Passing String variables to Java method not working, but hard-coded string working?

Question

I'm having a strange issue. I'm trying to pass a number of String variables denoting a user's dislikes to a predefined Java method that works by comparing these dislikes to the key ingredients stored as a String array in a Recipe object array.

The method works fine when I hard-code a dislike, such as "Beef", but when I assign the dislikes to an instance String variable kw1 using user1.getDislikes(0), the method does not perform correctly - it returns recipes that have "Beef" as a keyword, when it shouldn't.

I know the String is being passed and assigned correctly as I used a Toast to display kw1 upon returning valid results.

I've tried adding toString() in numerous places as IntelliJ was being picky about it earlier, despite claiming it is redundant, but it hasn't worked here.

Here's the section I'm having difficulty with:

if ((SetRecipes.recipes[index].searchkeywords2(kw1, kw2, kw3))) //Not working unless words (e.g. "Beef") are hardcoded for some reason. kw1 variable being assigned correctly, as shown by Toast.
         {
            temp[validRecipe] = index;

            validRecipe++;
         } //if

The full code can be found below. Any help is greatly appreciated!

public class SuggestResult extends Activity
{

   String kw1, kw2, kw3;

   static TextView [] recipeText = new TextView[8];

   @Override
   public void onCreate(Bundle savedInstanceState)
   {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.suggest_results);
      User user1 = (User)getIntent().getSerializableExtra("user1");

      kw1 = user1.getDislikes(0).toString();
      kw2 = user1.getDislikes(1).toString();
      kw3 = user1.getDislikes(2).toString();

      /*
      kw1 = "null";
      kw2 = "null";
      kw3 = "null";
      */

      recipeText[0] = (TextView)findViewById(R.id.recipeSuggestText1);
      recipeText[1] = (TextView)findViewById(R.id.recipeSuggestText2);
      recipeText[2] = (TextView)findViewById(R.id.recipeSuggestText3);
      recipeText[3] = (TextView)findViewById(R.id.recipeSuggestText4);
      recipeText[4] = (TextView)findViewById(R.id.recipeSuggestText5);
      recipeText[5] = (TextView)findViewById(R.id.recipeSuggestText6);

      final int MAXRECIPES = 7;
      final int MAXTEXTFIELDS = 6;
      int[] temp = new int[MAXRECIPES];
      int validRecipe = 0;

      SetRecipes.setArray();

      for (int index = 0; index < MAXRECIPES; index++)
      {


         if ((SetRecipes.recipes[index].searchkeywords2(kw1, kw2, kw3))) //Not working unless words (e.g. "Beef") are hardcoded for some reason. kw1 variable being assigned correctly, as shown by Toast.
         {
            temp[validRecipe] = index;

            validRecipe++;
         } //if
      }

      if (validRecipe == 0)
      {
         Context context = getApplicationContext();
         CharSequence text = "No valid recipes found!";
         int duration = Toast.LENGTH_SHORT;
         Toast toast = Toast.makeText(context, text, duration);
         toast.show();
      }

      for (int index3 = 0; (index3 < validRecipe) && (index3 < MAXTEXTFIELDS); index3++)
      {
         recipeText[index3].setText((SetRecipes.recipes[temp[index3]].getName()).toString());

      }


      Context context = getApplicationContext();
      CharSequence text2 = kw1;
      int duration = Toast.LENGTH_SHORT;
      Toast toast = Toast.makeText(context, text2, duration);
      toast.show();


     }

}

searchkeywords2 method:

public boolean searchkeywords2(String choice1,String choice2, String choice3)
    {
        int ingredientsPresent = 0;


        for (int index = 0; index < keywords.length; index++)
        {
            if ((keywords[index] == choice1) || (keywords[index] == choice2) || (keywords[index] == choice3))
            {
                ingredientsPresent++;
            }
        }
        if (ingredientsPresent == 0)
        {
            return true;
        } else
        {
            return false;
        }


    }

Apologies, I've updated the explanation. The method is filtering recipes containing the keyword "Beef" when I pass "Beef" as a parameter, but not filtering recipes with beef when I pass kw1 as a parameter. — Ruairi McGowan, Dec 07 '14 at 01:44
So the interesting method is `searchkeywords2`? Can you add it to the question? — Tom, Dec 07 '14 at 01:45
Can you do a System.printf(kw*) ... a verify they are what you expect ... its not surprising that user1 is the result of a cast, and you are having a problem with something derived from that — nPn, Dec 07 '14 at 01:48
As I thought, you're doing the "string compare" part wrong. Read this question: [how do I compare Strings in Java](http://stackoverflow.com/questions/513832/how-do-i-compare-strings-in-java). — Tom, Dec 07 '14 at 01:51
Yes, nPn the Toast at the end of the code correctly displays "Beef" when the 'text2' variable is assigned to kw1, so I know that the String in kw1 is correct. — Ruairi McGowan, Dec 07 '14 at 01:51

score 2 · Accepted Answer · answered Dec 07 '14 at 01:51

2

keywords[index] == choice1 ...

This is the problem. Use .equals() function to compare strings, not ==

keywords[index].equals(choice1) etc.

answered Dec 07 '14 at 01:51

Dima

39,570
6
44
70

seems like the likely cause – nPn Dec 07 '14 at 01:55
@RuairiMcGowan I guess because `keywords[index]` is `null` (i.e. you have `null` elements in this array). A quick fix can be `choice1.equals(keywords[index])`, but you should check why you have `null` elements in that array and if they are supposed to be there. – Tom Dec 07 '14 at 02:05
It _shouldn't_ be null as it was working with the hard-coded strings as a parameter, BUT it is now working fully using `if (choice1.equals(keywords[index]) || choice2.equals(keywords[index]) || choice3.equals(keywords[index]))` Thanks to everyone for their help! – Ruairi McGowan Dec 07 '14 at 02:17
if `keywords[index]` is `null`, indeed, `keywords[index] == choice1` would work, but `keywords[index].equals(choice1)` would crash. Why do you have nulls in keywords? Does not sound like it is intended ... – Dima Dec 07 '14 at 04:00
Dima, you are correct, the keywords array was declared with 6 elements despite us using only 3 for our current recipes, this means keyword.length is 6 and the FOR loop tries to access the 4th element in the keyword array, which is null. Thanks for the explanation! – Ruairi McGowan Dec 07 '14 at 19:02

score 0 · Answer 2 · answered Dec 07 '14 at 04:06

0

Always use .equals to compare strings because == operator only compares references rather than data

answered Dec 07 '14 at 04:06

Aqib

396
4
13

score 0 · Answer 3 · answered Dec 07 '14 at 08:23

When we use == operator, it checks if the objects point to the same location on the memory but the .equals on the other hand apart from checking if the objects point to the same location also checks for the equality of the object content in the memory location, thus providing double check. You can also override the equals class to perform other checks. So, always use the .equals to check equality of 2 objects.

Passing String variables to Java method not working, but hard-coded string working?

3 Answers3