What will the compiler do with the following method: 

class Entry
{
  . . . . .

  // methods
  public boolean equals( Object other )
  {
    return name.equals( other.name );
  }

  . . . . . 
}

A good answer might be:

It will find a syntax error because name is not an instance variable of Object.

Test Program

These ideas are a little bit confusing. It is a good idea to write a test program to see if things work as expected: 

import java.util.* ;
import java.io.*;

class Entry
{
  String name;
  String number;

  // constructor
  Entry( String n, String num )
  {
    name = n; number = num;
  }

  // methods
  public boolean equals( Object other )
  {
    return name.equals( ((Entry)other).name );
  }

  public String toString()
  {
    return "Name: " + name + " Number: " + number;
  }
 
}

class PhoneBookTest
{
  public static void main ( String[] args) throws IOException
  {
    Vector phone = new Vector( 10 );

    phone.addElement( new Entry( "Amy", "123-4567") );
    phone.addElement( new Entry( "Bob", "123-6780") );
    phone.addElement( new Entry( "Hal", "789-1234") );
    phone.addElement( new Entry( "Deb", "789-4457") );
    phone.addElement( new Entry( "Zoe", "446-0210") );

    // look for Hal in phone using our equals() method    
    int spot = phone.indexOf( new Entry( "Hal", "") ) ;

    System.out.println( "indexOf returns: " + spot ) ;
  }
}

The entry we build as the target of the search has an empty string for the phone number. The equals() method will compare it with entries that have a non-empty phone number. But equals() is written to look only at the name of the two entries, so this is OK.

QUESTION 22:

What will the program write?

Click Here after you have answered the question