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标题: [转帖]Hashtable简易数据库程序 [打印本页]

作者: god 时间: 2005-3-31 01:45
标题: [转帖]Hashtable简易数据库程序
import java.io.*;
import java.util.*;
class str14
{
InputStreamReader stdin=new InputStreamReader(System.in);
BufferedReader bufin=new BufferedReader(stdin);

public static void main(String args[]) throws IOException
{
new str14();//run the application
}

public str14() throws IOException//constructor
{
Hashtable htable=new Hashtable(20,0.75F);
dataBase(htable);
}

public str14(Hashtable htable) throws IOException //override the constructor
{
dataBase(htable);
}

public void dataBase(Hashtable htable) throws IOException
{
int count=htable.size();//get the ammount of the data in htable
int value,id,num;
String key,enter,data;
Enumeration keys=htable.keys();//get all the key in htable
Enumeration elements=htable.elements();//get all the elements in htable
System.out.println("
Hashtable 简易数据库程序
");
System.out.println("(1)输入数据");
System.out.println("(2)请除所有数据");
System.out.println("(3)显示单笔数据");
System.out.println("(4)删除单笔数据");
System.out.println("(5)显示所有数据");
System.out.println("(6)结束程序");
System.out.print("请输入您的选择:");
value=select();//call select(),return the function number
switch(value)//the function
{
case 1:
System.out.print("
请输入一笔数据:");//need data input
data=bufin.readLine();
count++;
key=String.valueOf(count);
htable.put(key,data);//store it to the htable
System.out.print("
输入完成，按任意键继续...");
enter=bufin.readLine();
new str14(htable);//reenter
break;
case 2://clear all data from the htable
htable.clear();
System.out.print("
已删除了所有数据... 按任意键继续...");
enter=bufin.readLine();
new str14(htable);//reenter
break;
case 3:
System.out.print("
请输入要显示的数据编号:");
id=getid(count);//call getid()
key=String.valueOf(id);
Object select=htable.get(key);//fetch the data from the htable
data=select.toString();
System.out.print("
编号"+" "+"内容");
System.out.println("
"+key+" "+data);//display the data
System.out.print("
按任意键继续...");
enter=bufin.readLine();
new str14(htable);//reenter
break;
case 4:
System.out.print("请输入要删除的数据编号:");
id=getid(count);
key=String.valueOf(id);
htable.remove(key);//remove data
count--;
num=count;
System.out.print("已删除了所选择的数据...按任意见继续...");
Hashtable htable1=new Hashtable(20,0.75F);//create new htable named htable1
elements=htable.elements();//fetch all the data from htable
while(elements.hasMoreElements())
{
key=String.valueOf(num);//a new value
data=(String)elements.nextElement();//fetch content of the data
htable1.put(key,data);//store it to htable1
num--;
}
htable.clear();
enter=bufin.readLine();
new str14(htable1);
break;
case 5:
String[] sortkey=new String[count];//create a new sort array
String[] sortdata=new String[count];
num=count;
elements=htable.elements();
keys=htable.keys();
while(elements.hasMoreElements())
{
key=(String)keys.nextElement();//fetch value of key
data=(String)elements.nextElement();//fetch value of data
sortkey[num-1]=key;//store the value of key to sortkey array
sortdata[num-1]=data;//store the value of data to sortdata array
num--;
}
System.out.println("
编号"+" "+"内容");
for(int i=0;i<count;i++)//display all content after sorting
System.out.println(" "+sortkey+" "+sortdata);
% y5 |3 m8 |' ^" r+ r% _System.out.print("
8 ?. X3 _6 l9 O8 g! _; R" K目前共有"+count+"笔数据");
& }, a: I& c' p5 g4 u1 _System.out.print("
2 ~+ G% [( f$ \' n, q. m) e
3 J* o) t, k3 P4 P, F按任意键继续...");  & c: y* g* ?$ T, Y6 |# ?) w
enter=bufin.readLine();  * n) j& \; H* K
new str14(htable);
6 D4 O- |; |6 x; |6 O- Ybreak;
  _9 l( C2 u# ~* xdefault:  2 y1 @( Q% R, L# m* i% A" |
}
6 ^: X; I. s  f}  1 `2 d' M5 [: F' ?" i: ~+ S) \+ }
( k) m4 P% a, n. s9 W
public int select() throws IOException//method of getting a function selector
& J2 d# P+ [8 t6 e; |4 p{
& a2 H8 m3 T, h, BString input;  6 n8 O( V* }+ z2 ~  p+ D
int value=0;    L( p  f6 }4 G5 C
input=bufin.readLine();//read a input from keyboard
& e  W4 P" k6 D$ M9 W2 {try  ; X% i: t3 a8 l/ x( L9 `  K" W
{  $ u6 d2 w1 i, i! @* e; c1 O, f
value=Integer.parseInt(input);//convert a string to a int value  " A/ e" |# ^( U: W
}catch(NumberFormatException e)//can’t vonverted
$ O$ l1 p; W0 A( \5 g- }{
! J+ n2 w% u: b0 wSystem.out.print("请输入选项1~6:");
% ]  q7 i  e7 i! r( m- L$ L2 Svalue=select();
+ o+ {( f, r- L! Z}
& z* j4 W' c! f/ w2 x; @) r4 B6 f7 qif(value>6||value<1)//if exceed then print a message and reenter  ) w/ N. A0 M! C
{
0 L. f# ]+ p( ySystem.out.print("请输入选项1~6:");
value=select();  3 J2 R& x2 k  ^
}
6 Y1 `) G6 Q4 R  Preturn value;//return a value    |# _2 r3 v: p$ F6 ]7 z# Y7 O% E" Q
}  9 G  X* ]4 s3 g( \% Q* d

7 y- l4 L3 `& a" E% _public int getid(int count)throws IOException//a method of return the number of data
/ z2 Q- h  k; _8 P3 z0 L5 i{
# M  e7 ~2 p& Z) D1 c7 DString input;
& ~* R8 w$ b! v/ e; q8 T: D& L/ Zint value=0;  ; }2 E9 I4 q1 v) I7 I, @6 C8 M6 ?
input=bufin.readLine();//read a user input string from keyboard
2 y% {, A: g% A5 C1 y% T1 ~try  . R2 h8 M& T& |( X2 p0 t
{  ( v5 A; N- b, w( e# y/ U! j% n
value=Integer.parseInt(input);//convert the string to a int
4 G( ]9 R( Y- e$ N# F}catch(NumberFormatException e)//if can’t convert to a integer then reenter    F! ?/ s! F7 ~% s+ T- L9 }/ y
{
& e! D" b( \8 t4 G) A5 R, lSystem.out.print("请输入数据编号:");  5 I1 ~  f- V% g- f
value=getid(count);
* U. J% o* W/ q' t. n6 V}  * ~6 y& b: m1 u2 F" I* b
if(value>count)//the input value is out of bound  / l* y, T  I8 u& n/ B
{  3 X$ Q3 m* C% f  m
System.out.print("无此编号的数据,请重新输入:");  ' ]8 a4 V. I6 O% Z0 ?
getid(count);  0 r* P) e* y% ?  ?) N  ~% z
}  5 H  [- x- _% {- A- \4 a4 R" U3 s2 P
return value;//return a value  ! c. D  f+ {  d1 r7 F: N
}  5 O; ?9 o/ ~8 N
}

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