全新java初学者实践教程6(Java SE5.0版)
~~{+?v6B] 基本语法3
?d@zTAI ""x>-j4 Frum@n 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:
@P6*4W RpU.v
` [font="Times] 1.循环语句[font="Times]:while,do-while,for
]I(<hDuRp aU%QJ#j [font="Times]2.分支语句[font="Times]:if-else,switch,
,`ju(ac! [font="Times]
qw}.
QwPT 3.跳转语句[font="Times] break,continue,label: 和[font="Times]return
!]=S A & [font="Times]
ONm-zRx| 4.异常处理语句[font="Times]:try-catch-finally,throw
[*^rH: ]3CWb>!_ 实践:
rz.`$ [font="Times] 1.循环语句
;!pJ%p0Sc [font="Times] while 语句
~o8x3`CoF [font="Times]class While {
3(=QY) [font="Times]public static void main(String args[]) {
jDCf]NvOPM [font="Times]int n = 10;
$B?IE#7S4 [font="Times]while(n > 0) {
`WlQ<QEi [font="Times]System.out.println("tick " + n);
]DLs'W;) [font="Times]n--;
h[r)HX0hA [font="Times]}
:djbZ>< [font="Times]}
:;N2hnHoG [font="Times]}
V7$-4%NL [font="Times] do…while 语句
c!J|vRA5 [font="Times] class DoWhile {
->5[C0: ] [font="Times]public static void main(String args[]) {
f- ~] [font="Times]int n = 10;
k5eTfaxl [font="Times]do {
-5<G^AS [font="Times]System.out.println("tick " + n);
?T_bjALW [font="Times]n--;
}Ih5`$ [font="Times]} while(n > 0);
RwDXOdgu [font="Times]}
MsjC4(Xla. [font="Times]}
YAYwrKt 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。
c->?'h23) [font="Times] for语句
M`QK{$1p [font="Times] class ForTick {
?xb2jZ/0X [font="Times]public static void main(String args[]) {
tW"s^r=95 [font="Times]int n;
@+;
cFj [font="Times]for(n=10; n>0; n--)
x(y=.4Yf+ [font="Times]System.out.println("tick " + n);
TZw['o [font="Times]}
7!^Zsp^+ [font="Times]}
KBwY _ 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。
#s|,oIm 还有啊,[font="Times]for循环的部分可以为空的
lcuqzX{7 [font="Times]class ForVar {
`k~w
14~w [font="Times]public static void main(String args[]) {
?/^{sW'
| [font="Times]int i;
z i3gE$7 [font="Times]boolean done = false;
Jp +h''t [font="Times]i = 0;
Ql?>,FZ [font="Times]for( ; !done; ) {
9 N9Q#o$!. [font="Times]System.out.println("i is " + i);
F{F SmUxzK [font="Times]if(i == 10) done = true;
Rj~y#m [font="Times]i++;
jP"yG# [font="Times]}
Zl{DqC^ [font="Times]}
t[X,m]SX [font="Times]}
循环语句的例子下载 Sbjc8V ut [font="Times] 2.分支语句[font="Times]
PAs.T4Av^ [font="Times] if/else语句
R6qC0@* [font="Times]class IfElse {
Ls{]ohP [font="Times]public static void main(String args[]) {
y.?Q [font="Times]int month = 4; // April
ANXN.V [font="Times]String season;
2>Sr04Pt [font="Times]if(month == 12 || month == 1 || month == 2)
!=(M P: [font="Times]season = "Winter";
.
/~# [font="Times]else if(month == 3 || month == 4 || month == 5)
qaEWK0 [font="Times]season = "Spring";
)/uCdSDIc [font="Times]else if(month == 6 || month == 7 || month == 8)
{z7kW@c [font="Times]season = "Summer";
a'B 5m]% [font="Times]else if(month == 9 || month == 10 || month == 11)
./Wi(p{F [font="Times]season = "Autumn";
?oQAxb& [font="Times]else
[OQ+&\ [font="Times]season = "Bogus Month";
mM-7
jz [font="Times]System.out.println("April is in the " + season + ".");
R1C2d +L [font="Times]}
Zksow} % [font="Times]}
I8LoXY [font="Times]//这段程序输出[font="Times]:
A:,R.P>`C [font="Times]//April is in the Spring.
*sq+ Vc( [font="Times]// 注意[font="Times] “[font="Times]||”是或运算
77~l~EX [font="Times] switch语句
K]yUPx [font="Times] class Switch {
`d!~)D [font="Times]public static void main(String args[]) {
+*KDtqZjk [font="Times]int month = 4;
x*0mmlCb [font="Times]String season;
BnIZ+fg= [font="Times]switch (month) {
0j2M< W# [font="Times]case 12:
lv\^@9r [font="Times]case 1:
]M/*Beh [font="Times]case 2:
6|ENDd[ [font="Times]season = "Winter";
l&6+ykQ [font="Times]break;
tk'3Q 1L [font="Times]case 3:
}d 16xp [font="Times]case 4:
0A.9<&Lod [font="Times]case 5:
o3>D~9 [font="Times]season = "Spring";
E?F?)!% [font="Times]break;
6cbIs_g [font="Times]case 6:
-mqTlXM [font="Times]case 7:
CB>O%m[1 [font="Times]case 8:
7A46?kfu [font="Times]season = "Summer";
J)_IfbY [font="Times]break;
99&PY[f:{ [font="Times]case 9:
WkK.ON^ [font="Times]case 10:
1iIag}?p [font="Times]case 11:
i0*6o3h [font="Times]season = "Autumn";
Nzel^~ [font="Times]break;
FHbw& [font="Times]default:
If%**o [font="Times]season = "Bogus Month";
1}b1RKKj< [font="Times]}
]|)M /U * [font="Times]System.out.println("April is in the " + season + ".");
BZ>,Qh!J [font="Times]}
{ZD'l5jU [font="Times]}
分支语句代码下载 iM{UB=C ~OOD#/ [font="Times]switch语句适合于条件非常多的逻辑
v#Y9O6g]T 请看上述语句可以混合使用,请看
下载例子