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.Hashtable 簡易數據庫程序 "); System.out.println("(1)輸入數據"); System.out.println("(2)請除所有數據"); System.out.println("(3)顯示單筆數據"); System.out.println("(4)刪除單筆數據"); System.out.println("(5)顯示所有數據"); System.out.println("(6)結束程序"); System.out.print("請輸入您的選擇:"); value=select();//call select(),return the function number switch(value)//the function { case 1: System.out.print(" 請輸入一筆數據:");//need data input data=bufin.readLine(); count++; key=String.valueOf(count); htable.put(key,data);//store it to the htable System.out.print(" 輸入完成，按任意鍵繼續..."); enter=bufin.readLine(); new str14(htable);//reenter break; case 2://clear all data from the htable htable.clear(); System.out.print(" 已刪除了所有數據... 按任意鍵繼續..."); enter=bufin.readLine(); new str14(htable);//reenter break; case 3: System.out.print(" 請輸入要顯示的數據編號:"); 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(" 編號"+" "+"內容"); System.out.println(" "+key+" "+data);//display the data System.out.print(" 按任意鍵繼續..."); enter=bufin.readLine(); new str14(htable);//reenter break; case 4: System.out.print("請輸入要刪除的數據編號:"); id=getid(count); key=String.valueOf(id); htable.remove(key);//remove data count--; num=count; System.out.print("已刪除了所選擇的數據...按任意見繼續..."); 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(" 編號"+" "+"內容"); for(int i=0;i<count;i++)//display all content after sorting System.out.println(" "+sortkey[i]+" "+sortdata[i]); System.out.print(" 目前共有"+count+"筆數據"); System.out.print("
按任意鍵繼續..."); enter=bufin.readLine(); new str14(htable); break; default: } }
public int select() throws IOException//method of getting a function selector { String input; int value=0; input=bufin.readLine();//read a input from keyboard try { value=Integer.parseInt(input);//convert a string to a int value }catch(NumberFormatException e)//can’t vonverted { System.out.print("請輸入選項1~6:"); value=select(); } if(value>6value<1)//if exceed then print a message and reenter { System.out.print("請輸入選項1~6:"); value=select(); } return value;//return a value }
public int getid(int count)throws IOException//a method of return the number of data { String input; int value=0; input=bufin.readLine();//read a user input string from keyboard try { value=Integer.parseInt(input);//convert the string to a int }catch(NumberFormatException e)//if can’t convert to a integer then reenter { System.out.print("請輸入數據編號:"); value=getid(count); } if(value>count)//the input value is out of bound { System.out.print("無此編號的數據,請重新輸入:"); getid(count); } return value;//return a value } }
