查看: 2825|回复: 0

[转帖]Hashtable简易数据库程序

字体大小: 正常放大

god

206 主题	2 听众	882 积分

升级 70.5%

该用户从未签到

电梯直达

1^#

发表于 2005-3-31 01:45 |只看该作者 |正序浏览

|招呼Ta 关注Ta

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);  / [+ e" ^) N# d& O4 `5 N0 {
System.out.print("/ [2 v9 J, X! V) _9 ^) Y
目前共有"+count+"笔数据");
7 l6 `# D; Q9 D" JSystem.out.print("
8 T# l2 q1 `, e3 e) U4 i9 O5 t3 p8 l; B
按任意键继续...");  / g, y! ~! S0 r" K; I  h
enter=bufin.readLine();
4 D, h3 f1 g  H, |* D& {# [$ wnew str14(htable);  ( h! ?9 ]; y3 \6 q6 G) O; z- u
break;
; n" l0 i4 R3 Rdefault:
$ k" c0 p) W" N/ B# l" G* m}  ) Q  G- \4 S% n1 m# `
}  2 B! P8 f# u3 i

( F: q  O2 ]' U+ ~! [. @public int select() throws IOException//method of getting a function selector
+ W$ A" y; Y( t( ~$ d5 s{
9 V- g4 M% d* X8 a3 d! x5 Z# wString input;  7 y5 G5 B. q+ G# _  @4 V
int value=0;
; n* A2 b% e* d9 K$ L9 m1 A) Y+ ?input=bufin.readLine();//read a input from keyboard
3 j# A- A! n* r. w+ ~. t+ j5 z3 q4 vtry  + v2 [" g, H% P- J! T
{
( x# v# u6 Z8 q6 k# c+ c- J; C4 _value=Integer.parseInt(input);//convert a string to a int value
: J/ m4 T5 ?7 I2 L4 e# {7 W4 s}catch(NumberFormatException e)//can’t vonverted
& x$ J" ]: J; b0 @- A* u, O{
  g4 [5 f& W" r( E% e" ?System.out.print("请输入选项1~6:");  , l3 `1 D( s# z+ f, _! |2 p! N! v
value=select();  0 H# }) z: F2 l
}  : w' ^0 B- u+ L0 e
if(value>6||value<1)//if exceed then print a message and reenter
9 u3 b5 H; f  a9 q{
% c5 l6 A% S, y2 b6 pSystem.out.print("请输入选项1~6:");
( L" D8 V8 Y9 R5 Nvalue=select();    ~- J! o* v0 a/ r6 }
}  2 d0 w2 e5 W. p/ \8 P  N( ^
return value;//return a value
6 G9 A4 A+ \6 B' I& O/ ]3 L3 G1 b}  9 w5 P" w  j/ ^

# j  t) |/ i3 J- D4 j  Zpublic int getid(int count)throws IOException//a method of return the number of data  - w2 l/ L# C6 X$ l5 g1 d& o4 D& A% h
{
9 u* }1 C* v$ ?0 y! B+ S2 w2 R+ _String input;  % e2 M3 a7 t6 z& g
int value=0;    C7 G. Y0 Z% {, b! o/ V
input=bufin.readLine();//read a user input string from keyboard
" a1 W( M) I- Ktry  & `  @2 ^/ v& E3 @1 P
{
6 I# A7 y: Q; i9 p% h0 w+ E8 X( tvalue=Integer.parseInt(input);//convert the string to a int  / J' v9 s* {; T4 x2 g
}catch(NumberFormatException e)//if can’t convert to a integer then reenter
" h0 U- Y+ [% F{
3 {  V$ ]0 `8 jSystem.out.print("请输入数据编号:");
. v0 j' e% z, q; h! B5 jvalue=getid(count);
1 R  D7 ^; b7 n}
: ]' V) ^) R3 k& Qif(value>count)//the input value is out of bound
% L# |5 k$ A' Z{  ! u0 V% k7 b8 L' L- l/ v
System.out.print("无此编号的数据,请重新输入:");
) W, q6 B, t+ j5 [6 t+ qgetid(count);
2 R+ {. l3 p6 V0 c" g7 H}
; x+ d) r2 Z$ f. N; C$ Mreturn value;//return a value
, |; b6 D& y! G8 I}    c2 F- l' `7 x
}