全新java初学者实践教程6(Java SE5.0版)
m[C-/f^u| 基本语法3
M? oK@i EW{z?/ +xwz.::: 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:
p
IXBJk 5yO6szg [font="Times] 1.循环语句[font="Times]:while,do-while,for
j3rBEQ,R o)7gKWjujP [font="Times]2.分支语句[font="Times]:if-else,switch,
-tSWYp{ [font="Times]
(KHTgZ6 3.跳转语句[font="Times] break,continue,label: 和[font="Times]return
dvk?A$ [font="Times]
tqIz$84G 4.异常处理语句[font="Times]:try-catch-finally,throw
iZQwo3"8r ](vshgp2 实践:
Xz0jjO, [font="Times] 1.循环语句
0CxQ@~ttl [font="Times] while 语句
A?3hNvfx [font="Times]class While {
lkV%
k1w [font="Times]public static void main(String args[]) {
:Q sGwhB [font="Times]int n = 10;
gO?+:}! [font="Times]while(n > 0) {
/b20!3 [font="Times]System.out.println("tick " + n);
glh2CRUj [font="Times]n--;
"';'*x [font="Times]}
YZf<S: [font="Times]}
[SgP1>M [font="Times]}
r:y*l4 [font="Times] do…while 语句
jNV2o [font="Times] class DoWhile {
'z2}qJJ) [font="Times]public static void main(String args[]) {
UnZ*"% [font="Times]int n = 10;
}.7!@!q. [font="Times]do {
0%}$@H5i [font="Times]System.out.println("tick " + n);
PEoOs [font="Times]n--;
!J[3U
[font="Times]} while(n > 0);
cU5x8[2 [font="Times]}
~ @Ib:M [font="Times]}
J1Mm,LTO 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。
xmTa$tR+ [font="Times] for语句
N<:5 r [font="Times] class ForTick {
*J?QXsg [font="Times]public static void main(String args[]) {
d5]9FIj [font="Times]int n;
Y*O7lZuF% [font="Times]for(n=10; n>0; n--)
S)z
jfJR [font="Times]System.out.println("tick " + n);
BN@*CG [font="Times]}
[bJ/$A [font="Times]}
X4&{/;$ 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。
y yrCO"eh 还有啊,[font="Times]for循环的部分可以为空的
0^|)[2m! [font="Times]class ForVar {
}3Pz{{B&+O [font="Times]public static void main(String args[]) {
;'dw`)~jQ [font="Times]int i;
&Hc8u,| [font="Times]boolean done = false;
GdR>S(' [font="Times]i = 0;
9'Y~! vY [font="Times]for( ; !done; ) {
FqQm*k_ [font="Times]System.out.println("i is " + i);
/Yc!m$uCW [font="Times]if(i == 10) done = true;
'@wYr|s4 [font="Times]i++;
R,/?p [font="Times]}
()K%Rn [font="Times]}
X\hD4r"
[font="Times]}
循环语句的例子下载 )m"NO/sJ2 [font="Times] 2.分支语句[font="Times]
D*`|MzlQ [font="Times] if/else语句
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PU?k [font="Times]class IfElse {
1okL]VrI [font="Times]public static void main(String args[]) {
abWmPi [font="Times]int month = 4; // April
N6$pOQ [font="Times]String season;
oGly|L> [font="Times]if(month == 12 || month == 1 || month == 2)
,y3o ,gl [font="Times]season = "Winter";
57)S" [font="Times]else if(month == 3 || month == 4 || month == 5)
xg'z_W [font="Times]season = "Spring";
D<#+ R" [font="Times]else if(month == 6 || month == 7 || month == 8)
`.Y["f
1B [font="Times]season = "Summer";
Mvrc[s+o [font="Times]else if(month == 9 || month == 10 || month == 11)
F^IYx~: [font="Times]season = "Autumn";
C!B2.:ja [font="Times]else
-Uq I=# [font="Times]season = "Bogus Month";
,2[laJ [font="Times]System.out.println("April is in the " + season + ".");
5P
-IZ8~$ [font="Times]}
/lm;.7_J+ [font="Times]}
4/S4bk*8 [font="Times]//这段程序输出[font="Times]:
7h<Q{X<A [font="Times]//April is in the Spring.
LS Na [font="Times]// 注意[font="Times] “[font="Times]||”是或运算
%U)/>Z [font="Times] switch语句
$91c9z;f^ [font="Times] class Switch {
D.j'n-yw [font="Times]public static void main(String args[]) {
- P1OD)B [font="Times]int month = 4;
8Cs)_bj#! [font="Times]String season;
q0.+ F4 [font="Times]switch (month) {
^P~%^?( [font="Times]case 12:
U'UV=:/- [font="Times]case 1:
}/[tB [font="Times]case 2:
utQE$0F [font="Times]season = "Winter";
nE+sbfC [font="Times]break;
*pk*ijdB [font="Times]case 3:
r{$ip"f [font="Times]case 4:
bAeC=?U [font="Times]case 5:
yW^[{)V 3% [font="Times]season = "Spring";
#c'yAa [font="Times]break;
F5gL-\6 [font="Times]case 6:
?7@B$OlU [font="Times]case 7:
j =r`[Bm [font="Times]case 8:
o
<0 f [font="Times]season = "Summer";
8V;@yzIha [font="Times]break;
{tV)+T [font="Times]case 9:
%8>s :YG [font="Times]case 10:
OSQZ5:g| [font="Times]case 11:
z6ISJb [font="Times]season = "Autumn";
L6./b; [font="Times]break;
|iKk'Rta4 [font="Times]default:
(9%
ki$=}+ [font="Times]season = "Bogus Month";
bXF>{%(}E [font="Times]}
Oi AZA< [font="Times]System.out.println("April is in the " + season + ".");
(4cWq!ax<$ [font="Times]}
^q5~;_z| [font="Times]}
分支语句代码下载 3('=+d[}Vw px %xoY [font="Times]switch语句适合于条件非常多的逻辑
26PUO$&b. 请看上述语句可以混合使用,请看
下载例子