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I'm writing a method to search a text file of words in list form, for a word that is entered by the user but by program will return a positive result if one letter is at all is found e.g, if i search "f" it will return that there's is a word "F" in the dictionary when there isn't 

public static void Option3Method(String dictionary) throws IOException { Scanner scan = new Scanner(new File("wordlist.txt")); String s; String words[] = new String[500]; String word = JOptionPane.showInputDialog("Enter a word to search for"); while (scan.hasNextLine()) { s = scan.nextLine(); int indexfound = s.indexOf(word); if (indexfound > -1) { JOptionPane.showMessageDialog(null, "Word was found"); } else if (indexfound < -1) { JOptionPane.showMessageDialog(null, "Word was not found"); } } }
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if (indexfound>-1) { JOptionPane.showMessageDialog(null, "Word was found"); } else if (indexfound<-1) { JOptionPane.showMessageDialog(null, "Word was not found");} }

The problem with this code is that indexFound can be equal to -1, but never less than -1. Change the < operator for a == operator.

An alternative

This is quite an obscure method for checking if a String exists in another String. It's much more appropriate to use the matches method in the String object. Here is the documentation.

Example

Something like:

String phrase = "Chris"; String str = "Chris is the best"; // Load some test values. if(str.matches(".*" + phrase + ".*")) { // If str is [something] then the value inside phrase, then [something],true. }
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Instead of String#indexOf use String#matches method like this:

boolean matched = s.matches("\\b" + word + "\\b");

This will make sure user entered word is found in the the line with word boundaries.

btw its not clear why did you declare words a String array with 500 elements, you are not using it anywhere.

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You say letter, you say word, what do you search exactly?

I you search word, you have to search a word inside word boundaries: regex java.util.regex.Pattern \b as shown by anubhava.

You may replace } else if (indexfound < -1) { by } else { because java.lang.indexOf() return -1 when not found >-1 otherwise, < -1 does never occurs.

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Your "else if" statement should read

} else if (indexfound == -1){

Because the indexOf method returns exactly -1 if it doesn't find the substring.

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I find a couple of things confusing in your code.

  • It looks like your outputting the result once per word instead of once for the entire file.
  • When you have a dictionary you normally have only one word per line so it will either match or not match. It looks like you (and most other answers) tries to find the word inside a longer String which probably isn't what you want. If you search for 'ee' you don't want to find it in 'beer', right?

So, assuming that the dictionary is one valid word per line and that you wan't to find the word anywhere in the entire dictionary this simple code will do the trick.

import java.io.File; import java.io.FileNotFoundException; import java.util.Scanner; public class Main { public static void main(String[] args) throws FileNotFoundException { Scanner scanner = new Scanner(new File("wordlist.txt")); String word = "Me"; try { while (scanner.hasNextLine()) { if (scanner.nextLine().equalsIgnoreCase(word)) { System.out.println("word found"); // word is found, no need to search the rest of the dictionary return; } } System.out.println("word not found"); } finally { scanner.close(); } } }
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