Help with TextFileInput

Hello, I'm new to the forums and to Java Programming. I have some questions about programs I'm writing with TextFileInput I have 5 programs to write by Monday so hopefully you guys can help me out :).

I finished writing the first program. Here it is:

Quote:

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import javax.swing.*;
import java.lang.*;
public class Lab5Program1 {

public static int inputFromFile (String filename)
{
TextFileInput in = new TextFileInput (filename);
int lengthfilled = 0;
String line = in.readLine();
while(line!=null) {
wordArray[lengthfilled] = line;
lengthfilled ++;
line = in.readLine();
}
in.close();
return lengthfilled;
}

public static String isOrIsNot, inputWord;
public static String wordArray [];

public static void main(String[] args) {
inputFromFile ("Lab5Input.txt");
while(true)
{
inputWord = JOptionPane.showInputDialog(null,"Enter a word in all lower case:");

if(inputWord.equals("Stop")) System.exit(0);
if (wordIsThere(inputWord,wordArray))
isOrIsNot = "is";
else
isOrIsNot = "is not";
JOptionPane.showMessageDialog(null,"The word "+inputWord+" "+
isOrIsNot+" on the list.");
}
}

public static boolean wordIsThere(String findMe, String[] theList){
for(int i=0;i<theList.length;i++){
if(findMe.equals(theList[i])) return true;
}
return false;
}
}

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However, when I compile it tells me that I have a "Null Point Exception". The problem lines (according to the compiler) are indicated in bold. Can anyone tell me how to fix it?

Anyone? I've been such on this for a long time and I still have four programs to go.

You need to initialize wordArray, i.e.

Code:

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public static String[] wordArray = new String[NUMWORDSNEEDED];

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You might be better of with an ArrayList<String> though... you don't seem to know exactly how many lines there are, as far as I can tell.

instead of .dat u make it .txt

import java.io.DataInputStream;
04.import java.io.FileInputStream;
05.import java.io.DataOutputStream;
06.import java.io.FileOutputStream;
07.import java.io.IOException;
08.
09.public class PrimitiveStreamExample {
10.
11. public static void main(String[] args) {
12. //
13. // Prepares some data to be written to a file.
14. //
15. int cityIdA = 1;
16. String cityNameA = "Green Lake City";
17. int cityPopulationA = 500000;
18. float cityTempA = 15.50f;
19.
20. int cityIdB = 2;
21. String cityNameB = "Salt Lake City";
22. int cityPopulationB = 250000;
23. float cityTempB = 10.45f;
24.
25. try {
26. //
27. // Create an instance of FileOutputStream with cities.dat as the
28. // file name to be created. Then we pass the input stream object
29. // in the DataOutputStream constructor.
30. //
31. FileOutputStream fos = new FileOutputStream("cities.dat");
32. DataOutputStream dos = new DataOutputStream(fos);
33.
34. //
35. // Below we write some data to the cities.dat. DataOutputStream class
36. // have various method that allow us to write primitive type data and
37. // string. There are method called writeInt(), writeFloat(),
38. // writeUTF(), etc.
39. //
40. dos.writeInt(cityIdA);
41. dos.writeUTF(cityNameA);
42. dos.writeInt(cityPopulationA);
43. dos.writeFloat(cityTempA);
44.
45. dos.writeInt(cityIdB);
46. dos.writeUTF(cityNameB);
47. dos.writeInt(cityPopulationB);
48. dos.writeFloat(cityTempB);
49.
50. dos.flush();
51. dos.close();
52.
53. //
54. // Now we have a cities.dat file with some data in it. Next you'll
55. // see how easily we can read back this data and display it. Just
56. // like the DataOutputStream the DataInputStream class have the
57. // corresponding read methods to read data from the file. Some of
58. // the method names are readInt(), readFloat(), readUTF(), etc.
59. //
60. FileInputStream fis = new FileInputStream("cities.dat");
61. DataInputStream dis = new DataInputStream(fis);
62.
63. int cityId = dis.readInt();
64. System.out.println("City Id: " + cityId);
65. String cityName = dis.readUTF();
66. System.out.println("City Name: " + cityName);
67. int cityPopulation = dis.readInt();
68. System.out.println("City Population: " + cityPopulation);
69. float cityTemperature = dis.readFloat();
70. System.out.println("City Temperature: " + cityTemperature);
71. } catch (IOException e) {
72. e.printStackTrace();
73. }
74. }
75.}

source: Java Examples - How do I use DataInputStream and DataOutputStream?

Quote:

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Originally Posted by nigamsir

instead of .dat u make it .txt
...
source: Java Examples - How do I use DataInputStream and DataOutputStream?

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How does that all apply to the NullPointerException mentioned by the OP?

kind regards,

Jos