We Keep Coding

Create a shortcut/macro that runs a predefined chunk of code?

Sorry if this question has been asked before, but I'm new to coding and I can't find an answer online because I don't know the theory well enough to know how to describe what I'm looking for.
Basically, I want to know if theres a way I can initialize a variable/macro that I can tie to this long try statement, so instead of writing THIS every time I want to read my file
System.out.println("filler");
System.out.println("filler");
try {
FileReader reader = new FileReader("MyFile.txt");
BufferedReader bufferedReader = new BufferedReader(reader);
String line;
while ((line = bufferedReader.readLine()) != null) {
System.out.println(line);
}
reader.close();
} catch (IOException e) {
e.printStackTrace();
}
System.out.println("filler");
System.out.println("filler");
I can just write something like..
System.out.println("filler");
System.out.println("filler");
Read1
System.out.println("filler");
System.out.println("filler");

As #king_nak suggests, use a method.
public void readFile(String path) {
try {
FileReader reader = new FileReader(path);
BufferedReader bufferedReader = new BufferedReader(reader);
String line;
while ((line = bufferedReader.readLine()) != null) {
System.out.println(line);
}
reader.close();
} catch (IOException e) {
e.printStackTrace();
}
}
And then you can do what you wanted:
System.out.println("filler");
readFile("MyFile.txt") // call the method
System.out.println("filler");

In Java, MACROS are called constants instead, and are initialised with the final keyword.
For having a String constant for example:
final String str = "Hello World!";
What you need here, is a good ol' fashioned Java method.
You need to declare it outside your main method, in a class of your choosing. What the following method will do, is that it will read a file and add each line of the file to a list (an ArrayList more specifically).
Each element of the ArrayList is one line of text, read from the file.
Note: This method is quite advanced, since it utilises streams to achieve what was described above. If you use this, then please spend some time to understand it first! Otherwise, I would suggest you don't use this as a beginner. (You can read the documentation for for Reading, Writing and Creating files).
public ArrayList<String> readLines (String filename){
ArrayList<String> lines = null;
// Get lines of text from file as a stream.
try (Stream<String> stream = Files.lines(Paths.get(filename))){
// convert stream to a List-type object
lines = (ArrayList<String>)stream.collect(Collectors.toList());
}
catch (IOException ioe){
System.out.println("Could not read lines of text from the file..");
ioe.printStackTrace();
}
return lines;
}
Then you can use the method like so:
ArrayList<String> lines = null; //Initialise an ArrayList to store lines of text.
System.out.println("filler");
lines = readLines("/path/myFile.txt");
System.out.println(lines.get(0)); //Print the first line of text from list
System.out.println("filler");
lines = readLines("/path/myOtherFile.txt");
for( String str : lines )
System.out.println(str); //Will print every line of text in list
Here is the link for the documentation for java.nio.Files.

