ArrayLists and Iterators

Read this chapter about lists and the useful methods that are available for adding and inserting elements into a list.

29. Playful Program

Answer:
Of course. Playing with things always helps to understand them.

Playful Program

Here is the program, just as before, but with some statements added to show what is going on.

import java.util.* ;

class Entry
{
  private String name;
  private String number;

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

  // methods
  public String getName()
  {
    return name ;
  }

  public String getNumber()
  {
    return number ;
  }

  public boolean equals( Object other )
  {
   
    System.out.print  ("    Compare " + other + " To " + this );
    System.out.println(" Result: " +  name.equals( ((Entry)other).name ) );
    return getName().equals( ((Entry)other).getName() );
  }

  public String toString()
  {
    return "Name: " + getName() + "; Number: " + getNumber() ;
  }
 
}

public class PhoneBookTest
{
  public static void main ( String[] args)
  {
    ArrayList<Entry> phone = new ArrayList<Entry>();

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

    // Look for Hal in phone. The indexOf() method uses the
    // equals(Object) method of each object in the list.
    // 

    System.out.println("Begin Search" ); 
    Entry target = new Entry( "Hal", null );
    
    int spot = phone.indexOf( target ) ;
    System.out.println("End Search" );

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

Copy the program to a file and run it. Play with it for a while.

Question 28:

Could the program be altered so that it searches for a name entered by the user?

(It would be good practice for you to do this before you go on.)