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[转帖]Hashtable简易数据库程序

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电梯直达

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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);  ! g. [6 D. b7 R2 j7 W. O! N
System.out.print("
& v( c; j+ D! G2 d( _& z$ S目前共有"+count+"笔数据");
/ I+ `9 X- ]3 K4 \8 V. {' dSystem.out.print("$ `  ?" q% Q  o
2 S- x( o  N2 H; ?  B! t4 n' s  x
按任意键继续...");
+ Y- K* Z, K2 G2 g. Y5 X- }$ m& d6 Nenter=bufin.readLine();
- {3 G3 W( e& E" g% knew str14(htable);  3 C% Y! u; l, f0 ]. l8 {
break;
9 t" v' i* U! J; w! g8 z+ p$ vdefault:
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- \7 t* B1 W7 j4 F$ ]0 N
% k  K; g) u; j, Vpublic int select() throws IOException//method of getting a function selector
& B. F$ N  y" v2 c5 _" f3 V1 i! ~# o{  # R6 ~) P9 D0 m" @2 h* H+ {
String input;
5 j0 q- r- A# R& c9 a! W' L1 O$ lint value=0;  , ~0 ]9 k) M! W
input=bufin.readLine();//read a input from keyboard  % R5 m! r, @: x
try  ) V  d" i3 \1 A; B
{
6 |  \1 C$ q0 ~7 C0 H, Ovalue=Integer.parseInt(input);//convert a string to a int value    {0 U& B, O$ j: V
}catch(NumberFormatException e)//can’t vonverted  2 M7 z9 N. N3 i+ s+ Y
{
+ |6 S* x+ U2 t4 ESystem.out.print("请输入选项1~6:");  / @3 ^" {5 i  I0 I+ N/ x
value=select();  & i6 \0 N- M% b7 Z8 [% U
}  6 M) g7 X. u, h7 R
if(value>6||value<1)//if exceed then print a message and reenter  9 b& Q3 I! v: `8 J& S
{  # H) \6 D2 ~, D$ H; q% K
System.out.print("请输入选项1~6:");
) H0 ~1 [, k/ s% u2 v1 Wvalue=select();
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return value;//return a value  5 l" W8 \& }% y% @
}  # c2 \- I( T# ~# j# i6 f7 f& q

! P# Z; R" L4 ?- v" X' V* M: Bpublic int getid(int count)throws IOException//a method of return the number of data
2 u- e& b7 @& r0 r4 y{
: \( D' J, y) J# v1 y2 L1 hString input;  3 C! k# n+ L8 w
int value=0;  - ]; a. |4 e3 O9 D: f0 L
input=bufin.readLine();//read a user input string from keyboard
1 s, E2 T( ^" x% `' i+ Gtry
( ^8 p* ]2 c4 U$ \$ E{
$ Q# {: v/ n) Q6 Y4 Dvalue=Integer.parseInt(input);//convert the string to a int  : n# E6 {8 b/ a# z
}catch(NumberFormatException e)//if can’t convert to a integer then reenter  ) L* l4 [! k; R; u- v% e3 M5 T3 @& z
{
" J# e( {+ B1 n. s) O/ h6 j7 |System.out.print("请输入数据编号:");
$ `$ N: P# u+ o0 ]; ~6 n1 C, Cvalue=getid(count);  3 q1 V9 r" ~, F5 G6 A4 ~/ k
}
4 D; c* h' F- i, Y( h/ f+ p& P- zif(value>count)//the input value is out of bound  6 J* H, s! ^  t- T
{  4 H3 |" ^: R9 C5 L' A; V9 y: O& J
System.out.print("无此编号的数据,请重新输入:");  * C2 @+ T+ Q" X0 y- X+ M) I
getid(count);    P1 F+ o1 \% t% f
}  % I8 B6 _. ]8 e) V( i  c$ I
return value;//return a value
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