全新java初学者实践教程6(Java SE5.0版)
ci <`*>l 基本语法3
u+~Ta YFL9Q< Ir }r98lz 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 @ :S<8 +K])&}Dw [font="Times] 1.循环语句[font="Times]:while,do-while,for
inBBU[Sl D}r,t_]Eb [font="Times]2.分支语句[font="Times]:if-else,switch,
bT2 b)nf [font="Times]
2r^| 3.跳转语句[font="Times] break,continue,label: 和[font="Times]return
udMDE=1~L [font="Times]
V \,Z ( 4.异常处理语句[font="Times]:try-catch-finally,throw
_t_X` mvyqCOp 0 实践:
_jQ"_Ff [font="Times] 1.循环语句
4jfkCU [font="Times] while 语句
6V
KsX+sd [font="Times]class While {
Uo#%f+t [font="Times]public static void main(String args[]) {
MD%_Z/NL [font="Times]int n = 10;
51u8.%{4 [font="Times]while(n > 0) {
!U/iY%NE [font="Times]System.out.println("tick " + n);
]g2Y/\)a [font="Times]n--;
]'3e#Cqeh [font="Times]}
E9!u|&$S [font="Times]}
S~.:B2=5K [font="Times]}
nb9qVuAGU [font="Times] do…while 语句
^w/_hY!4/ [font="Times] class DoWhile {
lU`]yL [font="Times]public static void main(String args[]) {
K!VIY|U [font="Times]int n = 10;
_=Ed>2M)no [font="Times]do {
NjIe2)}' [font="Times]System.out.println("tick " + n);
8%nb1CA [font="Times]n--;
gBA
UrY%] [font="Times]} while(n > 0);
6hv4D`d;o [font="Times]}
W2e~!:w [font="Times]}
u[$ \
az7 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。
+1zCb=;!{ [font="Times] for语句
!~u;CMR [font="Times] class ForTick {
NpG5$? [font="Times]public static void main(String args[]) {
wu"6Kyu [font="Times]int n;
(p08jR
'5 [font="Times]for(n=10; n>0; n--)
id="\12Bw [font="Times]System.out.println("tick " + n);
na,j [font="Times]}
2>Bx/QF@< [font="Times]}
K4b#
y~@ 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。
Dm?>U1{ 还有啊,[font="Times]for循环的部分可以为空的
8M9 &CsT6 [font="Times]class ForVar {
j'Z};3y [font="Times]public static void main(String args[]) {
eLXG _Qb" [font="Times]int i;
U ?P5cN [font="Times]boolean done = false;
W 0%FZ0l [font="Times]i = 0;
$@<qaR{t \ [font="Times]for( ; !done; ) {
9tvLj5~ [font="Times]System.out.println("i is " + i);
[XK Ke [font="Times]if(i == 10) done = true;
TR/'L!EE [font="Times]i++;
|!NKKvf [font="Times]}
L
s6P<"V [font="Times]}
k7yQEU [font="Times]}
循环语句的例子下载 k\W%^Z [font="Times] 2.分支语句[font="Times]
[HGGXgN [font="Times] if/else语句
.]}kOw:(# [font="Times]class IfElse {
{1,]8!HBJ [font="Times]public static void main(String args[]) {
+`O8cHx [font="Times]int month = 4; // April
{h5 S=b [font="Times]String season;
;O5p>o [font="Times]if(month == 12 || month == 1 || month == 2)
6Y<'Lyg/ [font="Times]season = "Winter";
_R-[*ucq [font="Times]else if(month == 3 || month == 4 || month == 5)
L5=Tj4` [font="Times]season = "Spring";
{KYbsD [font="Times]else if(month == 6 || month == 7 || month == 8)
m`l3@Z [font="Times]season = "Summer";
]@)T] [font="Times]else if(month == 9 || month == 10 || month == 11)
/*\pm!]._^ [font="Times]season = "Autumn";
, v,mBYaU [font="Times]else
<8nl}^d5 [font="Times]season = "Bogus Month";
eJFGgJRIvF [font="Times]System.out.println("April is in the " + season + ".");
iTJSW [font="Times]}
3)ac
[font="Times]}
Z".mEF-b [font="Times]//这段程序输出[font="Times]:
!mLQdkTE [font="Times]//April is in the Spring.
o7Ms]AblT [font="Times]// 注意[font="Times] “[font="Times]||”是或运算
[zmx [font="Times] switch语句
}GX[N\$N [font="Times] class Switch {
SA@MJ>Z [font="Times]public static void main(String args[]) {
02OL-bv}HS [font="Times]int month = 4;
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