全新java初学者实践教程6(Java SE5.0版)
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],){ 基本语法3
vx}W.6C} *5d6Q W?X3 :1c9: 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:
eq,`T; O8)N`#1>+ [font="Times] 1.循环语句[font="Times]:while,do-while,for
#9CLIYJAd {W$K@vuV;? [font="Times]2.分支语句[font="Times]:if-else,switch,
(fcJp)D [font="Times]
-)Of\4kx 3.跳转语句[font="Times] break,continue,label: 和[font="Times]return
#VynADPs`o [font="Times]
/nB|Fo_&Q 4.异常处理语句[font="Times]:try-catch-finally,throw
_BHEK 'e:(61_ 实践:
LZ<^b6Dxk [font="Times] 1.循环语句
]oxi~TwY^ [font="Times] while 语句
4rrR;V"} [font="Times]class While {
]..7t|^b& [font="Times]public static void main(String args[]) {
'mO>hD`V [font="Times]int n = 10;
jchq\q)_z [font="Times]while(n > 0) {
Aqo90(jffx [font="Times]System.out.println("tick " + n);
r>cN,C [font="Times]n--;
njckPpyb@ [font="Times]}
E D^0t [font="Times]}
aDda&RM [font="Times]}
uS7kkzt-x [font="Times] do…while 语句
_(F8}s [font="Times] class DoWhile {
ubUVxYD? [font="Times]public static void main(String args[]) {
]8CgHT[^7 [font="Times]int n = 10;
qrufnu5cC [font="Times]do {
HMmB90P` [font="Times]System.out.println("tick " + n);
iB#*XJ;q [font="Times]n--;
lb\VQZp!y [font="Times]} while(n > 0);
.JX9(#Uk [font="Times]}
DhD^w;f] [font="Times]}
D";@)\jN 二者区别,[font="Times]do…while至少循环一次,而[font="Times]while的表达式要是为[font="Times]flase的话可以一次也不循环。再通俗一点,[font="Times]do…while就算是括号里的是[font="Times]flase,人家最少也能[font="Times]do一次。
^]MLEr!S [font="Times] for语句
~DP_1V? [font="Times] class ForTick {
ZY=a[K [font="Times]public static void main(String args[]) {
tr|)+~x3 [font="Times]int n;
_)[UartKx [font="Times]for(n=10; n>0; n--)
3@\J#mR
[font="Times]System.out.println("tick " + n);
#jM-XK [font="Times]}
Bu"5NB [font="Times]}
T,h9xl9i 与上面那两个的区别,[font="Times]for循环执行的次数是可以在执行之前确定的。通俗一点说吧,看这个例子[font="Times] for(n=10; n>0; n--)就是在括号里的时候,就已经知道要循环[font="Times]10次了。
wEC,Mbn 还有啊,[font="Times]for循环的部分可以为空的
b)@rp [font="Times]class ForVar {
uF+0nv+ [font="Times]public static void main(String args[]) {
_
o.j({S [font="Times]int i;
L :Ldk [font="Times]boolean done = false;
n50WHlMtt [font="Times]i = 0;
:B:6ezDF6 [font="Times]for( ; !done; ) {
SM\qd4 [font="Times]System.out.println("i is " + i);
i>e?$H,/ [font="Times]if(i == 10) done = true;
VhN 6
oI [font="Times]i++;
EO%"[k [font="Times]}
'9!J' [W [font="Times]}
J?C:@Q [font="Times]}
循环语句的例子下载 u=t.1eS5 [font="Times] 2.分支语句[font="Times]
S? #6{rx [font="Times] if/else语句
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d[jqk [font="Times]class IfElse {
%rJ'DPs [font="Times]public static void main(String args[]) {
GA;h7 [font="Times]int month = 4; // April
7=gcdfW,;x [font="Times]String season;
UCJx{7 [font="Times]if(month == 12 || month == 1 || month == 2)
9_fbl:qk;\ [font="Times]season = "Winter";
p0hE`! [font="Times]else if(month == 3 || month == 4 || month == 5)
E8BIb 'b; [font="Times]season = "Spring";
&O#,"u/q` [font="Times]else if(month == 6 || month == 7 || month == 8)
|#yH,f [font="Times]season = "Summer";
.FG%QF F~ [font="Times]else if(month == 9 || month == 10 || month == 11)
us+z8Mz [font="Times]season = "Autumn";
H*Tzw,f~ v [font="Times]else
nF$HWp> [font="Times]season = "Bogus Month";
:0Z\-7iK [font="Times]System.out.println("April is in the " + season + ".");
ih-J{1 [font="Times]}
jl5&T{z [font="Times]}
)Z)Gb~G [font="Times]//这段程序输出[font="Times]:
Ub/ZzAwq [font="Times]//April is in the Spring.
|-L7qZu% [font="Times]// 注意[font="Times] “[font="Times]||”是或运算
@qEUp7W.? [font="Times] switch语句
rn/~W[ [font="Times] class Switch {
.3&(Y [font="Times]public static void main(String args[]) {
&f2:aT) [font="Times]int month = 4;
/36gf [font="Times]String season;
%j.n^7i]^: [font="Times]switch (month) {
I-#7Oq:Np [font="Times]case 12:
)D ~ 5 [font="Times]case 1:
K&eT*JW> [font="Times]case 2:
aYn5AP'PH [font="Times]season = "Winter";
k-^le|n9 [font="Times]break;
2T(7V[C%9 [font="Times]case 3:
fbD,\ rjT [font="Times]case 4:
cQ
|Q-S [font="Times]case 5:
G.`},c;A- [font="Times]season = "Spring";
b!bg sd [font="Times]break;
voQJ!h1 [font="Times]case 6:
`aTw!QBfG [font="Times]case 7:
PQp/&D4K [font="Times]case 8:
0TZB}c#qT [font="Times]season = "Summer";
sUU[QP- [font="Times]break;
.N( X.C [font="Times]case 9:
Q[?R{w6 [font="Times]case 10:
"By$!R-& [font="Times]case 11:
> l]Ble [font="Times]season = "Autumn";
Ft?eqDS1 [font="Times]break;
V>/,&~0 [font="Times]default:
vn!5@""T [font="Times]season = "Bogus Month";
hQ'W7EF [font="Times]}
+abb[ [font="Times]System.out.println("April is in the " + season + ".");
%z=:P{0UQ [font="Times]}
ka6E s~ [font="Times]}
分支语句代码下载 %-a;HGbZn `mA;1S [font="Times]switch语句适合于条件非常多的逻辑
]6M,s0 请看上述语句可以混合使用,请看
下载例子