全新java初学者实践教程6(Java SE5.0版)
9jGu}Vo 基本语法3
8xMX NCD04U5y dgP3@`YS 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:
rSNi@; c[s4EUG [font="Times] 1.循环语句[font="Times]:while,do-while,for
wKY_Bo/d $Ygue5{c [font="Times]2.分支语句[font="Times]:if-else,switch,
*OQ2ucC8j [font="Times]
- !
S_ryL 3.跳转语句[font="Times] break,continue,label: 和[font="Times]return
f)<6 [font="Times]
%]7d`/ 4.异常处理语句[font="Times]:try-catch-finally,throw
2t1ZIyv3D Kf-JcBsrT 实践:
7x8
yxE [font="Times] 1.循环语句
|&4/n6;P$0 [font="Times] while 语句
fTX;.M/%
[font="Times]class While {
H0cA6I [font="Times]public static void main(String args[]) {
%SUQ9\SEs [font="Times]int n = 10;
bs1Rvx1:J% [font="Times]while(n > 0) {
;9'OOz|+1 [font="Times]System.out.println("tick " + n);
. 'yCw#f [font="Times]n--;
$`'/+x"% [font="Times]}
^/k*h J{ [font="Times]}
>5
BJ3Hf [font="Times]}
#,v{Ihn [font="Times] do…while 语句
Z #m+ObHK1 [font="Times] class DoWhile {
.o}v#W+st [font="Times]public static void main(String args[]) {
wS3'?PRX [font="Times]int n = 10;
,wPr"U+7 [font="Times]do {
~bpgSP" [font="Times]System.out.println("tick " + n);
r@,2E6xn [font="Times]n--;
]]Ufas9 [font="Times]} while(n > 0);
%N_%JK\{@ [font="Times]}
{f p[BF [font="Times]}
^dxTm1Z 二者区别,[font="Times]do…while至少循环一次,而[font="Times]while的表达式要是为[font="Times]flase的话可以一次也不循环。再通俗一点,[font="Times]do…while就算是括号里的是[font="Times]flase,人家最少也能[font="Times]do一次。
Wn}'bqp [font="Times] for语句
wUM0M?_p[ [font="Times] class ForTick {
YA5g';$H* [font="Times]public static void main(String args[]) {
[a<SDMR [font="Times]int n;
_Bj":rzY [font="Times]for(n=10; n>0; n--)
ijU*|8n{> [font="Times]System.out.println("tick " + n);
\lNN Msd& [font="Times]}
M"To&?OI [font="Times]}
|e0`nn= 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。
/_ajaz% 还有啊,[font="Times]for循环的部分可以为空的
A+?`?pOm& [font="Times]class ForVar {
Uoix [font="Times]public static void main(String args[]) {
BfiD9ka-z [font="Times]int i;
~7Ux@Sx; [font="Times]boolean done = false;
yEQs:v6L~ [font="Times]i = 0;
/2VJX@h [font="Times]for( ; !done; ) {
GsM<2@? [font="Times]System.out.println("i is " + i);
ku
M$UYTTX [font="Times]if(i == 10) done = true;
0Wp|1)ljA [font="Times]i++;
mRK>U$v [font="Times]}
G .4X' [font="Times]}
]
@fk] ]R [font="Times]}
循环语句的例子下载 zp?`N; [font="Times] 2.分支语句[font="Times]
11;zNjD| [font="Times] if/else语句
J<lO=
+mg [font="Times]class IfElse {
oe~b}: [font="Times]public static void main(String args[]) {
f(7GX3? [font="Times]int month = 4; // April
~flV`wy$$1 [font="Times]String season;
+[g,B1jt [font="Times]if(month == 12 || month == 1 || month == 2)
sW8dPw
O [font="Times]season = "Winter";
"tpSg [font="Times]else if(month == 3 || month == 4 || month == 5)
UJ6v(:z< [font="Times]season = "Spring";
eb$#A _m [font="Times]else if(month == 6 || month == 7 || month == 8)
~WV"SaA)*U [font="Times]season = "Summer";
&PtJ$0%q [font="Times]else if(month == 9 || month == 10 || month == 11)
"@8li^ [font="Times]season = "Autumn";
IMONgFBS [font="Times]else
kB%JNMF{A [font="Times]season = "Bogus Month";
y1L,0 ] [font="Times]System.out.println("April is in the " + season + ".");
7"D.L-H [font="Times]}
)@bQu~Y [font="Times]}
C$)onk [font="Times]//这段程序输出[font="Times]:
"U"Z 3* [font="Times]//April is in the Spring.
x'R`.
!g3 [font="Times]// 注意[font="Times] “[font="Times]||”是或运算
\Y}8S/] [font="Times] switch语句
mpJ#:}n [font="Times] class Switch {
D^;Uq8NDKq [font="Times]public static void main(String args[]) {
@"H>niG [font="Times]int month = 4;
"" ZQ/t\ [font="Times]String season;
Aq7osU1B [font="Times]switch (month) {
@7n"yp*" [font="Times]case 12:
0_t!T'jr7 [font="Times]case 1:
b>JDH1) [font="Times]case 2:
qJUK_6|3 [font="Times]season = "Winter";
y:l\$pGC% [font="Times]break;
{.mngRQF [font="Times]case 3:
$ L]lHji [font="Times]case 4:
~61v5@ [font="Times]case 5:
~W]TD@w [font="Times]season = "Spring";
+=8VTCn? [font="Times]break;
l1Fc>:o{ [font="Times]case 6:
M\Kx'N [font="Times]case 7:
m`r(p" [font="Times]case 8:
3=ymm^ [font="Times]season = "Summer";
hY8reQp1 [font="Times]break;
VyGJ=[ ] [font="Times]case 9:
N ZSSg2TX# [font="Times]case 10:
UFuX@Lu0 [font="Times]case 11:
$iz|\m [font="Times]season = "Autumn";
4+ Z]3oIRE [font="Times]break;
5/Uy{Xt [font="Times]default:
0{ R=9wcc [font="Times]season = "Bogus Month";
'2^Q1{ :\ [font="Times]}
6)Lk-D [font="Times]System.out.println("April is in the " + season + ".");
:9 ^*
^T [font="Times]}
kMd.h[X~ [font="Times]}
分支语句代码下载 Q]>.b%s[ 1&Z