查看: 2734|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);  ; i9 X5 N0 S! M6 w. {) b
System.out.print("' j" |4 l. @- _9 i5 ^8 X; ]
目前共有"+count+"笔数据");  * u9 P$ i3 ]( b. Z2 M3 y
System.out.print("# ]9 F, s) C1 K
/ k# d" w+ [) H7 w& g+ q4 C
按任意键继续...");
( ^) \4 F# x7 u2 |6 \  f; senter=bufin.readLine();  * u& S; E* n! m/ _
new str14(htable);  6 @! n! i# Y8 U( k# T
break;
* \7 w- V- G) [3 e1 t' ?* Edefault:
9 p/ L  v: Z7 }0 F2 Q1 Q4 `}  , F; V, W6 S& f5 w" R
}
/ }& k+ i8 r" m- F& ~+ h7 }! t* p% a
public int select() throws IOException//method of getting a function selector
4 v/ ^/ A: Q. H) {$ r* y/ V{  0 w. y+ e& {( w. ~. i% V
String input;  7 S5 p! `; t4 O8 f
int value=0;
3 N! ~8 H- `' T. Z) b+ ?- D: L( Iinput=bufin.readLine();//read a input from keyboard
) f# {: _3 C1 ]5 x0 @try  ' y- {. A4 q- p+ Z- Y# l3 y
{
( M7 i8 b$ @! U6 J- o2 Svalue=Integer.parseInt(input);//convert a string to a int value
# F! U1 ?' k$ M5 A& }}catch(NumberFormatException e)//can’t vonverted  5 I: d2 w* i/ W3 Q: H
{  3 Q0 J3 E. u+ q. I  ?
System.out.print("请输入选项1~6:");  1 J- ~: C& }3 X! N' z
value=select();  . r" R  v9 W4 y' I
}  : _2 p& P. Y& _+ i% t! H9 h
if(value>6||value<1)//if exceed then print a message and reenter  ; \8 S! d4 i: m& i. z3 {/ j
{
3 ^+ H2 J5 O, k6 e6 k# ySystem.out.print("请输入选项1~6:");
. f+ J& b( V) h4 y+ s' J5 t2 ~4 X: evalue=select();
8 ~8 D6 Z; \1 p$ [( ^) V/ o1 A}  / i) G( G* a- u
return value;//return a value
7 R1 ]; U2 o/ ?3 U* `}  4 k# n: y3 v: X5 Q7 {: E( H( n
0 ]3 y% R7 k1 b( X8 J2 r, }( }
public int getid(int count)throws IOException//a method of return the number of data  * I/ S$ J9 d7 t3 o7 ~0 B# m* t
{  2 O( d! Z' A; u3 Q
String input;
/ B: d5 t  J' g9 f! Z  aint value=0;  . s, j# r3 C# u2 @& k' w
input=bufin.readLine();//read a user input string from keyboard  3 ]1 W8 Q, U8 o5 ?, e7 @: w) n
try
8 w" X; A1 {. Z/ y& x4 J) a{  8 c' }, A# h+ J4 n6 Q8 |
value=Integer.parseInt(input);//convert the string to a int
6 H2 i) m( ?% T9 V}catch(NumberFormatException e)//if can’t convert to a integer then reenter
6 d0 G+ F& H2 V! n) O$ W  z0 I{  8 ], ?. q: O  y
System.out.print("请输入数据编号:");  3 s3 j# Y4 l. t
value=getid(count);    Y) w, k9 D5 c6 s( P# B3 ]: y
}
# S" ?8 ]3 \! v+ E9 Aif(value>count)//the input value is out of bound  0 g% R2 W8 C% p4 s, B& ?" d
{  * Z3 t3 i9 {$ T
System.out.print("无此编号的数据,请重新输入:");
2 }9 A5 q- e$ W1 rgetid(count);
1 Q* Y. z9 k: t/ M9 G9 O9 [4 l1 |, v}  / w0 K3 B; y: F
return value;//return a value  ) b4 {+ u' n% G) J
}
7 `# \3 Q$ Y$ [9 p/ E}