全新java初学者实践教程6(Java SE5.0版)
!gD 3CA 基本语法3
7I @9v=xV Fh*q]1F XhJ P87A 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:
]1YYrgi7 gOBj0P8s|} [font="Times] 1.循环语句[font="Times]:while,do-while,for
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ku.@5 [font="Times]2.分支语句[font="Times]:if-else,switch,
J)#59a [font="Times]
hX{g]KE> 3.跳转语句[font="Times] break,continue,label: 和[font="Times]return
+?4*,8Tmmz [font="Times]
+ZD[[+ 4.异常处理语句[font="Times]:try-catch-finally,throw
Eg287B + MOe{:/6 实践:
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Ay> [font="Times] 1.循环语句
4\ uZKv@, [font="Times] while 语句
<lg"M;&Ht [font="Times]class While {
luP'JUq [font="Times]public static void main(String args[]) {
{9m!UlTtw [font="Times]int n = 10;
~@)-qV^~ [font="Times]while(n > 0) {
Vz=j)[ [font="Times]System.out.println("tick " + n);
n $D}0wSM/ [font="Times]n--;
Bd N{[2 [font="Times]}
sWojQ-8} [font="Times]}
7cOg(6N [font="Times]}
^`hI00u( [font="Times] do…while 语句
OuYE-x2]x" [font="Times] class DoWhile {
%WJ\'@O\ [font="Times]public static void main(String args[]) {
-.+KCt G$+ [font="Times]int n = 10;
Y]`lEq% [font="Times]do {
h&:Q$*A> [font="Times]System.out.println("tick " + n);
2V=FWuXC" [font="Times]n--;
TnMVHO- [font="Times]} while(n > 0);
>8F{lbEe [font="Times]}
E9 80yXJR [font="Times]}
7DC0 W|Fe 二者区别,[font="Times]do…while至少循环一次,而[font="Times]while的表达式要是为[font="Times]flase的话可以一次也不循环。再通俗一点,[font="Times]do…while就算是括号里的是[font="Times]flase,人家最少也能[font="Times]do一次。
2>_brz|7:| [font="Times] for语句
IlC:dA [font="Times] class ForTick {
32)&; [font="Times]public static void main(String args[]) {
\$$b",2
h [font="Times]int n;
F$sF
'cw [font="Times]for(n=10; n>0; n--)
Le#E! sU [font="Times]System.out.println("tick " + n);
vV&AG1_Mv [font="Times]}
h[[/p {z [font="Times]}
h~=\/vF 与上面那两个的区别,[font="Times]for循环执行的次数是可以在执行之前确定的。通俗一点说吧,看这个例子[font="Times] for(n=10; n>0; n--)就是在括号里的时候,就已经知道要循环[font="Times]10次了。
jl 30\M7 还有啊,[font="Times]for循环的部分可以为空的
sJjl)Qs)T [font="Times]class ForVar {
ECE{xoc [font="Times]public static void main(String args[]) {
mPw56> [font="Times]int i;
6qHvq
A, [font="Times]boolean done = false;
"0!eb3n [font="Times]i = 0;
|({UV-` [font="Times]for( ; !done; ) {
b;~EJ [font="Times]System.out.println("i is " + i);
sg9x?Bx9 [font="Times]if(i == 10) done = true;
21)-:rS [font="Times]i++;
^8f|clw" [font="Times]}
edImrm1f [font="Times]}
99+/W*C [font="Times]}
循环语句的例子下载 R;Gl{ [font="Times] 2.分支语句[font="Times]
X-;Qorb^ [font="Times] if/else语句
|=h)efo} [font="Times]class IfElse {
oE|u;o [font="Times]public static void main(String args[]) {
X{9JSq [font="Times]int month = 4; // April
4E>/*F! [font="Times]String season;
C^8)IN=$ [font="Times]if(month == 12 || month == 1 || month == 2)
U d=gdsL [font="Times]season = "Winter";
3 DO$^JJ. [font="Times]else if(month == 3 || month == 4 || month == 5)
1>*UbV<R;u [font="Times]season = "Spring";
0[$Mo3c+' [font="Times]else if(month == 6 || month == 7 || month == 8)
rz%[o,s [font="Times]season = "Summer";
A aF5` [font="Times]else if(month == 9 || month == 10 || month == 11)
kgbr+Yw2X [font="Times]season = "Autumn";
>1)@n3. <O [font="Times]else
1X!f!0=g+ [font="Times]season = "Bogus Month";
y uK5 r [font="Times]System.out.println("April is in the " + season + ".");
w Ycz\uV [font="Times]}
+y{93nl [font="Times]}
3Av(|<cR [font="Times]//这段程序输出[font="Times]:
2*7s9g [font="Times]//April is in the Spring.
:.'T+LI [font="Times]// 注意[font="Times] “[font="Times]||”是或运算
t$PnQ@xu [font="Times] switch语句
#K,qF* [font="Times] class Switch {
pb2{J# [font="Times]public static void main(String args[]) {
z"P,=M6De [font="Times]int month = 4;
uX5--o=C [font="Times]String season;
PE6u8ZAb" [font="Times]switch (month) {
a*n%SUP [font="Times]case 12:
:x*|lz[ [font="Times]case 1:
]rX?n [font="Times]case 2:
}9+1<mT9a/ [font="Times]season = "Winter";
dnWt\>6&
2 [font="Times]break;
3{#pd6e5 [font="Times]case 3:
g$^qQs)^N [font="Times]case 4:
$X<<JnsK [font="Times]case 5:
uB#B\i [font="Times]season = "Spring";
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