How to count number of occurrences of pattern within a string?

Some Assistance with Java IO?

• After many attempts, I still can't get this correctly, any advice/help/corrections would be appreciated. Instructions: You will read one file to search for a given word and store a file with the search result. In addition, you are asked to print out the search result on the screen. For example, your program will take the following inputs from the keyboard. Enter a filename to read from: input.txt Enter a filename to write to: output.txt Enter a word to search: value Then, the following lines will be printed on the screen. Also, the same contents will be written to the output file (i.e., “output.txt” in this example). For your information, if m lines in the input file contain the search word, the screen and the input file will have m+2 lines. Therefore, just in case there is no line that contains the search word, only the last two lines will be printed on the screen and the output file. Line 1 contains the word “value” – number of occurrences = 1 Line 3 contains the word “value” – number of occurrences = 1 Line 6 contains the word “value” – number of occurrences = 3 … File “input.txt” contains 100 lines Number of occurrences of “value” = 33 (Requirement 1) The case in the search word and the file will be ignored. For example, the words will be considered identical: “VALUE”, “value”, “Value”, and so on. (Requirement 2) The search word can be either a substring or a whole string of an individual word in the input file. MY PROGRAM BELOW: public class LucVincentSearchWord { // This method will read an input file line by line, then search for occurrences of the searchTerm public void searchWordInFile(File input, File output, String searchTerm) { System.out.println("What file to read from? "); System.out.println("What filename to write to? "); System.out.println("Enter a word to search: "); } public static void main(String[]args) throws IOException { // Create a Scanner object for keyboard input. Scanner keyboard = new Scanner(System.in); // Create a line counter variable int count = 0; Scanner input = new Scanner(); Scanner kbd = new Scanner(System.in); String line; String word; String searchTerm; String filename; // Get the filename. System.out.print("Enter the filename: "); filename = keyboard.nextLine(); // Open the input file PrintWriter outputFile = new PrintWriter(filename); // Open the output file System.out.println("What word you want to search for? "); word = kbd.nextLine(); while (input.hasNext()) { line = input.nextLine(); if (line.indexOf(word) >= 0) { System.out.println(line); count++; } } System.out.println(word + " occurs on " + count + " line(s) "); input.close(); // Close the input file // Close the output file } // This would contain your search and count logic and would return the count private int getWordOccurrenceCount(String inputLine, String searchTerm) { return ; } // Use whatever techniques you want to find occurrences of the search term and report a count back }

• Answer:

  Here is the String API: http://docs.oracle.com/javase/1.5.0/docs/api/java/lang/String.html Take a look at the String.indexOf(String,int) method. That's the one you want to use. You'll have to put it together with a bit of extra program logic, but I think you can figure that part out on your own.