查看: 2780|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 |倒序浏览

|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);  - x  a8 ?  v* f
System.out.print(". R1 \) y( w$ y4 c& z4 @+ K4 G
目前共有"+count+"笔数据");
- T- o, n8 C' ^System.out.print("6 l* |0 P, ~2 f6 r0 R1 S
; K% V( F0 E& a+ ~; }0 A2 z
按任意键继续...");
  c7 I. p! L/ s9 ]enter=bufin.readLine();
, `! N+ f, [7 |8 g3 U8 p) S8 }; tnew str14(htable);
) m0 i* r# p+ L/ _break;
  a. F- y6 Z+ w" E7 z$ A& gdefault:
" F$ }# d. l3 X. `5 ^! l1 k}
' T$ r$ P- K* Z' d) {1 z( \}
" ?2 D$ D9 I+ h* _1 s$ g1 \# h. h3 K' ^( q! k  o1 ?3 ^
public int select() throws IOException//method of getting a function selector  7 |& h, C; [) _* Y3 m7 T1 m
{
4 [# n1 N! ~+ d- @. w. ?; r* |8 XString input;  1 a. I7 W* g& T- `) O- e& G
int value=0;  & Z  q9 b% N* B. L7 h  J4 h: I
input=bufin.readLine();//read a input from keyboard
& ?" f$ I/ M; }try  ! x9 Z" K' \* z/ w) J
{  5 @$ a3 z/ ]2 _2 B  R
value=Integer.parseInt(input);//convert a string to a int value  5 m" S3 N- g: X) x' J: g
}catch(NumberFormatException e)//can’t vonverted
7 {% O& v& J5 k5 n( s" R8 k# `& k{
/ q' G. U6 c5 bSystem.out.print("请输入选项1~6:");  1 d' [  i7 U# c4 p  I
value=select();
& S  L7 @& |1 Q6 F2 R}  . H( D3 Z* F; t3 x; f3 \
if(value>6||value<1)//if exceed then print a message and reenter  4 S1 ~: x, f' B' `  o
{  / u' |6 L; n& _+ e
System.out.print("请输入选项1~6:");
% C; h  L1 |( tvalue=select();
8 f' K) M% f/ e: T# W0 y}    ?4 I# E7 w7 u' Y; c# s
return value;//return a value
, s! k3 j$ X" ?+ |. V+ a* e}
: _5 g7 d1 n" r, Q9 {% f
7 D+ b3 N( r% S5 qpublic int getid(int count)throws IOException//a method of return the number of data    d% e# R' b* g9 H+ g5 c
{
: @3 r( x/ I# s$ r, \String input;  " F+ O. |4 j. S
int value=0;    a. V3 A8 l1 N
input=bufin.readLine();//read a user input string from keyboard  4 I4 j6 I9 M$ e. e, W8 G+ C: }9 E5 ~
try  # q+ |: e: [9 V7 {' }  a' U
{  % \* B2 G7 P& @9 P$ Y
value=Integer.parseInt(input);//convert the string to a int  ! K7 x& y, H9 Z; G
}catch(NumberFormatException e)//if can’t convert to a integer then reenter  : X0 I) b7 @& j' _' O+ i
{  1 q) \' T" U1 C& ~( b1 I; R
System.out.print("请输入数据编号:");
) s5 Q1 ~# R3 i; u( w2 fvalue=getid(count);
. A2 p& a1 N; y: w( R- S/ e+ ?}
* G! T/ w1 X4 m  }& D. Gif(value>count)//the input value is out of bound  ) o% E/ b4 x, g% k+ r: q' j( G
{  + \- V3 k/ E  M2 D% e! J1 G  p: i
System.out.print("无此编号的数据,请重新输入:");
( j& I1 r9 C) W: y/ H5 x: D9 C& R! Agetid(count);
4 G+ T1 L' X% e9 e( r& ~1 ?}
0 Q& B& @/ c1 J- o% [; d) a! W; yreturn value;//return a value  ( t& i% ~. u$ K7 u
}  7 f) I/ n* j6 H6 I# v* K+ H0 \: s
}