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Assigning a file name to a variable in java [closed]

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I want to simply assign the file name "database.txt" to a string type variable say "fname".
What is the code for it for java.
I want to use relative file destinations.

try something like this :
File file = new File("your/path");
String str = file.getName();

reading next lines from a file after particular pattern [closed]

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I have to read a file if some pattern occurs that file i have to read next lines of the text file in java
while (sc1.hasNextLine()){
String a = sc1.nextLine();
String b = sc1.nextLine();
if(a.contains("pattern")){
//read next lines
}
}

To simply read the file to find the line you want, just use a loop until you reach the end or the pattern your want like this :
while(sc1.hastNextLine() && !sc.nextLine().contains("pattern")){
//skip
}
then you just have to check if there is still a line to read
if (sc1.hastNextLine()){
//read the line
}

Call a C program in Java [closed]

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I know there is already some posts about this but none of them answered my question.
Here's the situation, I have program written in C but I developped my GUI in java. So what I need to do, is calling my C program when I click on a button or a combobox.
In order to do that, is it possible to just compile the C program and then call it in my java interface ? (and if it is possible, how do I do that ?).
Or do I have to use JNI ? (I've read some posts about it but it seemed quite complicated to learn it for just one project).

To have maximum interoperability you should use JNI, but as a simple approach just compile C code and call C executable from JAVA with Runtime.getRuntime().exec().
if you are under UNIX to read response you could do something like this:
String line;
Process p = Runtime.getRuntime().exec( "/path/to/C/executable" );
BufferedReader in = new BufferedReader(new InputStreamReader(p.getInputStream()));
while ((line = in.readLine()) != null) {
System.out.println(line);
}
in.close();

Write java array to file.txt in one line [closed]

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What should I change in my code to write my array into text file in a single line instead of a different line per vale of the array?
PrintWriter zapis = new PrintWriter("wyniki.txt");
for (int g=1; g<801; g++)
{
zapis.println(g+":"+wynik[g]+" ");
}
zapis.close();

As the documentation states, println "Prints a String and then terminates the line."
If you don't want to terminate the line, use print instead.

Change the line inside for loop like this :
zapis.print(g+":"+wynik[g]+" ");

Java: looking for chars in a binary file [closed]

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I need to look into a binary file.
I need to parse it in order to read some chars that the file contains.
Please any hint of how could I do it?
Thanks!
To be more specific I am looking for a particular sequence of chars in the file.

I suggest using a BufferedReader:
BufferedReader br = new BufferedReader(new FileReader(file));
String line;
int index;
while(line = br.readLine() != null) {
index = line.indexOf(string);
if (index != -1) break;
//Assuming your file has some sort of key/value data
}