[font="Times]do…while至少循环一次,而[font="Times]while的表达式要是为[font="Times]flase的话可以一次也不循环。再通俗一点,[font="Times]do…while就算是括号里的是[font="Times]flase,人家最少也能[font="Times]do一次。
gAR];(* [font="Times] for语句
+L_.XToq- [font="Times] class ForTick {
@ cv`}k [font="Times]public static void main(String args[]) {
SLBKXj| [font="Times]int n;
5ptbz<Xv [font="Times]for(n=10; n>0; n--)
Z5NuLB' [font="Times]System.out.println("tick " + n);
<01MXT- [font="Times]}
I</Nmgf [font="Times]}
B [y1RI|9 与上面那两个的区别,[font="Times]for循环执行的次数是可以在执行之前确定的。通俗一点说吧,看这个例子[font="Times] for(n=10; n>0; n--)就是在括号里的时候,就已经知道要循环[font="Times]10次了。
hf%W grO. 还有啊,[font="Times]for循环的部分可以为空的
p-ry{"XA [font="Times]class ForVar {
4N*^% [font="Times]public static void main(String args[]) {
Wlt shZo [font="Times]int i;
dU+1@_ [font="Times]boolean done = false;
m.lNKIknQ [font="Times]i = 0;
6W3}6p [font="Times]for( ; !done; ) {
}LE.kd& [font="Times]System.out.println("i is " + i);
\*_qP*vq@ [font="Times]if(i == 10) done = true;
S$V'_ [font="Times]i++;
:<nL9y jt [font="Times]}
Av/|={i [font="Times]}
1no$|n# [font="Times]}
循环语句的例子下载 nar=\cs~g [font="Times] 2.分支语句[font="Times]
cbS8~Xmj [font="Times] if/else语句
]jM D'vg^b [font="Times]class IfElse {
KxiZx I [font="Times]public static void main(String args[]) {
M"~B_t,Nw [font="Times]int month = 4; // April
&0Nd9%> [font="Times]String season;
v3`J~,V< [font="Times]if(month == 12 || month == 1 || month == 2)
mQ1QJ_; [font="Times]season = "Winter";
d{DlW
|_ [font="Times]else if(month == 3 || month == 4 || month == 5)
[;};qQ-C2 [font="Times]season = "Spring";
]\Ez{MdAT [font="Times]else if(month == 6 || month == 7 || month == 8)
mz/KGZ5t [font="Times]season = "Summer";
LG51e7_gFi [font="Times]else if(month == 9 || month == 10 || month == 11)
n)
`4*d$` [font="Times]season = "Autumn";
6s>PZh [font="Times]else
Qza[~6 [font="Times]season = "Bogus Month";
|" l
g4S% [font="Times]System.out.println("April is in the " + season + ".");
hXYVi6(k [font="Times]}
<;W4Th<4 [font="Times]}
(A"oMnjWd [font="Times]//这段程序输出[font="Times]:
vW~_+:),e [font="Times]//April is in the Spring.
mb?yG:L=0b [font="Times]// 注意[font="Times] “[font="Times]||”是或运算
HaLEQ73 [font="Times] switch语句
#r0A<+t{T [font="Times] class Switch {
[_b10Z'{ [font="Times]public static void main(String args[]) {
SkN^ytKE [font="Times]int month = 4;
E6BW&Xp [font="Times]String season;
vUj7rDT| [font="Times]switch (month) {
!$Mv)c/_u [font="Times]case 12:
R'&^)_ [font="Times]case 1:
?ILNp`k [font="Times]case 2:
a'Aru^el [font="Times]season = "Winter";
~>)cY{wE_ [font="Times]break;
'0?5K0
2( [font="Times]case 3:
g"<kj" [font="Times]case 4:
\#~~,k
6f [font="Times]case 5:
gNe{P~ $= [font="Times]season = "Spring";
!L> 'g [font="Times]break;
R-Uj\M> [font="Times]case 6:
v]vrD2L [font="Times]case 7:
oSE'-8( [font="Times]case 8:
ISOPKZ#F [font="Times]season = "Summer";
T*LbZ"A [font="Times]break;
x4fLe5xv [font="Times]case 9:
|1rBK.8 [font="Times]case 10:
'gQm%:qU3r [font="Times]case 11:
Jg: Uv6eN+ [font="Times]season = "Autumn";
>uxak2nM- [font="Times]break;
vzy/Rq [font="Times]default:
IHf
A;&b [font="Times]season = "Bogus Month";
Ho*S>Y [font="Times]}
}|Cw]GW [font="Times]System.out.println("April is in the " + season + ".");
7?p%~j [font="Times]}
^oaG.)3 [font="Times]}
分支语句代码下载 NOo&5@z;H TlAY=JwW [font="Times]switch语句适合于条件非常多的逻辑
FVL0K(V( 请看上述语句可以混合使用,请看
下载例子