Develop Reference

Write and Read file with RandomAccessFile in Java

Hello I am writing a program that write and read file XML in Java.
Here is the Writing file
public static void main(String[] args) throws IOException {
File file = new File("C:\\Test\\employee.XML");
RandomAccessFile randomAccessFile = new RandomAccessFile(file, "rw");
//int codeEmp = 0;
String nameEmp[] = {"Name A", "Name B", "Name C", "Name D", "Name E"};
String addEmp[] = {"Address A", "Address B",
"Address C", " Address D",
"Address E"};
int saleEmp[] = {2000,1232,7653,1236,3452};
int comEmp[] = {400,100,3000,300,500};
StringBuffer buffer;
StringBuffer buffer1;
for (int i=0;i< nameEmp.length; i++){
randomAccessFile.writeInt(i+1);
buffer = new StringBuffer( nameEmp[i]);
buffer.setLength(10);
randomAccessFile.writeChars(buffer.toString());
buffer1 = new StringBuffer( addEmp[i]);
buffer1.setLength(100);
randomAccessFile.writeChars(buffer1.toString());
randomAccessFile.writeInt(saleEmp[i]);
randomAccessFile.writeInt(comEmp[i]);
}
randomAccessFile.close();
}
The Reader is
public static void main(String[] args) throws IOException {
File file = new File("C:\\Test\\employee.XML");
RandomAccessFile randomAccessFile = new RandomAccessFile(file, "rw");
int codeEmp, position = 0;
char nameEmp[] = new char[10];
char addEmp[] = new char [100];
int saleEmp , comEmp;
for(;;){
randomAccessFile.seek(position);
codeEmp = randomAccessFile.readInt();
for (int i = 0; i < nameEmp.length; i++) {
nameEmp[i] = randomAccessFile.readChar();
}
String nameEmpS= new String(nameEmp);
for (int i = 0; i < addEmp.length; i++) {
addEmp[i] = randomAccessFile.readChar();
}
String addEmpS= new String(addEmp);
saleEmp =randomAccessFile.readInt();
comEmp=randomAccessFile.readInt();
System.out.println("Cod Emp: " + codeEmp + ", nombre: " +nameEmpS+ ", dirección: "+addEmpS+
", sale: " + saleEmp+ ", comisión: " + comEmp );
position= position + 36;
if (randomAccessFile.getFilePointer()==file.length())break;
}
randomAccessFile.close();
}
The problem is that when I run the reader file, it's return many lines and only the first line is okay but the rest are wrong. How can I fix it?
Here is the console
Cod Emp: 1, nombre: Name A , dirección: Address A , sale: 2000, comisión: 400
Cod Emp: 7536672, nombre: A , dirección: Name B Ad, sale: 6553714, comisión: 6619251
Cod Emp: 0, nombre: , dirección: Ɛ Name B Address B , sale: 0, comisión: 0

You are assigning a "random" next read position here:
position= position + 36;
That makes no sense unless there is 36 bytes padding after every record. Comment out the line position= position + 36; and randomAccessFile.seek(position); because if you have the matched up each write with a read then the next seek position is moved correctly.
Also note:
writing a file called employee.XML which isn't XML format is very misleading for others.
You don't need to use RandomAccessFile here as all your writes are sequential.

Indexing for each word in the TextFile Content Using Java

I am trying to index each word in a text file Using java
Index means i am denoting indexing of words here..
This is my sample file https://pastebin.com/hxB8t56p
(the actual file I want to index is much larger)
This is the code I have tried so far
ArrayList<String> ar = new ArrayList<String>();
ArrayList<String> sen = new ArrayList<String>();
ArrayList<String> fin = new ArrayList<String>();
ArrayList<String> word = new ArrayList<String>();
String content = new String(Files.readAllBytes(Paths.get("D:\\folder\\poem.txt")), StandardCharsets.UTF_8);
String[] split = content.split("\\s"); // Split text file content
for(String b:split) {
ar.add(b); // added into the ar arraylist //ar contains every line of poem
}
FileInputStream fstream = null;
String answer = "";fstream=new FileInputStream("D:\\folder\\poemt.txt");
BufferedReader br = new BufferedReader(new InputStreamReader(fstream));
String strLine;
int count = 1;
int songnum = 0;
while((strLine=br.readLine())!=null) {
String text = strLine.replaceAll("[0-9]", ""); // Replace numbers from txt
String nums = strLine.split("(?=\\D)")[0]; // get digits from strLine
if (nums.matches(".*[0-9].*")) {
songnum = Integer.parseInt(nums); // Parse string to int
}
String regex = ".*\\d+.*";
boolean result = strLine.matches(regex);
if (result == true) { // check if strLine contain digit
count = 1;
}
answer = songnum + "." + count + "(" + text + ")";
count++;
sen.add(answer); // added songnum + line number and text to sen
}
for(int i = 0;i<sen.size();i++) { // loop to match and get word+poem number+line number
for (int j = 0; j < ar.size(); j++) {
if (sen.get(i).contains(ar.get(j))) {
if (!ar.get(j).isEmpty()) {
String x = ar.get(j) + " - " + sen.get(i);
x = x.replaceAll("\\(.*\\)", ""); // replace single line sentence
String[] sp = x.split("\\s+");
word.add(sp[0]); // each word in the poem is added to the word arraylist
fin.add(x); // word+poem number+line number
}
}
}
}
Set<String> listWithoutDuplicates = new LinkedHashSet<String>(fin); // Remove duplicates
fin.clear();fin.addAll(listWithoutDuplicates);
Locale lithuanian = new Locale("ta");
Collator lithuanianCollator = Collator.getInstance(lithuanian); // sort array
Collections.sort(fin,lithuanianCollator);
System.out.println(fin);
(change in blossom. - 0.2,1.2, & the - 0.1,1.2, & then - 0.1,1.2)

