Searching a string from keywords in an array

Question

I can't figure out why this does not work? I am trying to locate keywords from an array in a string and to println the index number of the array in the console. I have tried the "if" statement both with and without the boolean "true"

public class Testing 
{
    public static void main(String[] args)
    {
    String[] keywords = new String[5];
    keywords[0] = "boat";
    keywords[1] = "car";
    String myString = "the banana car";

          for(int a = 0; a <= keywords.length; ++a)

          {

             if(myString.contains(keywords[a])== true)
                {

                System.out.println(myString.indexOf(keywords[a]));
                }
             else
                {
                System.out.println("Those keywords are not in that string"); 
                }

           }
     }
}

Alya'a Gamal · Accepted Answer · 2013-03-31 19:06:57Z

4

String[] keywords = new String[5];////////////here you have array with 5 element
    keywords[0] = "boat";
    keywords[1] = "car";
//////////you just full index 0 and index 1

then you for loop on the length of keywords

for (int a = 0; a <keywords.length; a++) 
//////keywords.length=5 , index 0 and index 1 have a value but the other index is empty

So :

you need to full the keywords array :

 keywords[0] = "boat";
 keywords[1] = "car";
 keywords[2] = //////////;
 keywords[3] = //////////;
 keywords[4] = ///////;

or make the length =2:
```
String[] keywords = new String[2];
```

edited Mar 31, 2013 at 19:06

answered Mar 31, 2013 at 18:52

Alya'a Gamal

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2 Comments

Rexx Over a year ago

Thanks - I just tried changing String[] keywords = new String[2]; and it still doesn't work :(

Alya'a Gamal Over a year ago

try to change the for loop to :for (int a = 0; a <keywords.length; a++) don't use a <=keywords.length

Maciej Cygan · Accepted Answer · 2013-03-31 18:53:55Z

1

you are missing 3 extra elements as you have declared your String array to contain 5 elements

String[] keywords = new String[5];
    keywords[0] = "boat";
    keywords[1] = "car";

answered Mar 31, 2013 at 18:53

Maciej Cygan

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Comments

Maroun · Accepted Answer · 2013-03-31 18:54:01Z

1

a <= keywords.length should be a < keywords.length and you should fill the array if you declared it to be of size 5 to have 5 elements (from 0 to 4).

Arrays are zero based in Java, so if you have array of length n then the indexes are from 0 to n-1 (which will sum up to n)

Another important thing:

In if(myString.contains(keywords[a])== true), the == true is redundant, since myString.contains(keywords[a]) returns true or false and here you only want to check this. So it's a better style to remove the == true.

answered Mar 31, 2013 at 18:54

Maroun

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Comments

Kakalokia · Accepted Answer · 2013-03-31 18:54:30Z

1

You haven't initalized all the elements of your keywords, therefore you are going to get a NullPointerException

If you only want to check the first two elements that you initialized, change your for loop to the following:

for (int a = 0; a <= 1; ++a)

answered Mar 31, 2013 at 18:54

Kakalokia

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Comments

Aubin · Accepted Answer · 2013-03-31 18:57:38Z

1

This program:

public class Testing {

   public static void main( String[] args ) {
      String[] keywords = new String[]{ "boat", "car" }; // Only 2 not 5
      String myString = "the banana car";
      for( String keyword : keywords ) {
         int index = myString.indexOf( keyword );
         if( index > -1 ) {
            System.out.println(
               "Keyword '" + keyword + "' is in the string '" +
               myString + "' at position " + index ); 
         }
         else
         {
            System.out.println( "Keyword '" + keyword +
               "' is not in the string '" + myString + "'" ); 
         }
      }
   }
}

outputs:

Keyword 'boat' is not in the string 'the banana car'
Keyword 'car' is in the string 'the banana car' at position 11

answered Mar 31, 2013 at 18:57

Aubin

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2 Comments

A4L Over a year ago

+1 for using indexOf for the search and saving the redundant contains. also for the altered output in the else block.

Rexx Over a year ago

Novice java guy says a big "Thank You" to all of you :)

Jiri Kremser · Accepted Answer · 2013-03-31 18:55:09Z

0

public static void main(String[] args) {
    String[] keywords = {"boat", "car"};
    String myString = "the banana car";
    for(int i = 0; i < keywords.length; i++) {
        System.out.println(myString.contains(keywords[i]) ? myString.indexOf(keywords[i]) : "Those keywords are not in that string");

    }
}

..should work

answered Mar 31, 2013 at 18:55

Jiri Kremser

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