全新java初学者实践教程6(Java SE5.0版)
}f<.07 基本语法3
%.BbPR 7?h GrW+P[j9 .#6Dad=S* 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:
<u*~RYA2 'd^U!l [font="Times] 1.循环语句[font="Times]:while,do-while,for
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[font="Times]2.分支语句[font="Times]:if-else,switch,
%7Z_Hw [font="Times]
y|nMCkuX 3.跳转语句[font="Times] break,continue,label: 和[font="Times]return
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[font="Times]
,+KZn}> 4.异常处理语句[font="Times]:try-catch-finally,throw
s$:F^sxb pRD8/7@(B{ 实践:
"CB* [font="Times] 1.循环语句
@/ wJW``; [font="Times] while 语句
T c4N\Cy [font="Times]class While {
h2zuPgz, [font="Times]public static void main(String args[]) {
,g#=pdX; [font="Times]int n = 10;
1 +O- g [font="Times]while(n > 0) {
l];,)ddD9 [font="Times]System.out.println("tick " + n);
D!ToCVos [font="Times]n--;
p V(b>O [font="Times]}
C+cSy'VIK! [font="Times]}
@U_w:Q<9u [font="Times]}
kV(}45i]s [font="Times] do…while 语句
9l@VxX68M [font="Times] class DoWhile {
`)&-;CMY [font="Times]public static void main(String args[]) {
ddmTMfH [font="Times]int n = 10;
z"u4t.KpL [font="Times]do {
mZDrvTI' [font="Times]System.out.println("tick " + n);
[7ZFxr\:! [font="Times]n--;
9;k_"@A6 [font="Times]} while(n > 0);
*
'WzIk2 [font="Times]}
!1]72%k[ [font="Times]}
p}hOkx4R\ 二者区别,[font="Times]do…while至少循环一次,而[font="Times]while的表达式要是为[font="Times]flase的话可以一次也不循环。再通俗一点,[font="Times]do…while就算是括号里的是[font="Times]flase,人家最少也能[font="Times]do一次。
@>_`g= [font="Times] for语句
`$jc=ZLm [font="Times] class ForTick {
aIpDf|~ [font="Times]public static void main(String args[]) {
G)';ucs:, [font="Times]int n;
p\wE})mu [font="Times]for(n=10; n>0; n--)
)dbi [font="Times]System.out.println("tick " + n);
DmM<Kkg.J [font="Times]}
ns9iTU) [font="Times]}
ce\]o^4 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。
fmXA;^% 还有啊,[font="Times]for循环的部分可以为空的
_|bIl%W;\' [font="Times]class ForVar {
CDQ}C=4 [font="Times]public static void main(String args[]) {
SEq_37 [font="Times]int i;
+u#;k!B/> [font="Times]boolean done = false;
k)UF.=$d [font="Times]i = 0;
UJ1iXV[h" [font="Times]for( ; !done; ) {
5m!FtHvm1 [font="Times]System.out.println("i is " + i);
!5wm9I!5^ [font="Times]if(i == 10) done = true;
dq28Y$9~ [font="Times]i++;
$J>GCY [font="Times]}
Fd":\7p [font="Times]}
.$y}}/{j?[ [font="Times]}
循环语句的例子下载 qv y~b [font="Times] 2.分支语句[font="Times]
MU4/arXy [font="Times] if/else语句
$NC1>83 [font="Times]class IfElse {
L!Iu\_{q [font="Times]public static void main(String args[]) {
<UOx >=h [font="Times]int month = 4; // April
CvKXVhf0$J [font="Times]String season;
l69&-Nyg [font="Times]if(month == 12 || month == 1 || month == 2)
SCs@Q [font="Times]season = "Winter";
Gkv<)}G [font="Times]else if(month == 3 || month == 4 || month == 5)
>j5)
MF{" [font="Times]season = "Spring";
x*Y&s< [font="Times]else if(month == 6 || month == 7 || month == 8)
_]a8lr+_- [font="Times]season = "Summer";
"Kx2k>ym [font="Times]else if(month == 9 || month == 10 || month == 11)
YQ9@Dk0R
[font="Times]season = "Autumn";
N=^{FZ [font="Times]else
mD{<Lp= [font="Times]season = "Bogus Month";
`,gGmh [font="Times]System.out.println("April is in the " + season + ".");
~s{yh-B [font="Times]}
wYQTG*&h [font="Times]}
i_Dv+^&zV [font="Times]//这段程序输出[font="Times]:
? piv]Z [font="Times]//April is in the Spring.
y|f`sBMM [font="Times]// 注意[font="Times] “[font="Times]||”是或运算
~G|un}g= [font="Times] switch语句
>Ig%|4Hw [font="Times] class Switch {
++d(}^C; [font="Times]public static void main(String args[]) {
W iql c [font="Times]int month = 4;
.VG$`g" [font="Times]String season;
Oa~|a7 `o [font="Times]switch (month) {
f_a.BTtNO [font="Times]case 12:
k>y68_ [font="Times]case 1:
Pw
i6Ly` [font="Times]case 2:
NSH20$A< [font="Times]season = "Winter";
WBD e` [font="Times]break;
W`_pjld [font="Times]case 3:
vH/z|< [font="Times]case 4:
:9un6A9JS [font="Times]case 5:
Y[Jt+p] [font="Times]season = "Spring";
}#}IR5`=E [font="Times]break;
0vOt.LC/S [font="Times]case 6:
- 6a4H?L [font="Times]case 7:
b*Ny [font="Times]case 8:
$0>>Z [font="Times]season = "Summer";
,_;+H*H>" [font="Times]break;
l^aG"")TH. [font="Times]case 9:
RzCC>- [font="Times]case 10:
S-V)!6\cK [font="Times]case 11:
3Z=OUhn9 [font="Times]season = "Autumn";
[SGt ~bRJ [font="Times]break;
Ylbh_ d~BU [font="Times]default:
RU&,z3LEb [font="Times]season = "Bogus Month";
Gh}k9-L [font="Times]}
,0+%ji^V [font="Times]System.out.println("April is in the " + season + ".");
~wG.'d] [font="Times]}
M,xhQ{eBY [font="Times]}
分支语句代码下载 QWVH4rg ;d$PQi [font="Times]switch语句适合于条件非常多的逻辑
*fyC@fI> 请看上述语句可以混合使用,请看
下载例子