Java文本文件搜索

Question

I have this method to search for a word in a text file but it constantly gives me back a negative result even tho the word is there??

public static void Option3Method(String dictionary) throws IOException
 { 
Scanner scan = new Scanner(new File(dictionary));
String s;
int indexfound=-1;
String words[] = new String[500];
String word1 = JOptionPane.showInputDialog("Enter a word to search for");
String word = word1.toLowerCase();
word = word.replaceAll(",", "");
word = word.replaceAll("\\.", "");
word = word.replaceAll("\\?", "");
word = word.replaceAll(" ", "");
while (scan.hasNextLine()) {
s = scan.nextLine();
indexfound = s.indexOf(word);
}
if (indexfound>-1)
{ 
JOptionPane.showMessageDialog(null, "Word found");
}
else 
{
JOptionPane.showMessageDialog(null, "Word not found");
 }

Answer 1

It is because you are replacing the value of the indexfound in your loop. So if the last line does not contains the word, the final value of indexfound will be -1.

I would recommand:

public static void Option3Method(String dictionary) throws IOException {
    Scanner scan = new Scanner(new File(dictionary));
    String s;
    int indexfound = -1;
    String word1 = JOptionPane.showInputDialog("Enter a word to search for");
    String word = word1.toLowerCase();
    word = word.replaceAll(",", "");
    word = word.replaceAll("\\.", "");
    word = word.replaceAll("\\?", "");
    word = word.replaceAll(" ", "");
    while (scan.hasNextLine()) {
        s = scan.nextLine();
        indexfound = s.indexOf(word);
        if (indexfound > -1) {
            JOptionPane.showMessageDialog(null, "Word found");
            return;
        }
    }
    JOptionPane.showMessageDialog(null, "Word not found");
}

Answer 2

Break the while loop if the word is found

while (scan.hasNextLine()) {
  s = scan.nextLine();
  indexfound = s.indexOf(word);
  if(indexFound > -1)
     break;
}

Problem with the above code is - the indexFound is getting overwritten. Your code ONLY works FINE, if the word is present in the last line of the file.

Answer 3

increament the indexfound in the while loop rather than indexfound = s.indexOf(word);

give

while (scan.hasNextLine()) 
   {
    s = scan.nextLine();
    if(s.indexOf(word)>-1)
        indexfound++; 

    }

using the indexfound value you can also find number of occurance in the file.