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Thread: Reading the data from DataInputStream . help :(

  1. #1
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    Unhappy Reading the data from DataInputStream . help :(

    import javax.swing.JOptionPane;
    import java.util.*;
    import java.io.*;
    import java.lang.Exception.*;
    public class FinalNaTlga
    {
    		static Scanner input = new Scanner (System.in);
    		static final int PASSWORD = 1234;
    		static final int DONE = 143;
    		static final int EOF = -1;
     
    		public static void main (String [] args) throws FileNotFoundException,IOException, EOFException
    		{
    				DataOutputStream stream = new DataOutputStream(new FileOutputStream("Merchandise.dat"));
    				DataInputStream stream1 = new DataInputStream ( new FileInputStream ("Merchandise.dat.tmp"));
     
    				String s1 = "LBC";
    				String s2 = "JRS_Express";
    				String s3 = "MoneyGram";
    				String s4 = "Western_Union";
    				String choice, pcat = "", pname = "", mode, pay = "", pay2 = "";
    				int select, pass = 0,pass1,  pcode = 0, q = 1, chc2 = 0, num = 0, x = 0, y = 0, z =0, xx = 0;
    				char chc, md;
    				double pprice;
     
    			try {
     
    				System.out.print(" \n++ WELCOME TO SUPER ELF MERCH ++ ");
    				System.out.println(" \n===================================");
     
    			     do {
    				System.out.print("\nChoose user: \n\n[1] SHOP OWNER\n[2] BUYER\n>>> ");
    				select = input.nextInt();
     
    				if ( select == 1)
    				{
    						System.out.print("\n ** SECURITY CHECK **" + "\nEnter security password: ");
    						pass = input.nextInt();
     
    						if ( pass != PASSWORD)
    						{	
    								System.out.print("\nInvalid password.");
    								pass1 = 1;
    						}
    						else
    						{
    						 System.out.print("\n=============================\nHi Shopkeeper! Good day ! ^^\n=============================");
    				do {
    					System.out.print("\n\nWhat would you like to do this time?" + "\n[a] ADD INVENTORY" + "\n[b] MANAGE SALES" + "\n[c] EXIT");
    					System.out.print("\n>>> ");
    					input.nextLine();
    				        choice = input.nextLine();
    					chc = choice.charAt(0);
    					pass1 = 0;
     
    								switch (chc)
    								{
    								case 'a':case'A':	
    		//in this part, data here is entered and written through the data streams
    								System.out.print("\nINVENTORY");
    								do {
    								System.out.print("\nPress Enter to continue :) ");
    								input.nextLine();
    								System.out.println("\n++++++++++++++");
     								System.out.print("\nEnter product code or " + DONE + " to quit: ");
     								while (!input.hasNextInt())
    									{
    									System.out.println("\nInvalid data type!");
    									System.out.print("\nEnter product code or " + DONE + " to quit. >> ");
    									input.next();
    									}
    								pcode = input.nextInt();
    								while (pcode != DONE)
    								{
    								   input.nextLine();
    								   System.out.print("Enter category: ");
    								   pcat = input.nextLine();
    								   System.out.print("Enter product name: ");	
    								   pname = input.nextLine();
    								   System.out.print("Enter product price: ");	
    								   pprice = input.nextDouble();
     
    								stream.writeUTF(pcat);
    								stream.writeInt(pcode); 
    							        stream.writeUTF(pname); 
    							        stream.writeDouble(pprice);
     
    								System.out.print("\nEnter product code or " + DONE + " to quit: ");
     
    												while (!input.hasNextInt())
    												{
    												System.out.println("\nInvalid data type!");
    												}
    												pcode = input.nextInt();
    											} 
    											stream.close();	
    			q =  JOptionPane.showConfirmDialog(null,"Do you want to continue?","SELECT",JOptionPane.YES_NO_OPTION);
    										} while ( q != JOptionPane.NO_OPTION);	
    											break;
     
    	                                             case 'b':case'B':  
    //through here the data entered in case a, should be shown here. but in my case, it only shows null.                    	 
    	                                             	System.out.println("\nSALES\n\nCATEGORY\tPRODUCT NAME\t     PRODUCT CODE\tPRICE");										                                                                             System.out.println("======================================================================");
    											while ((pcode = stream1.readInt()) != EOF)
    											{
    												pcat = stream1.readUTF();
    												pname = stream1.readUTF();	
    												pprice = stream1.readDouble();						
    												stream.writeInt(pcode);
    												stream.writeUTF(pcat);
    												stream.writeUTF(pname); 
    												stream.writeDouble(pprice);			
     
    								System.out.println(pcode+ "\t\t" + pcat + "\t\t" + pname + "\t\t" + pprice);				
    											}
    											stream1.close();
    											break;
    									     case 'c':case'C':
    											break;
    									     default:
    											System.out.print("");	
    								} z = JOptionPane.showConfirmDialog(null,"Do you want to go back to the menu?","SELECT",JOptionPane.YES_NO_OPTION); 
    					} while ( z != JOptionPane.NO_OPTION);
    				}
     
    								File old = new File("c:\\java\\Mechandise.dat");
    								File temp = new File("c:\\java\\TempMerchandise.dat");			
     
    								old.delete();
    								temp.renameTo(old);			
    		}	pass1 = 0;
    				} while (pass1 = 0;
               }
              catch (Exception e)
              {
    	        System.out.print(e.getMessage());
    	        stream1.close();
    	        stream.close();
               }
     
          }
    }

    [edited]
    I dont really know what's wrong.

    the code here is actually a part of a code only
    The thing here is, I can actually write the data. But when it comes to reading it, it only shows null

    please help me . i really dont know what to do anymore .
    Last edited by cuihanluan; October 7th, 2012 at 05:57 AM. Reason: not direct to the point


  2. #2
    Super Moderator jps's Avatar
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    Default Re: Reading the data from DataInputStream . help :(

    it only shows null
    What shows null?
    If something shows null and you think it should not be null, go to the place where you thought you assigned a non-null value and add a println (or ten) and see what is going on.
    If that does not help you figure it out try to be more descriptive in stating your problem in terms of what values you are getting where in the code, and what values you expected at that point in the code. Use comments in the code to mark areas of interest you think are related to the problem.

  3. #3
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    Default Re: Reading the data from DataInputStream . help :(

    the data inputted through the dataoutputstream, wont show. it only shows null.

  4. #4
    Super Moderator curmudgeon's Avatar
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    Default Re: Reading the data from DataInputStream . help :(

    Is there a NullPointerException being thrown? If so, what line throws it? More information would help us quite a bit.

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