I have two txt files with a specific structure. There should be som empty rows and rows with some data. Something like this:
#RELATION Table
#RECORD 1
ID '5'
SOMETHING '10'
The point is, there can be 10 'empty' rows in one file and there can none in second and if the data equals, it should not matter. Any ideas how to effectively do it with big files ?
BufferedReader should be used to read from file, supplying a FileReader to its constructor:
https://docs.oracle.com/javase/7/docs/api/java/io/BufferedReader.html
So you will have two of them, one for each file.
Have an "infinite loop" such as: while(true){}
Within this container loop, you should have two internal loops, one for each file.
In each internal loop, using the method readLine() you should advance the cursor to the next line.
declare this outside of the container loop:
String lineFromFileA, lineFromFileB;
and then:
while((lineFromFileA = bufferedReaderA.readLine()) != null){
if(!lineFromFileA.isEmpty())
break;
}
do the same with lineFromLineB.
an alternative to the above loop is:
while((lineFromFileA = bufferedReaderA.readLine()) != null && lineFromFileA.isEmpty());
After the two internal loops, both lineFromFileA and lineFromFileB are either null or has a value that is not an empty String.
If both are null, then you are done with the comparison, the two files are equal and you may return true from the function.
If one contains null and the other does not, return false. The files are different.
If both are not null, then check the equals() method if the two Strings are identical, if they are not, return false from the function. If they are equal, do nothing, the next iteration of the container loop will handle the next line.
Related
I have a code that compares data but that data contains null values not blank spaces ("") they may/may not be same i guess but I tried comparing repetitive NULL values like
for(int i=0;i<length;i++)
{
String data=sample_data.getData();// contains about
1000 null rows
if(data.equals(null) || data.equals("") || data== null
||data.isEmpty())
System.out.print("No Data");
}
I could have used .contains but that wont work because it is in the loop.
None of the method makes it print the output as No Data I have tried using try catch as well because in order to make sure if theres any error found and was correct at the same time isEmpty() and .equals(null) were somewhere or the other throwing the exception as NULL but even after removing and simply using ==Null realizing the fact that data is itself null and comparing like null.equals wont work but in case of == I found that the error exception got changed to value as 1 thereafter the same error and I wasnt able to recognize this.
Its the sample here which I am showing I cant post the exact but the above makes quite clear. Is there any other way I could treat these NULL values.
Note: I dont want to use a loop to iterate data as well and each time comparing NULL values because already theres an outer loop for large set of values dont go by the sample code.
Restoring windows to factory settings will restore windows (as its name suggests); it won't spoil anything.
In this
String data=sample_data.getData();// contains about 1000 null rows
if(data.equals(null) || data.equals("") || data== null
you are apparently concerned that data may be null.
If indeed it is null, then the very first clause in your if statement will throw a null pointer exception... because you can't call the equals method on a null reference.
You want
if (data == null || data.isEmpty())
and that covers all the cases of nothing, except possibly the case where data is "some number of space characters", but I'll leave that for you.
Ok, I have this program that is supposed to store information about CDs that are available in txt file. The file stores the data in format 'artist[tab]album' on the same line. What I want to do, is to have user input search query, and the program return if the CD is in the database. So let's say we have Green Day[tab]American Idiot in .txt file on some line, and when users types in Green, the programs checks that file and returns true. But my problem is, my current algorithm requires the string to completely match, instead of partial. So the users needs to type Green Day[tab]American Idiot to get true on the query. How to fix it? Thanks. I am sure it is something I don't see as beginner.
This is the part of the program that manages the search in the array Artists, that contains all the data currently stored in the .txt file
for (String e : artists){
if(Arrays.asList(e).contains(search)){
contains=true;
}
Why are you creating a list? You should use artist.contains(search) (yes, try to choose more relevant variable names). Also make sure you don't have null elements in the array or search is not null etc, but you can do something like:
for(String artist : artists) {
if(artist.toLowerCase().contains(search.toLowerCase()) {
contains = true;
// break; <- you may want to break here
}
}
You may want to toLowerCase() both of them for case-insensitive search.
I might just be doing something stupid here but I'm trying to write a program that will take all the text from an xml file, put it in an arraylist as strings, then find certain recurring strings and count them. It basically works, but for some reason it won't go through the entire xml file. It's a pretty large file with over 15000 lines (ideally I'd like it to be able to hand any amount of lines though). I did a test to output everything it was putting in the arraylist to a .txt file and eventually the last line simply says "no", and there's still much more text/lines to go through.