I will first copy the intended output for your pasted example, and then go over the code to find how to change it:
Poem.txt
0.And then the day came,
to remain blossom.
1.more painful
then the blossom.
Expected output
[blossom. - 0.2,1.2, came, - 0.1, day - 0.1, painful - 1.1, remain - 0.2, the - 0.1,1.2, then - 0.1,1.2, to - 0.2]
As #Pal Laden notes in comments, some words (the, and) are not being indexed. It is probable that stopwords are being ignored for indexing purposes.
Current output of code is
[blossom. - 0.2, blossom. - 1.2, came, - 0.1, day - 0.1, painful - 1.1, remain - 0.2, the - 0.1, the - 1.2, then - 0.1, then - 1.2, to - 0.2]
So, assuming you fix your stopwords, you are actually quite close. Your fin array contains word+poem number+line number, but it should contain word+*list* of poem number+line number. There are several ways to fix this. First, we will need to do stopword removal:
// build stopword-removal set "toIgnore"
String[] stopWords = new String[]{ "a", "the", "of", "more", /*others*/ };
Set<String> toIgnore = new HashSet<>();
for (String s: stopWords) toIgnore.add(s);
if ( ! toIgnore.contains(sp[0)) fin.add(x); // only process non-ignored words
// was: fin.add(x);
Now, lets fix the list problem. The easiest (but ugly) way is to fix "fin" at the very end:
List<String> fixed = new ArrayList<>();
String prevWord = "";
String prevLocs = "";
for (String s : fin) {
String[] parts = s.split(" - ");
if (parts[0].equals(prevWord)) {
prevLocs += "," + parts[1];
} else {
if (! prevWord.isEmpty()) fixed.add(prevWord + " - " + prevLocs);
prevWord = parts[0];
prevLocs = parts[1];
}
}
// last iteration
if (! prevWord.isEmpty()) fixed.add(prevWord + " - " + prevLocs);
System.out.println(fixed);
How to do it the right way (TM)
You code can be much improved. In particular, using flat ArrayLists for everything is not always the best idea. Maps are great for building indices:
// build stopwords
String[] stopWords = new String[]{ "and", "a", "the", "to", "of", "more", /*others*/ };
Set<String> toIgnore = new HashSet<>();
for (String s: stopWords) toIgnore.add(s);
// prepare always-sorted, quick-lookup set of terms
Collator lithuanianCollator = Collator.getInstance(new Locale("ta"));
Map<String, List<String>> terms = new TreeMap<>((o1, o2) -> lithuanianCollator.compare(o1, o2));
// read lines; if line starts with number, store separately
Pattern countPattern = Pattern.compile("([0-9]+)\\.(.*)");
String content = new String(Files.readAllBytes(Paths.get("/tmp/poem.txt")), StandardCharsets.UTF_8);
int poemCount = 0;
int lineCount = 1;
for (String line: content.split("[\n\r]+")) {
line = line.toLowerCase().trim(); // remove spaces on both sides
// update locations
Matcher m = countPattern.matcher(line);
if (m.matches()) {
poemCount = Integer.parseInt(m.group(1));
lineCount = 1;
line = m.group(2); // ignore number for word-finding purposes
} else {
lineCount ++;
}
// read words in line, with locations already taken care of
for (String word: line.split(" ")) {
if ( ! toIgnore.contains(word)) {
if ( ! terms.containsKey(word)) {
terms.put(word, new ArrayList<>());
}
terms.get(word).add(poemCount + "." + lineCount);
}
}
}
// output formatting to match that of your code
List<String> output = new ArrayList<>();
for (Map.Entry<String, List<String>> e: terms.entrySet()) {
output.add(e.getKey() + " - " + String.join(",", e.getValue()));
}
System.out.println(output);
Which gives me [blossom. - 0.2,1.2, came, - 0.1, day - 0.1, painful - 1.1, remain - 0.2, to - 0.2]. I have not fixed the list of stopwords to get a perfect match, but that should be easy to do.

