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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);
. o. Z# p7 t1 D# ?% E9 @3 {System.out.print("6 J- o& |9 q8 {3 \/ g
目前共有"+count+"笔数据");  & S8 p) r* n3 M
System.out.print("
( W1 K. R# l4 @  K  q4 T1 M+ n! M7 P# f7 ~  \& {* n9 j  R
按任意键继续...");
0 j6 S9 E$ ]! G" w, eenter=bufin.readLine();  7 `3 |& \- w9 l) ~1 Z
new str14(htable);  5 X. n' Q0 i% O0 [8 D! N  J
break;
$ q1 E# ]! `- w: H- O" vdefault:
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- {% M' w! @/ R8 U* r4 V; T& fpublic int select() throws IOException//method of getting a function selector
7 E) S1 t0 A8 V0 T. w% L% H{
$ }0 g5 H! t! a( oString input;
3 R! j% t' }/ b9 kint value=0;  + j6 @9 j4 Z7 M7 d
input=bufin.readLine();//read a input from keyboard  0 V( u9 }/ H9 A: V, _( [% n
try
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value=Integer.parseInt(input);//convert a string to a int value  + A! M$ K4 g$ ?+ E4 r
}catch(NumberFormatException e)//can’t vonverted
8 M# t6 ?$ l* A) j* W2 ^* z+ ~0 i{
9 A1 Y$ _% w; E2 V- u# oSystem.out.print("请输入选项1~6:");
& L+ ~2 W" S/ }8 C" rvalue=select();  - s# {( @6 ~) L9 l: M5 T$ g3 `2 A
}
+ r: v% Z! V# L9 s  Pif(value>6||value<1)//if exceed then print a message and reenter
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System.out.print("请输入选项1~6:");
4 G& q3 s. X6 M" Q) Wvalue=select();  . F+ |5 S) ~5 d% a! ~% `3 j6 n
}
' P# u+ t5 D, F3 Dreturn value;//return a value
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  t& A' n! C( Zpublic int getid(int count)throws IOException//a method of return the number of data
+ _6 ?2 h+ n+ s$ i# a; V{  ( }0 t$ `. @# I2 M$ B2 S% y, _
String input;  4 X/ X2 ?2 V1 W( a& q1 B
int value=0;  ; S# A- I  e1 ?9 N
input=bufin.readLine();//read a user input string from keyboard
! y5 \$ K1 ?" dtry  ! `; i5 [4 {' G, O  f' B8 r- L
{  ( u0 V2 ^4 X- l5 q# g
value=Integer.parseInt(input);//convert the string to a int
5 f) P/ @# B" |# c' I}catch(NumberFormatException e)//if can’t convert to a integer then reenter
2 g, G6 y+ ]" S4 D" j% L{
; X' l; I1 l, C3 d3 J. iSystem.out.print("请输入数据编号:");  5 ?1 r7 w, S9 ~$ Y! A" u2 j7 W
value=getid(count);
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if(value>count)//the input value is out of bound  8 J- k, y+ }/ O( N9 t# M) @8 d: s
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System.out.print("无此编号的数据,请重新输入:");  2 G) ]# |1 Z- X8 \( V0 O1 t$ A
getid(count);
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return value;//return a value  - M/ u1 W( i. P1 W# P" L
}
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