Creating an inverted index with limited memory in java

Im curious on how create an Inverted Index on data that doesn't fit into memory. So right now I'm reading a file directory and indexing the files based on the contents inside the file, I am using a HashMap to store the index. The code below is a snippet from a function I use and I call the function on an entire directory. What do I do if this directory was just massive and the HashMap can't fit all the entries. Yes, This does sound like premature optimization. Im just having fun. I don't want to use Lucene so don't even mention it because I'm tired as to seeing that as the majority answer to "Index" stuff. This HashMap is my only constraint everything else is stored in files to easily reference stuff later on.
Im just curious how I can do this since it stores it in the map like so
keyword -> file1,file2,file3,etc..(locations)
keyword2 -> file9,file11,file13,etc..(locations)
My thoughts were to create a file which would some how be able to update itself to be like the format above but I feel thats not efficient.
Code Snippet
br = new BufferedReader(new FileReader(file));
while ((line = br.readLine()) != null) {
for (String _word : line.split("\\W+")) {
word = _word.toLowerCase();
if (!ignore_words.contains(word)) {
fileLocations = index.get(word);
if (fileLocations == null) {
fileLocations = new LinkedList<Long>();
index.put(word, fileLocations);
}
fileLocations.add(file_offset);
}
}
}
br.close();
Update:
So I managed to come up with something, but performance wise I feel this is slow, especially if there was a large amount of data. I basically created a file that would just have to word and its offset on each line the word appeared.Lets name it index.txt.
It had the format of like so
word1:offset
word2:offset
word1:offset <-encountered again.
word3:offset
etc...
I then created multiple files for each word and appended the offset to that file each time it was encountered in the index.txt file.
So basically the format of the word files are like so
word1.txt -- Format
word1:offset1:offset2:offset3:offset4...and so on
each time word1 is encountered in the index.txt file it would append it to the word1.txt file and add to end.
Then finally, I go through all the word files I created and overwrite the index.txt file with the final output in the index file looking like so
word1:offset1:offset2:offset3:offset4:...
word2:offset9:offset11:offset13:offset14:...
etc..
Then to finish it up, I delete all the word files.
The nasty code snippet for this is below, its a fair amount.
public void createIndex(String word, long file_offset)
{
PrintWriter writer;
try {
writer = new PrintWriter(new FileWriter(this.file,true));
writer.write(word + ":" + file_offset + "\n");
writer.close();
}
catch (IOException ioe)
{
ioe.printStackTrace();
}
}
public void mergeFiles()
{
String line;
String wordLine;
String[] contents;
String[] wordContents;
BufferedReader reader;
BufferedReader mergeReader;
PrintWriter writer;
PrintWriter mergeWriter;
try {
reader = new BufferedReader(new FileReader(this.file));
while((line = reader.readLine()) != null)
{
contents = line.split(":");
writer = new PrintWriter(new FileWriter(
new File(contents[0] + ".txt"),true));
if(this.words.get(contents[0]) == null)
{
this.words.put(contents[0], contents[0]);
writer.write(contents[0] + ":");
}
writer.write(contents[1] + ":");
writer.close();
}
//This could be put in its own method below.
mergeWriter = new PrintWriter(new FileWriter(this.file));
for(String word : this.words.keySet())
{
mergeReader = new BufferedReader(
new FileReader(new File(word + ".txt")));
while((wordLine = mergeReader.readLine()) != null)
{
mergeWriter.write(wordLine + "\n");
}
}
mergeWriter.close();
deleteFiles();
}
catch(IOException ioe)
{
ioe.printStackTrace();
}
}
public void deleteFiles()
{
File toDelete;
for(String word : this.words.keySet())
{
toDelete = new File(word + ".txt");
if(toDelete.exists())
{
toDelete.delete();
}
}
}

jTextArea saves only first line of text in text file using BufferedReader?

I am trying to save the multiple line output in a text file from my jTextArea(named as "outputarea" in a code) to my desired path, Everything is OK but the file being saved do not contain the whole output, but only first line oof text. I am using "\n" to break the line in jtextarea while giving multiple line output, does that make any difference or any other problem in this code, This code is just the code on saveAs button, output is coming from another methods I've created. Thanks in Advance!
private void saveAs() {
FileDialog fd = new FileDialog(home.this, "Save", FileDialog.SAVE);
fd.show();
if(fd.getFile()!=null)
{
fn=fd.getFile();
dir=fd.getDirectory();
filename = dir + fn +".txt";
setTitle(filename);
try
{
DataOutputStream d=new DataOutputStream(new FileOutputStream(filename));
holdText = outputarea.getText();
BufferedReader br = new BufferedReader(new StringReader(holdText));
while((holdText = br.readLine())!=null)
{
d.writeBytes(holdText+"\r\n");
d.close();
}
}
catch (Exception e)
{
System.out.println("File not found");
}
outputarea.requestFocus();
save(filename);
}
}