Weird console output after temporary redirection of System.out

Under normal conditions the following code:
String[] outputStrings = {" Initial values: a = 1, b = 2 ", "Swapped values: a = 2, b = 1", ""};
System.out.println("array length: " + outputStrings.length);
int i = 0;
for (String line: outputStrings) {
String str = Integer.toString(i) + " : |" + line + "| ";
System.out.println(str);
//System.out.flush();
i++;
}
Has the following output:
array length: 3
0 : | Initial values: a = 1, b = 2 |
1 : |Swapped values: a = 2, b = 1|
2 : ||
However, the following code:
CommandLineTestScaffolding scaffolding;
scaffolding = new CommandLineTestScaffolding(ExchangeCL::main);
String[] inputStrings = {"1", "2"}; // string literals with integer numbers
String[] outputStrings = scaffolding.run(inputStrings);
scaffolding = null; //no longer necessary
System.out.println("array length: " + outputStrings.length);
int i = 0;
for (String line: outputStrings) {
String str = Integer.toString(i) + " : |" + line + "| ";
System.out.println(str);
//System.out.flush();
i++;
}
Has the following strange output:
array length: 1
0 : | Initial values: a = 1, b = 2
Swapped values: a = 2, b = 1
|
For information, the CommandLineTestScaffolding is a simple contraption to temporary redirect System.out to fetch command line output to an array of strings:
public class CommandLineTestScaffolding {
private Consumer<String[]> theMethod; //Place to store main method generating text output
public CommandLineTestScaffolding(Consumer<String[]> method) {
theMethod = method;
}
public String[] run(String[] args) {
// Create a stream to hold the output
ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
PrintStream printStream = new PrintStream(outputStream);
// A variable to temporarily hold System.out stream
PrintStream oldOutputStream = null;
// Critical section. System.out must be restored to its original value
try {
System.out.flush(); // Clear buffer;
// IMPORTANT: Save the old System.out!
oldOutputStream = System.out;
// Use new wrapped byte array stream
System.setOut(printStream);
theMethod.accept(args); //Run the method. fill the stream
printStream.flush(); // Clear buffer;
}
finally {
// Put things back
System.setOut(oldOutputStream);
}
String[] output = outputStream.toString().split("/n"); //split into lines with regex
printStream = null;
outputStream = null;
return output;
}
}
What leads to such strange behaviour?

outputStrings has just one element, and it is "0 : | Initial values: a = 1, b = 2
Swapped values: a = 2, b = 1
| "
So, it is not strange behaviour.
Your CommandLineTestScaffolding does not do the job ypu expect.
However, i did not understand what you need? You need exact same output with 1?

Creating an ArrayList from data in a text file

I am trying to write a program that uses two classes to find the total $ amount from a text file of retail transactions. The first class must read the file, and the second class must perform the calculations. The problem I am having is that in the first class, the ArrayList only seems to get the price of the last item in the file. Here is the input (which is in a text file):
$69.99 3 Shoes
$79.99 1 Pants
$17.99 1 Belt
And here is my first class:
class ReadInputFile {
static ArrayList<Double> priceArray = new ArrayList<>();
static ArrayList<Double> quantityArray = new ArrayList<>();
static String priceSubstring = new String();
static String quantitySubstring = new String();
public void gatherData () {
String s = "C:\\filepath";
try {
FileReader inputFile = new FileReader(s);
BufferedReader bufferReader = new BufferedReader(inputFile);
String line;
String substring = " ";
while ((line = bufferReader.readLine()) != null)
substring = line.substring(1, line.lastIndexOf(" ") + 1);
priceSubstring = substring.substring(0,substring.indexOf(" "));
quantitySubstring = substring.substring(substring.indexOf(" ") + 1 , substring.lastIndexOf(" ") );
double price = Double.parseDouble(priceSubstring);
double quantity = Double.parseDouble(quantitySubstring);
priceArray.add(price);
quantityArray.add(quantity);
System.out.println(priceArray);
} catch (IOException e) {
e.printStackTrace();
}
}
The output and value of priceArray is [17.99], but the desired output is [69.99,79.99,17.99].
Not sure where the problem is, but thanks in advance for any help!

