数学建模社区-数学中国

标题: [转帖]Hashtable简易数据库程序 [打印本页]

作者: god 时间: 2005-3-31 01:45
标题: [转帖]Hashtable简易数据库程序
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);
3 K: I/ O& L; X3 H3 h" MSystem.out.print("  O9 x: V) j& ?' H
目前共有"+count+"笔数据");
  o% A3 f+ I- tSystem.out.print("' j! p8 e$ ?) ^# J( J: [

* c$ ^1 J) u  ^6 R按任意键继续...");  / V/ u0 {0 J; b" j9 o  O
enter=bufin.readLine();  7 R6 s9 ]: j: ?, m( m2 B1 `
new str14(htable);  7 F" i. K5 w% s5 P6 T2 t
break;
* v& z: M) W2 K+ l- H# kdefault:
$ r# O, T5 Z3 S}  , E/ \- o# z8 t- J' u
}  : m2 F# Z; _) G" ^! J$ T

7 H8 o' S& v* X" Mpublic int select() throws IOException//method of getting a function selector
6 s: X1 T# h6 s* o3 y{
8 T( k2 E7 g# h: Z2 B( J2 n# i' ZString input;  3 `% q& R& C8 y9 _- D8 T- r) F3 |
int value=0;  " d$ Z2 `+ W: Z1 A8 `* f
input=bufin.readLine();//read a input from keyboard  - l  S9 d& f' V. H  E  W( b
try  9 z1 z: b4 u' }4 p0 y$ j
{
7 L6 z; o/ r" p. f! F3 L* Qvalue=Integer.parseInt(input);//convert a string to a int value  " \  ]% l$ Q% S9 M
}catch(NumberFormatException e)//can’t vonverted
8 }& j1 {. e  a% H0 P+ E{  " o9 H* C3 ?5 ~# O* a' u  o
System.out.print("请输入选项1~6:");
) n! \4 E: }+ |! ^! h7 P% N# fvalue=select();
9 j) [  F' |! D7 X. t) e}
) o; L- |6 o5 r+ P3 \4 U& X% iif(value>6||value<1)//if exceed then print a message and reenter
5 h0 u1 D' A0 K% X$ l{
9 k( z0 y# k7 a( j7 G5 ^System.out.print("请输入选项1~6:");
( v- I2 |2 m* N% ~; G* ?value=select();  ) b* v# D: O6 y  u' h& e( K
}  / {! Y# j( \1 \# D
return value;//return a value
- [  D( g+ P) i. B/ M" k}
6 \: R' K) G, I) ~) S
& L, z; E" U7 h/ y. L! r+ g9 Kpublic int getid(int count)throws IOException//a method of return the number of data  / s# p# O5 k$ V
{  6 S+ w& ^  v4 ]" `
String input;  : E) v5 [. A- \9 G: O/ N1 S
int value=0;
. P2 d4 l  T! a2 q% r) K! n" minput=bufin.readLine();//read a user input string from keyboard
3 y  O( \& c/ F) ]try  ' s/ b) u2 m$ C1 `  J& L- P! q
{
! E, A+ Z) `: u0 Ovalue=Integer.parseInt(input);//convert the string to a int  ! Q7 L3 F* q% a, B7 y. ]
}catch(NumberFormatException e)//if can’t convert to a integer then reenter
( _3 Z1 H) M2 k! E) N1 X{    |/ B* _1 p' g/ N/ ^( v
System.out.print("请输入数据编号:");  9 A1 j: R$ y* B" X0 n( S
value=getid(count);  0 h8 s# e+ q) f9 ]3 u& V
}
. L3 p+ }1 o% aif(value>count)//the input value is out of bound
5 Q& G/ ~0 ^! H4 ]3 R5 a{  6 J9 _  S+ U/ V% O* D
System.out.print("无此编号的数据,请重新输入:");  0 C- O/ ^! n6 }1 W  l
getid(count);
) ^3 A. k& U2 E  _}
; }* m& u/ w! W# A% ]6 ?2 U# }; Zreturn value;//return a value  2 n# j( T9 ^. N6 p3 o
}  / f; r5 h# p1 o! Y, B, H
}

欢迎光临数学建模社区-数学中国 (http://www.madio.net/) Powered by Discuz! X2.5