查看: 2774|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);
1 h7 z, w# T, ~4 ?System.out.print("
, L1 s" r* X- r目前共有"+count+"笔数据");
0 A+ \9 ^! A# E3 S( {System.out.print("% o( ~* ~: k6 ], z& a- G9 K& G0 g/ e

5 U" k" D2 U5 ~% J" U4 {按任意键继续...");  : K3 Q6 D7 a. P; U5 h- d
enter=bufin.readLine();  5 `7 D4 y' D4 k2 f: e! L
new str14(htable);
! V9 x% I) j/ j% H5 [1 cbreak;  % M  Y) A4 H! t7 D/ ^) P/ _3 U
default:
3 U* j5 X9 g6 e" N. m, i/ S* t7 i}  ' A4 K5 y* `# R* I" s
}
: A& G* q  S% k5 H
0 W9 v) ?- t0 g5 m/ @. Mpublic int select() throws IOException//method of getting a function selector  9 Y  q. Y! k9 U  a/ P# ~1 {
{  % z) I+ u, b/ Y# ?  v
String input;  & N$ i+ H* y3 s
int value=0;  ; |9 @3 }& }7 X( g+ ]* V
input=bufin.readLine();//read a input from keyboard  " D# v, V' K8 k
try
) O* g/ P5 I. F4 {{  5 |8 B/ @, A; E, }# r- X  s$ G2 r
value=Integer.parseInt(input);//convert a string to a int value
% a5 J$ m2 \/ z5 w" X6 u! _}catch(NumberFormatException e)//can’t vonverted  0 j2 ~1 m8 w, L2 O" @5 c5 r
{  3 s% q3 q% l( y) h, R$ n
System.out.print("请输入选项1~6:");
, ], }( U, a3 i1 b8 y! h: zvalue=select();
' y, l+ V" g+ n9 Z}
. P* J  I4 J! U: w1 ]% ^if(value>6||value<1)//if exceed then print a message and reenter
2 V9 [' E1 J4 O{
* P" ^8 a! A# b& QSystem.out.print("请输入选项1~6:");  0 w' K8 U" G* x9 M5 ~
value=select();    l8 B  L9 L& I2 F
}  : `+ l! ]: S  q' @% j% X
return value;//return a value  & d! T' e# G1 Z* \3 Q4 ~
}
+ G. O" m; W8 N# _3 u; s9 C$ h/ f9 {6 _) h
public int getid(int count)throws IOException//a method of return the number of data
$ X2 T. N; R0 \# y! S" E1 {2 h{  5 d9 Q" I# O0 q2 T( X; }# D
String input;
' R: Y+ i( \" F1 cint value=0;
3 _* [: N. V- m1 l% X; a1 linput=bufin.readLine();//read a user input string from keyboard  + D# S1 c9 L- D9 q
try
( _7 E+ I/ S7 K% d. b{  - C8 Q, g4 ]7 Q( `8 y1 d2 l
value=Integer.parseInt(input);//convert the string to a int  3 {* ?& c. L: W" c
}catch(NumberFormatException e)//if can’t convert to a integer then reenter
+ d( ]# p6 y" M0 t* m2 x{  : ?+ ^0 G: L/ `$ T9 u! b7 f
System.out.print("请输入数据编号:");  ; _6 ^2 a2 o$ s1 B* g% F) _
value=getid(count);
5 l1 p6 D" N% n7 j}
; I8 g0 R- _) ]" C5 Oif(value>count)//the input value is out of bound
! U5 P, @1 Y' h) B# |0 G{
' K2 G3 q4 @. O+ h! P$ S7 ZSystem.out.print("无此编号的数据,请重新输入:");  + D5 u* l) c5 J
getid(count);  9 P) Q1 q& b5 f# P3 b+ x
}
0 ^7 F7 g; ^' i! b; c5 qreturn value;//return a value  8 f! y" Z0 V. N1 m: d" x$ Y) c" d
}
. D1 a! R1 [1 e, {- e; s}