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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);
% U6 k) S4 V+ u8 F8 fSystem.out.print("# J( V2 b! l3 u; d& ~4 ]
目前共有"+count+"笔数据");
" C9 w) F; S% F! o7 HSystem.out.print("
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按任意键继续...");  2 n: w- U, `$ v
enter=bufin.readLine();  4 x8 x8 a& I( m
new str14(htable);  % _  F% k" V% \; B
break;  1 R. S! W* l  a/ t6 S8 ~
default:  9 l( W$ J6 O5 @, d+ H  Z
}  . [% Y( B2 h: _& U
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public int select() throws IOException//method of getting a function selector
# D! l6 r; [2 w  l{
0 S8 K/ E6 ?$ P0 k& }' P. n) wString input;  - _- R" C$ n# ]4 t3 ~! W
int value=0;  . {  G4 {" C6 t( ~8 B* n
input=bufin.readLine();//read a input from keyboard
' L+ |" t; E& ]  u" }# }* j5 gtry
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value=Integer.parseInt(input);//convert a string to a int value  . ^9 g) f3 M' m* i- |- I- j5 g
}catch(NumberFormatException e)//can’t vonverted  & o; }+ k  d- i& q! }; _; @9 O
{
% p2 E" V& ?$ [+ VSystem.out.print("请输入选项1~6:");
4 m4 N3 F; H9 |7 k" ]* Q8 qvalue=select();
6 n8 Q: L' t5 h" _5 N}
1 X0 S  H2 E, g" g& q4 Jif(value>6||value<1)//if exceed then print a message and reenter    E, P; Y6 B9 X1 ^$ }3 U& L8 \
{
  n$ ?# O0 Z$ T4 @$ }* t* ?System.out.print("请输入选项1~6:");  1 c0 Z& c/ H# K& p5 C4 u7 R
value=select();
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return value;//return a value  * \$ A# P5 m7 k
}
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3 {& @+ Y  f( _public int getid(int count)throws IOException//a method of return the number of data
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String input;
7 w  q3 u( z: }4 Z$ K" yint value=0;  ; b4 x' J6 Y. L9 e7 [1 i# W
input=bufin.readLine();//read a user input string from keyboard  6 J8 z. E3 s$ J6 r& Z
try  : Q* F% [" u0 p  q
{  6 F8 q" T; ^3 u# k5 d( B
value=Integer.parseInt(input);//convert the string to a int  ) g$ C4 K- J: c3 a9 W$ x
}catch(NumberFormatException e)//if can’t convert to a integer then reenter  3 Y7 e) o7 h+ A6 b+ m
{
, t) N1 N6 m! T  Y/ }# f2 @System.out.print("请输入数据编号:");
) B$ m2 g* k& ?( Jvalue=getid(count);
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if(value>count)//the input value is out of bound
8 {/ m0 c" J/ u, b+ S* x; O4 D{
. Y3 @  q& S: C& ~* k$ u! D7 J" zSystem.out.print("无此编号的数据,请重新输入:");
. i+ x% J3 P6 I; z7 y* Jgetid(count);  ! [2 b  o$ t+ O% W
}
1 g/ u  K2 g/ c! l: F3 u" i0 Z( C: ereturn value;//return a value  / v$ ~1 _! B! ]1 Q6 c8 p( Y  e' {
}  ! G5 a" q% e9 [' I5 O9 K
}

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