CODEWITHSUNDEEP
java
neon_spandex
neon_spandex

Reputation: 13

Java Scanner.next() or method calling

I am writing a program that takes an input and searches a list of words for any of its anagrams. To do this, it calls a void method search that prints out 10 anagrams. Here is the code snippet that is causing me trouble:

public static void main(String[] args) throws Exception
   {
      Scanner input = new Scanner(System.in);
      System.out.println("Please enter a word: ");
      String word = input.next();
      System.out.println(word);
      search(word);
   }

This always prints out whatever word you input, but then it stops. When I used the debugger in jGRASP, I noticed that it doesn't even save any value to word! It also never calls the search class. The code freezes - it says that it's still running, but it doesn't do anything. However, if I have the user input an integer value after the word, like this:

Scanner input = new Scanner(System.in);
System.out.println("Please enter a word: ");
String word = input.next();
System.out.println(word);
System.out.println("Enter a number: ");
int example = input.nextInt();
search(word);

This will save a value to word, but not example, and the code freezes up like before!

EDIT: Here is the search method. words.txt is a list of words in the same folder.

public static void search(String input) throws Exception
   {
      Scanner words = new Scanner(new File("words.txt"));
      char[] alphabet = new char[] {'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z'};
      int[] inputLetters = new int[25];
      int[] wordLetters = new int[25];
      String[] anagrams = new String[10];
      int entries = 0;
      for(int a = 0; a < input.length(); a++)
      {
         for(int b = 0; b <= 25; b++)
         {
            if(input.charAt(a) == alphabet[b])
            {
               inputLetters[b]++;
            }
         }
      }
      while(entries < anagrams.length)
      {
         while(words.hasNext())
         {
            String comparison = words.next();
            for(int a = 0; a < comparison.length(); a++)
            {
               for(int b = 0; b < 25; b++)
               {
                  if(comparison.charAt(a) == alphabet[b])
                  {
                     wordLetters[b]++;
                  }
               }
            }
            if(inputLetters == wordLetters)
            {
               anagrams[entries] = comparison;
               entries++;
            }
         }
      }
     System.out.println(Arrays.toString(anagrams));
   }

Upvotes: 1

Views: 1025

Answers (1)

Marko Topolnik
Marko Topolnik

Reputation: 200168

Actually, it's clear as day. You don't need the debugger to find the endless loop.

Here are the key bits of code:

  int[] inputLetters = new int[25];
  int[] wordLetters = new int[25];

  while(entries < anagrams.length)
  {
        ....

        if(inputLetters == wordLetters)
        {
           ......
           entries++;
        }
     }
  }

Analysis:

  1. You loop as long as entries, initially 0, is less than anagrams.length;
  2. you increment entries if inputLetters == wordLetters;
  3. but clearly, the inputLetters reference can never be equal to the wordLetters reference. Each refers to its own array;
  4. therefore you fail to ever increment entries;
  5. therefore you have an endless loop.

Upvotes: 3

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