This is the code I'm using to make the arraylist (lines is the amount of lines in the file):
// make array of strings
for (int i=0; i<lines; i++) {
strList.add(fin2.next());
}
fin2.close();
Then I'm searching for the desired strings with:
// find strings
for (String string : strList) {
if(string.matches(identifier)){
count++;
}
}
System.out.println(count);
fout.println(count);
It basically works (the printwriter and scanners work, line count works, etc) except the arraylist won't take all the text from the .xml file, so of course the count at the end is inaccurate. Is arraylist not the best solution for this problem?
This is a BAD practice to do. Each time you put a string into an ArrayList and keep it there, you're going to have an increase in memory usage. The bigger the file, the more memory is used up to the point where you're wondering why your application is using 75% of your memory.
You don't need to store the lines into an ArrayList in order to see if they match. You can simply just read the line and compare it to whatever text you're comparing it to.
Here would be your code modified:
String nextString = "";
while (fin2.hasNext()) {
nextString = fin2.next();
if (nextString.matches(identifier) || nextString.matches(identifier2)) {
count++;
}
}
fin2.close();
System.out.pritnln(count);
Eliminates looping through everything twice, saves you a ton of memory, and gives you accurate results. Also I'm not sure if you're meaning to read the entire line, or you have some sort of token. If you want to read the entire line, change hasNext to hasNextLine and next to nextLine
Edit: Modified the code to show what it would look like looking for multiple strings.
Have you tried to use map, like HashMap. Since Your goal is to find the occurrence of word from a xml, hashmap will make your like easier.
The problem is not with your ArrayList but with your for loop. What's happening is that you're using the number of lines in your file as your sentinel value, but rather than incrementing i by 1 every line, you are doing it every word. Therefore, not all the words are added to your ArrayList because your loop terminates earlier than expected. Hope this helps!
EDIT: I don't know what object you are using right now to collect the contents of this xml file, but I would suggest using Scanner instead (passing the File as a parameter in the constructor) and replacing the current for loop with a while loop that uses while (nameOfScanner.hasNextLine())
I have a file Hier.csv which looks like this (thousands of lines):
value;nettingNodeData;ADM59505_10851487;CVAEngine;ADM;;USD;0.4;35661;BDR;NA;ICE;;RDC;MAS35661_10851487;CVAEngine;MA;10851487;RDC
I have another one, Prices.csv, which looks like this :
value;nettingNodePrices;ADM68834_22035364;CVAEngine;CVA with FTD;EUR;1468.91334249291905;DVA with FTD;EUR;5365.59742483701497
I have to make sure that both files have the same number of lines and the same ids (the third value of each lines), and it's a known fact that the set of ids from Hier.csv is larger and contains the set of ids from Prices.csv, ie. some ids that are in Hier.csv are not in Prices.csv.
Also, there are no duplicates in either file.
So far, I have tried the following, but it's taking ages, and not working (I can do it faster with my little hands and Excel, but that's not what I want).
Here is my program in pseudo code, as I don't have access to my code right now, I will edit this question as soon as I can :
for each line of Hier.csv
for each line of Prices.csv
if prices.line doesn't contain the 3rd value of hier.line
store that value in a list
end
end
end
Process p;
for each value in the list
// remove the line containing that value from Hier.csv
String[] command1 = {"sed", "'/^.*" + value + ".*$/d'", "Hier.csv", ">", "tmp.csv"};
Process p = Runtime.getRuntime().exec(command1)
end
String[] command2 = {"mv", "tmp.csv" "Hier.csv"};
Process p = Runtime.getRuntime().exec(command2)
Is there a better way than that double loop ?
Why does'nt the last part (exec(command)) work ?
And lastly, which is more efficient when reading csv files : BufferedReader or Scanner ?
You can use merge or hashtable.
Merge:
sort both files and merge together
Hashtable:
load smaller file (ids) to hashtable, loop through bigger file and test existence against hashtable
I'm parsing a CSV using Processing's Table interface, but some rows are missing some data. I want to pull all the data available into my table, but I'm not sure how to handle the missing data--I keep getting NullPointerException when I loop over the table with dataTable.getInt on the missing values.
I don't have a background in statically typed languages, so I've no idea how to conditionally assign this data short of putting a separate try/catch around each assignment. Surely there's a better way?
Before calling dataTable.getInt method check if dataTable is not null like
if(dataTable != null) {
int my_nt = dataTable.getInt
}
//else skip since it is empty
Since your're using getInt--you should perform a regex search/replace ,<not numeric>, with ,<some int>,. In your case it may be as simple as replacing ,, with ,0,
Also, as Hassan suggests, double check that dataTable is not null.
Ok, so I figured out a way to do this:
First, call dataTable.makeNullEmpty(), which turns all the null values into empty strings.
Then, you can use a pattern like this:
String total_value = dataTable.getString(i, 4);
if(total_value.length() > 0) s.total_value = parseInt(total_value);
and you get assignment only if an int is there to be parsed.