全新java初学者实践教程6(Java SE5.0版)
>"=DN5w
,S 基本语法3
8TAJ#Lm <B0f Xj{fM\,"9 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:
R{bG`C8.d \5! 7zPc [font="Times] 1.循环语句[font="Times]:while,do-while,for
NZ i3U g<;::'6 [font="Times]2.分支语句[font="Times]:if-else,switch,
,e9M%VIu6[ [font="Times]
IaSpF<&Y; 3.跳转语句[font="Times] break,continue,label: 和[font="Times]return
2'- "&d+O [font="Times]
MYjc6@=cR 4.异常处理语句[font="Times]:try-catch-finally,throw
ojlyW})$% *-5N0K<kQ 实践:
4P1}XYD-2 [font="Times] 1.循环语句
KgkRs?'z [font="Times] while 语句
N2'aC}
I [font="Times]class While {
j:'g*IxM_ [font="Times]public static void main(String args[]) {
YK6'/2! [font="Times]int n = 10;
$qYP|W [font="Times]while(n > 0) {
F{a;=h#@Q [font="Times]System.out.println("tick " + n);
t>?tWSNf [font="Times]n--;
*n EkbI/ [font="Times]}
x,U_x [font="Times]}
E}S%yD[ [font="Times]}
51y"#\7 [font="Times] do…while 语句
<nqv)g"u0 [font="Times] class DoWhile {
h
':ZF [font="Times]public static void main(String args[]) {
lTq"j?#E]m [font="Times]int n = 10;
e*lL. [font="Times]do {
7CuZ7!>$ [font="Times]System.out.println("tick " + n);
ZGR5"el! [font="Times]n--;
f4Y)GO<R] [font="Times]} while(n > 0);
HW~-GcU-o [font="Times]}
V+lF|CZb5 [font="Times]}
xIa7F$R 0 二者区别,[font="Times]do…while至少循环一次,而[font="Times]while的表达式要是为[font="Times]flase的话可以一次也不循环。再通俗一点,[font="Times]do…while就算是括号里的是[font="Times]flase,人家最少也能[font="Times]do一次。
D 6y,Q [font="Times] for语句
jci,]*X4 [font="Times] class ForTick {
0] [font="Times]public static void main(String args[]) {
oS..y($TI [font="Times]int n;
io+V4m
[font="Times]for(n=10; n>0; n--)
1]~w?)..' [font="Times]System.out.println("tick " + n);
+Z|3[#W [font="Times]}
n8F5z|/ [font="Times]}
@
G)yz!H 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。
;H~<.QW 还有啊,[font="Times]for循环的部分可以为空的
NvJ5[W [font="Times]class ForVar {
~o%igJ
}.C [font="Times]public static void main(String args[]) {
xH*X5? [font="Times]int i;
HVHv,:bPo [font="Times]boolean done = false;
|0=UZK7%O [font="Times]i = 0;
+K'Hr:( [font="Times]for( ; !done; ) {
sNo8o1Hby [font="Times]System.out.println("i is " + i);
i}DS+~8v [font="Times]if(i == 10) done = true;
[A,^F0:h [font="Times]i++;
@pYEzizP7 [font="Times]}
iI IXv [font="Times]}
LO{Axf% [font="Times]}
循环语句的例子下载 PZusYeV8b [font="Times] 2.分支语句[font="Times]
*l+Dbm,u [font="Times] if/else语句
+ tMf&BZ [font="Times]class IfElse {
[MFnS",7c [font="Times]public static void main(String args[]) {
s||" } l [font="Times]int month = 4; // April
,u2Qkw [font="Times]String season;
PY^#hC5: [font="Times]if(month == 12 || month == 1 || month == 2)
qtZ?
kJ [font="Times]season = "Winter";
PT6]qS'1 [font="Times]else if(month == 3 || month == 4 || month == 5)
{k)gDJU [font="Times]season = "Spring";
|sReHt2)d [font="Times]else if(month == 6 || month == 7 || month == 8)
;cI*"-I:F [font="Times]season = "Summer";
Y!CUUWM [font="Times]else if(month == 9 || month == 10 || month == 11)
DHWz, M [font="Times]season = "Autumn";
Fa )QDBz) [font="Times]else
*$<W"@%^J [font="Times]season = "Bogus Month";
R^*baiXVI [font="Times]System.out.println("April is in the " + season + ".");
}LT&BNZj [font="Times]}
dg24h7|] [font="Times]}
>SK:b/i [font="Times]//这段程序输出[font="Times]:
(6S'wb [font="Times]//April is in the Spring.
L\PmT [font="Times]// 注意[font="Times] “[font="Times]||”是或运算
z~ C8JY: [font="Times] switch语句
s;Gd`-S>d [font="Times] class Switch {
"ntP92 8 [font="Times]public static void main(String args[]) {
$mn0I69 [font="Times]int month = 4;
D=#RQ- [font="Times]String season;
",$_\l [font="Times]switch (month) {
f_jhQ..g<g [font="Times]case 12:
AzOs/q8O [font="Times]case 1:
;2<5^hgk [font="Times]case 2:
{?H5Pw>{%h [font="Times]season = "Winter";
;KlYiu [font="Times]break;
hWT
jN [font="Times]case 3:
w*ans}P7 [font="Times]case 4:
wfmM`4Y [font="Times]case 5:
Cf2WBX$ [font="Times]season = "Spring";
\EySKQ= [font="Times]break;
C1k< P [font="Times]case 6:
=:^aBN# [font="Times]case 7:
L"m^LyU [font="Times]case 8:
n:%4SZn [font="Times]season = "Summer";
p%3z*2,( [font="Times]break;
GXtK3YAr [font="Times]case 9:
$8=|<vt [font="Times]case 10:
cKt=? [font="Times]case 11:
%y6(+I#P [font="Times]season = "Autumn";
N,Eap KG [font="Times]break;
hO=L|BJ?I [font="Times]default:
. 5(YL8d [font="Times]season = "Bogus Month";
K& #il [font="Times]}
I,{YxY[$7 [font="Times]System.out.println("April is in the " + season + ".");
SO$Af!S:bB [font="Times]}
!bE-&c [font="Times]}
分支语句代码下载 6Wu*zY_+ .:$(o& [font="Times]switch语句适合于条件非常多的逻辑
8W\yM;' 请看上述语句可以混合使用,请看
下载例子