全新java初学者实践教程6(Java SE5.0版)
5CZii=@ 基本语法3
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) CA7 ZoMB# hr&&"d {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:
m}\G.$ h4 p2N;- [font="Times] 1.循环语句[font="Times]:while,do-while,for
D[2I_3[wp 6/ir("LK [font="Times]2.分支语句[font="Times]:if-else,switch,
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]iewukB4 3.跳转语句[font="Times] break,continue,label: 和[font="Times]return
isaDIl;L/ [font="Times]
NIcPjo 4.异常处理语句[font="Times]:try-catch-finally,throw
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.lVC>UT 实践:
jM8e2z3 [font="Times] 1.循环语句
lwEJ)Bv [font="Times] while 语句
99%oY [font="Times]class While {
} 5~|h% [font="Times]public static void main(String args[]) {
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4!|r [font="Times]int n = 10;
Fp>iwdjFg [font="Times]while(n > 0) {
h}&WBN [font="Times]System.out.println("tick " + n);
T8&
kxp [font="Times]n--;
$Hcp.J[O [font="Times]}
8W$uw~|dw [font="Times]}
ezRhSN? [font="Times]}
-1Acprr [font="Times] do…while 语句
3n;UXYJ% [font="Times] class DoWhile {
hj@< wU [font="Times]public static void main(String args[]) {
gs)wQgJ [ [font="Times]int n = 10;
Ek|#P{! [font="Times]do {
>p4#AfGF [font="Times]System.out.println("tick " + n);
M>+FIb( [font="Times]n--;
4LqJ4jo [font="Times]} while(n > 0);
?-CZJr [font="Times]}
{-*+G] [font="Times]}
(Zi(6 T\z 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。
SoZ$1$o2 [font="Times] for语句
Mg?^ 5`* [font="Times] class ForTick {
cn&\q.!fh [font="Times]public static void main(String args[]) {
">vxYi [font="Times]int n;
!+tz<9BBY [font="Times]for(n=10; n>0; n--)
m\>531& [font="Times]System.out.println("tick " + n);
U)~?/s{v [font="Times]}
w5 nzS)B:u [font="Times]}
MP/6AAt7=| 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。
T#'+w@Q9{9 还有啊,[font="Times]for循环的部分可以为空的
\I J\ [font="Times]class ForVar {
#9aB3C [font="Times]public static void main(String args[]) {
1&A@Zo5| [font="Times]int i;
aIV(&7KT4 [font="Times]boolean done = false;
07WZ w1(; [font="Times]i = 0;
a+!#cQl [font="Times]for( ; !done; ) {
LaL.C^K [font="Times]System.out.println("i is " + i);
w
'?xewx [font="Times]if(i == 10) done = true;
&z[39Q{~ [font="Times]i++;
NF`WA-W8@ [font="Times]}
?I{pv4G: [font="Times]}
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循环语句的例子下载 H^cB?i [font="Times] 2.分支语句[font="Times]
BX :77?9,+ [font="Times] if/else语句
aBk~/ [font="Times]class IfElse {
9 p6QNDp [font="Times]public static void main(String args[]) {
r|t;# [font="Times]int month = 4; // April
P@P(&{@ [font="Times]String season;
et|QW;*L [font="Times]if(month == 12 || month == 1 || month == 2)
Fy!uxT-\ [font="Times]season = "Winter";
#g,JNJ} [font="Times]else if(month == 3 || month == 4 || month == 5)
`6:;*#jO, [font="Times]season = "Spring";
FSZQ2*n5 [font="Times]else if(month == 6 || month == 7 || month == 8)
7Io]2)V [font="Times]season = "Summer";
+JoE[; [font="Times]else if(month == 9 || month == 10 || month == 11)
ZS51QB [font="Times]season = "Autumn";
"L^Klk?Vn [font="Times]else
Ipo?>To [font="Times]season = "Bogus Month";
yi`Z(j; [font="Times]System.out.println("April is in the " + season + ".");
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MNURY A= [font="Times]}
k,o|"9H [font="Times]//这段程序输出[font="Times]:
jEr/*kv [font="Times]//April is in the Spring.
e%#(:L [font="Times]// 注意[font="Times] “[font="Times]||”是或运算
6x%uWZa' [font="Times] switch语句
u4QPO:,a4 [font="Times] class Switch {
~e<l`rg# [font="Times]public static void main(String args[]) {
7kmU/(8 [font="Times]int month = 4;
kfaRN^ [font="Times]String season;
hhjT{>je [font="Times]switch (month) {
jUjgxP*7m [font="Times]case 12:
U
X)k;h [font="Times]case 1:
rZ<n0w [font="Times]case 2:
.>z)6S_G [font="Times]season = "Winter";
)-$Od2u2c [font="Times]break;
9-)D"ZhLe [font="Times]case 3:
]k~k6#),; [font="Times]case 4:
GtcY){7 [font="Times]case 5:
,4$ZB(\ [font="Times]season = "Spring";
9?c0cwP? [font="Times]break;
tRU+6D
<w [font="Times]case 6:
_[|~(lDJl [font="Times]case 7:
3=w$1.B d [font="Times]case 8:
vZj:\geV [font="Times]season = "Summer";
'PW~4f/m [font="Times]break;
(S/f!Dk&3 [font="Times]case 9:
,f0|eu> [font="Times]case 10:
j'Ry.8} [font="Times]case 11:
g.yr)
LHt0 [font="Times]season = "Autumn";
K3jKOV8 [font="Times]break;
] h3~>8< [font="Times]default:
,$irJz F [font="Times]season = "Bogus Month";
M\5aJ:cQ+ [font="Times]}
TJS/ O~= [font="Times]System.out.println("April is in the " + season + ".");
Zt:.+.dV [font="Times]}
K=x>%6W7b [font="Times]}
分支语句代码下载 le%&r