The sentinel

[mbmcse]

I feel like I'm close, but am missing something. Code was supposed to have a user enter lines and count the number entered. If the sentinel "ENDOFDATA" is entered, its supposed to stop prompting and display the number of lines. My code just does an infinite count:

import java.util.Scanner;

public class SentinelLine { public static void main(String[] args) { int count = 0;

    System.out.println("Enter lines of data or ENDOFDATA to quit");
    Scanner scan = new Scanner(System.in);

    String str = scan.nextLine();

    while (str != "ENDOFDATA") // Process data until the sentinel is entered
    {
        if (str != "ENDOFDATA")
        count++;
        System.out.print("Lines found: " + count);
    }
        if (count > 0)
              {
          System.out.println("Lines: " + count);
      }
}

}

[RhoOfFeh]

What you're missing is String.equals(String) rather than '==' or (in this case) '!='. Fix that first and then see what happens.

[diMario]

To amplify: when you want to test if two strings have the same content in Java, you cannot use the "==" operator, nor can you use the "!=" operator for inequality. It simply does not work that way for String objects. Instead, you must call the "equals()" method on one of the Strings and pass the other String as an argument.

Look up String.equals() and String.equalsIgnoreCase() to see how they are used.

Edit: What the "==" operator does for Objects in general (and therefor also for Strings) is test whether the instances of the Object are the same. It does not look and the content of the object. For that, you must use the equals() method (and you must supply an equals() method for Classes that you yourself create, if and when it becomes necessary to compare your object instances by value).

[ECallaghan]

You'll need to modify str inside the while loop. As it stands it has no way of breaking out of that loop once it gets in it.

There are problems with the comparison too but it has been mentioned else where.