You should put the d.close(); after the completion of while loop, because just after writing the first line in the file using DataOutputStream, you are closing it and you don't let it to fulfill the whole job.
You can see even an error is wrote in your console:
File not found
This is not because it doesn't find your file, it's because in the iterations after the first, it tries to write into a closed stream. So only the first line is wrote then. So change you code like this:
while ((holdText = br.readLine()) != null) {
d.writeBytes(holdText + "\r\n");
}
d.close();
Also I can advise to use a PrintWriter instead of DataOutputStream. Then you can easily change the writeBytes into println method. In this way you don't need to append \r\n manually to each line you write.
Another good hint is to use a try-with-resource (in case you use java 7 or later) or at least a finally block to close your streams either way:
String holdText = outputarea.getText();
try (PrintWriter w = new PrintWriter(new File(filename));
BufferedReader br = new BufferedReader(new StringReader(holdText))) {
while ((holdText = br.readLine()) != null) {
w.println(holdText);
}
} catch (Exception e) {
System.out.println("File not found");
}
Good Luck.

Words read from file are null

I am attempting to read some words off of the file "words.txt", then use them in other classes of my program when it runs. This is what I have found on the internet, and it doesn't seem to be working properly.
public static List<String> wordsList;
public static void refreshWords(){
String fileName = "words.txt";
String line = null;
try {
FileReader fileReader =
new FileReader(fileName);
BufferedReader bufferedReader =
new BufferedReader(fileReader);
while((line = bufferedReader.readLine()) != null) {
for(String tempWord : line.split(" ")){
wordsList.add(tempWord);
}
}
bufferedReader.close();
}
catch(FileNotFoundException ex) {
System.out.println(
"Unable to open file '" +
fileName + "'");
}
catch(IOException ex) {
System.out.println(
"Error reading file '"
+ fileName + "'");
}
}
public static List<String> getListOfWords(){
return wordsList;
}
I, from the message displayed before the program even runs, which cancels the entire thing, can determine that the error is sparking from adding tempWord to wordsList. I would assume that tempWord is null, but I can't seem to find a reason why it is.
All that I have in the file are a bunch of random words that I thought of off the top of my head, formatted like the following:
this game turtle forest soccer football ball java list annoyed

What you are using there is the old way of doing it (before Java 7).
With Java 7 / 8, reading a file is much easier. So rather than looking for bugs, I'd rewrite this using the new API:
List<String> lines = Files.readAllLines(yourFile.toPath(), StandardCharsets.UTF_8);
See Files.readAllLines(Path, Charset)
Also, in your question, you are splitting lines into words. That's highly unusual, word lists are almost always one word per line.

Restart File writing after certain number of lines

I'm working in Android trying to write some lines into a file. After a certain amount of lines, say 100, I want the file to delete the first line, and then append a line to the end. So basically, I want to keep writing to the file but keep the limit at 100 lines. I have been reading and found the files in java aren't to friendly with what I'm trying to do. I haven't found anything here either http://docs.oracle.com/javase/tutorial/essential/io/file.html
Is there a better way of keeping a file to the limit of 100 lines, and deleting the oldest lines when adding the new lines after that?
More specifically, I want a textView to display the 100 most recent events that a service has sent.
As of now, I have this method to display my STORETEXT file,
public void readFileInEditor() {
try {
InputStream in = openFileInput(STORETEXT);
if (in != null) {
InputStreamReader tmp = new InputStreamReader(in);
BufferedReader reader = new BufferedReader(tmp);
String str;
StringBuilder buf = new StringBuilder();
while ((str = reader.readLine()) != null) {
buf.append(str + "\n");
}
in.close();
writelog.setText(buf.toString());
}
} catch (java.io.FileNotFoundException e) {
// that's OK, we probably haven't created it yet
} catch (Throwable t) {
Toast.makeText(this, "Exception: " + t.toString(),
Toast.LENGTH_LONG).show();
}
}
and I write to the file like this...
OutputStreamWriter out = new OutputStreamWriter(openFileOutput(
STORETEXT, MODE_APPEND));
out.write("Some User Activity");
out.write("\n");
out.close();
I want to modify my code to only write the 100 most recent activities, and then set that to my textView. Thanks for any help.