全新java初学者实践教程6(Java SE5.0版)
ns[Q %_ 基本语法3
n*fsdo~ j*)K>
\ 0E#3XhU 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:
v/lQ5R1 @#5PPXp [font="Times] 1.循环语句[font="Times]:while,do-while,for
g{06d~Y VjVL/SO/ [font="Times]2.分支语句[font="Times]:if-else,switch,
WKPuIE: [font="Times]
<oWoJP`G 3.跳转语句[font="Times] break,continue,label: 和[font="Times]return
{]\!vG6 [font="Times]
m2$Qp{C6H 4.异常处理语句[font="Times]:try-catch-finally,throw
YV0K&d L>EC^2\ 实践:
S7
Tem:/ [font="Times] 1.循环语句
?]L:j [font="Times] while 语句
!EQMTF=( [font="Times]class While {
^yB>0/{)z [font="Times]public static void main(String args[]) {
SNK
_ [font="Times]int n = 10;
O.8{c; [font="Times]while(n > 0) {
kdrya [font="Times]System.out.println("tick " + n);
"Aq-H g [font="Times]n--;
GM<r{6Qy [font="Times]}
R\wG3Oxol [font="Times]}
G}b LWA [font="Times]}
[!E8 C9Q#! [font="Times] do…while 语句
bJE$> [font="Times] class DoWhile {
Wg+fT{[f| [font="Times]public static void main(String args[]) {
sy|{}NkA! [font="Times]int n = 10;
jreY'y: [font="Times]do {
L>mv\D;o. [font="Times]System.out.println("tick " + n);
`)W}4itm
[font="Times]n--;
LAwl9YnG: [font="Times]} while(n > 0);
8HyK;+ZkVd [font="Times]}
g2<xr;<t^ [font="Times]}
wb
}W;C@ 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。
m_z1|zM}o [font="Times] for语句
_YH)E^If [font="Times] class ForTick {
Rz!E=1Y$ [font="Times]public static void main(String args[]) {
v*nX [font="Times]int n;
\5%T'S@5 [font="Times]for(n=10; n>0; n--)
g[P8 [font="Times]System.out.println("tick " + n);
c!BiGw,; [font="Times]}
Pxj?W'| [font="Times]}
:B<lDcFKJ 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。
K6.*)7$# 还有啊,[font="Times]for循环的部分可以为空的
7
C5m#e3 [font="Times]class ForVar {
K/y#hP [font="Times]public static void main(String args[]) {
oh5fNx [font="Times]int i;
q
lL6wzq, [font="Times]boolean done = false;
uL!{xuN [font="Times]i = 0;
shlL(&Py [font="Times]for( ; !done; ) {
,OLN%2Sq [font="Times]System.out.println("i is " + i);
PT|W{RlNl [font="Times]if(i == 10) done = true;
pt;kN&A^ [font="Times]i++;
wL2d.$?TEg [font="Times]}
X}yEMe{T [font="Times]}
~mtL\!vaM [font="Times]}
循环语句的例子下载 rBP!RSl1 [font="Times] 2.分支语句[font="Times]
R4"g?
e [font="Times] if/else语句
eD* "#O)W [font="Times]class IfElse {
(d[)U< [font="Times]public static void main(String args[]) {
%cD7}o:u [font="Times]int month = 4; // April
@>J4K#" [font="Times]String season;
"YGs<)S [font="Times]if(month == 12 || month == 1 || month == 2)
m&OzT~?_>N [font="Times]season = "Winter";
@fp(uu [font="Times]else if(month == 3 || month == 4 || month == 5)
EM*YN=S o [font="Times]season = "Spring";
'Z-jj2t} [font="Times]else if(month == 6 || month == 7 || month == 8)
()vxTTa [font="Times]season = "Summer";
f4zd(J [font="Times]else if(month == 9 || month == 10 || month == 11)
74%,v| [font="Times]season = "Autumn";
+EcN[-~ [font="Times]else
S5'BXE, [font="Times]season = "Bogus Month";
9[|Ql [font="Times]System.out.println("April is in the " + season + ".");
[t
/hjm"$ [font="Times]}
lhx6+w [font="Times]}
m5sgcxt/ [font="Times]//这段程序输出[font="Times]:
a Kb2:1EQ [font="Times]//April is in the Spring.
&gkloP@ [font="Times]// 注意[font="Times] “[font="Times]||”是或运算
NrTQ}_3) [font="Times] switch语句
RaAi9b[/S [font="Times] class Switch {
gQ*0Mk [font="Times]public static void main(String args[]) {
pHY~_^B4& [font="Times]int month = 4;
8@qYzSx[ [font="Times]String season;
)5Kzq6. [font="Times]switch (month) {
. #;ZM[v [font="Times]case 12:
MZE8Cvq0 [font="Times]case 1:
koC2bX [font="Times]case 2:
5 %q26& [font="Times]season = "Winter";
(hVhzw"~ [font="Times]break;
G;FY2;adK [font="Times]case 3:
V$-IRdb [font="Times]case 4:
(eN\s98)/ [font="Times]case 5:
:M1S*"&: [font="Times]season = "Spring";
5>q|c`&}E [font="Times]break;
.-[UHO05^8 [font="Times]case 6:
;]MHU/ [font="Times]case 7:
\A _g [font="Times]case 8:
,~gY'Ql [font="Times]season = "Summer";
`R fhxzI [font="Times]break;
NZ'S~Lr [font="Times]case 9:
j|KZ HH%dc [font="Times]case 10:
eM+]KG)} [font="Times]case 11:
zMKW@ [font="Times]season = "Autumn";
(D{Fln\ [font="Times]break;
h{yqNl [font="Times]default:
v-X1if1% [font="Times]season = "Bogus Month";
BM1uZJ0 [font="Times]}
~DVAk|fc [font="Times]System.out.println("April is in the " + season + ".");
&2MW.,e7s [font="Times]}
>.SU=HG; [font="Times]}
分支语句代码下载 <Jo_f&&{ Io{)@H"f [font="Times]switch语句适合于条件非常多的逻辑
+o!".Hp 请看上述语句可以混合使用,请看
下载例子