全新java初学者实践教程6(Java SE5.0版)
Uax+dl 基本语法3
|AZg*T3:W yA{W /iG*)6*^k 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:
Pxn,Qw* P"sA [font="Times] 1.循环语句[font="Times]:while,do-while,for
p=/m XdH\OJ [font="Times]2.分支语句[font="Times]:if-else,switch,
at2FmBdu C [font="Times]
UR:aD_h 3.跳转语句[font="Times] break,continue,label: 和[font="Times]return
m*e{\)rd# [font="Times]
zy*/T>{# 4.异常处理语句[font="Times]:try-catch-finally,throw
0$r^C6}f FP[!BUOf" 实践:
B^).BQ [font="Times] 1.循环语句
aq7~QX_0G [font="Times] while 语句
"3FihE]k [font="Times]class While {
5s(1[( [font="Times]public static void main(String args[]) {
5SCKP<rb [font="Times]int n = 10;
04r$>#E [font="Times]while(n > 0) {
L(GjZAP [font="Times]System.out.println("tick " + n);
j*xV!DqC [font="Times]n--;
`y#UJYXQE [font="Times]}
vb9OonE2 [font="Times]}
E2)h?cs [font="Times]}
54zlnM$ [font="Times] do…while 语句
);-~j [font="Times] class DoWhile {
Z{'i F [font="Times]public static void main(String args[]) {
tTd\| [font="Times]int n = 10;
1;<R#>&,* [font="Times]do {
x@8a'' [font="Times]System.out.println("tick " + n);
KZ~*Nz+H2 [font="Times]n--;
R$zH] [font="Times]} while(n > 0);
6q
2_WX [font="Times]}
q -8t'7 [font="Times]}
3Hf0MAt 二者区别,[font="Times]do…while至少循环一次,而[font="Times]while的表达式要是为[font="Times]flase的话可以一次也不循环。再通俗一点,[font="Times]do…while就算是括号里的是[font="Times]flase,人家最少也能[font="Times]do一次。
+iOKb c' [font="Times] for语句
D7_*k%;@ [font="Times] class ForTick {
VK@!lJu! [font="Times]public static void main(String args[]) {
Q1@A2+ c [font="Times]int n;
0527Wj [font="Times]for(n=10; n>0; n--)
|Ph3#^rM? [font="Times]System.out.println("tick " + n);
"`N-* ;*W [font="Times]}
\W,I?Kx$ [font="Times]}
KZPEG!-5 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。
B=|cS;bM$3 还有啊,[font="Times]for循环的部分可以为空的
X$/2[o#g [font="Times]class ForVar {
I-OJVZ( V [font="Times]public static void main(String args[]) {
a22XDes= [font="Times]int i;
q+,Q<2J [font="Times]boolean done = false;
Jmx Ko+- [font="Times]i = 0;
ws4cF
N9P? [font="Times]for( ; !done; ) {
f 2l{^E#h [font="Times]System.out.println("i is " + i);
G@j0rnn>B [font="Times]if(i == 10) done = true;
nS>8bub30 [font="Times]i++;
[$[:"N_ [font="Times]}
*hcYGLx
r [font="Times]}
+>JjvYx}\ [font="Times]}
循环语句的例子下载 m.,U:> [font="Times] 2.分支语句[font="Times]
I!^O)4QRx [font="Times] if/else语句
fFQ|T:vm [font="Times]class IfElse {
p,"g+ MwP [font="Times]public static void main(String args[]) {
6AocmR0D' [font="Times]int month = 4; // April
EYA,hc [font="Times]String season;
=*Bl|;>6 [font="Times]if(month == 12 || month == 1 || month == 2)
/*0K92NB [font="Times]season = "Winter";
7`u$ [font="Times]else if(month == 3 || month == 4 || month == 5)
y(
y8+ZT [font="Times]season = "Spring";
B#9{-t3Vf [font="Times]else if(month == 6 || month == 7 || month == 8)
@IXsy [font="Times]season = "Summer";
(W}bG>!#Q8 [font="Times]else if(month == 9 || month == 10 || month == 11)
>rvQw63\ [font="Times]season = "Autumn";
CirZ+o [font="Times]else
jlxpt)0i [font="Times]season = "Bogus Month";
2#k5+?-c61 [font="Times]System.out.println("April is in the " + season + ".");
AlJ} >u [font="Times]}
*?MGMhE [font="Times]}
fDLG>rXPT [font="Times]//这段程序输出[font="Times]:
=FD;~ [font="Times]//April is in the Spring.
B5$kHM%p [font="Times]// 注意[font="Times] “[font="Times]||”是或运算
itMg|%B% [font="Times] switch语句
D_Bb?o5 [font="Times] class Switch {
"jw<V,, [font="Times]public static void main(String args[]) {
T1H"\+ [font="Times]int month = 4;
OrK&RC [font="Times]String season;
P9 Z}H(?C [font="Times]switch (month) {
)2M>3C6>f [font="Times]case 12:
~y7jCcd` [font="Times]case 1:
=9T$Gr [font="Times]case 2:
64
5z#_}C$ [font="Times]season = "Winter";
8U_{|]M
[font="Times]break;
J[&b`A@.o [font="Times]case 3:
M9f35
: [font="Times]case 4:
]kboG%Dl?9 [font="Times]case 5:
RD.V'`n" [font="Times]season = "Spring";
I|Gp$uq _ [font="Times]break;
l}qE 46EL [font="Times]case 6:
^b
%0B [font="Times]case 7:
/7
Cn(s5 o [font="Times]case 8:
7VP32Eh[ [font="Times]season = "Summer";
`/_G$_ [font="Times]break;
4ni3kmvX [font="Times]case 9:
A%^ILyU6c [font="Times]case 10:
0x!2ihf [font="Times]case 11:
Fgh]KQ/5 [font="Times]season = "Autumn";
QPq7R [font="Times]break;
KZeQ47| [font="Times]default:
0Zg%+)iy@ [font="Times]season = "Bogus Month";
'}9JCJ [font="Times]}
Lco&Fp [font="Times]System.out.println("April is in the " + season + ".");
{%C7EAq* [font="Times]}
\J6j38D5 [font="Times]}
分支语句代码下载 SV(]9^nW 'PP#^aI, [font="Times]switch语句适合于条件非常多的逻辑
(IPY^>h 请看上述语句可以混合使用,请看
下载例子