Basically what you have is:
while ((line = bufferReader.readLine()) != null) {
substring = line.substring(1, line.lastIndexOf(" ") + 1);
}
priceSubstring = substring.substring(0,substring.indexOf(" "));
quantitySubstring = substring.substring(substring.indexOf(" ") + 1 , substring.lastIndexOf(" ") );
double price = Double.parseDouble(priceSubstring);
double quantity = Double.parseDouble(quantitySubstring);
priceArray.add(price);
quantityArray.add(quantity);
System.out.println(priceArray);
So all you are doing is creating a substring of the line you just read, then reading the next line, so basically, only the substring of the last will get processed by the remaining code.
Wrap the code in {...} which you want to be executed on each iteration of the loop
For example...
while ((line = bufferReader.readLine()) != null) {
substring = line.substring(1, line.lastIndexOf(" ") + 1);
priceSubstring = substring.substring(0,substring.indexOf(" "));
quantitySubstring = substring.substring(substring.indexOf(" ") + 1 , substring.lastIndexOf(" ") );
double price = Double.parseDouble(priceSubstring);
double quantity = Double.parseDouble(quantitySubstring);
priceArray.add(price);
quantityArray.add(quantity);
System.out.println(priceArray);
}
This will execute all the code within the {...} block for each line of the file

End line StringBuilder in RandomAccessFile

I'm trying use the class RandomAccessFile, but I have a problem with the Strings.
This is the first part. Write in a File:
public static void main(String[] args) throws IOException {
File file = new File("/home/pep/java/randomFile.dat");
RandomAccessFile fitxerAleatori = new RandomAccessFile(file, "rw");
String[] surnames = { "SMITH",
"LOMU" };
int[] dep = { 10,
20 };
Double[] salary = { 1200.50,
1200.50 };
StringBuilder buffer = null;
int n = surnames.length;
for (int i = 0; i<n; i++){
randomFile.writeInt(i+1); //ID
buffer = new StringBuilder(surnames[i]);
buffer.setLength(10); //10 characters
randomFile.writeChars(buffer.toString());
randomFile.writeInt(dep[i]);
randomFile.writeDouble(salary[i]);
}
randomFile.close();
}
In the second part, I try read this file:
File file = new File("/home/pep/java/randomFile.dat");
RandomAccessFile randomFile = new RandomAccessFile(file, "r");
char[] surname = new char[10];
char aux;
int id, dep, pos;
Double salary;
pos = 0;
for (;;) {
randomFile.seek(pos);
id = randomFile.readInt();
for (int i = 0; i < surname.length; i++) {
aux = randomFile.readChar();
surname[i] = aux;
}
String surnameStr = new String(surname); //HERE IS THE PROBLEM!!
dep = randomFile.readInt();
salary = randomFile.readDouble();
System.out.println("ID: " + id + ", Surname: " + surnameStr + ", Departament: " + dep + ", Salary: " + salary);
pos = pos + 36; // 4 + 20 + 4 + 8
if (randomFile.getFilePointer() == randomFile.length())
break;
}
randomFile.close();
}
Well, when I hope read:
ID: 1, Surname: SMITH, Dep: 10, Salary: 1200.50
I recived:
ID: 1, Surname: SMITH
It's like in the surname there is a end of line, because if I don't display the surname, the other info is correct.
Thank you!

Where does cognom come from? [Edit: OK, I found it. It's Catalan for surname. And now the typo coming from departamento is also clear. :-]
What do you get if you insert System.out.println( Arrays.toString( surname )) before the problem line? I assume it's something like [S, M, I, T, H, [], [], [], [], []] (in Eclipse's Console view). Where [] stands for a square, i.e. a non-printable character.
What do you get if you insert System.out.println( (int) surname[5] )? I assume it's 0. And I assume this 0 value is causing the problem.
What do you get if you use a surname that's exactly 10 characters long?
Hint 1: There's a typo in Departament.
Hint 2: Give System.out.printf(...) a chance in favour of println(...).
Hint 3: The if in your solution can be shortened to the more elegant:
cognom[i] = aux != 0 ? aux : ' ';

The problem was in the char array. I change de loop for that read the chars:
for (int i = 0; i < surname.length; i++) {
aux = randomFile.readChar();
surname[i] = aux != 0 ? aux : ' ';
}

Creating a StringBuffer and setting its length to ten will cause nulls to be written for strings shorter than ten characters, and that in turn will cause a decoding problem when you read. It would be much better to create a String, pad it with spaces to ten chars, write it, then trim() the resulting String when you read it.