22. Copy constructors

• Cloning is a potentially dangerous action, because it can cause unintended side effects.

• For example, if the object being cloned contains a field referencing another object, then, after the clone is made, the field in the clone refers to the same object as does the field in the original.

• Copy constructors provide an attractive alternative to the Object.clone():

  
  public class Book extends Product implements Printable
  {
      public static void main (String[] args )
      {
          Book first = new Book( "12345", "Irish stories and legends", 14.50, "folklore" );
          Book second = new Book( first );
          first.print();
          second.print();
      }
  
      private String author;
  
      // Constructor
      public Book(
          String code,
          String description,
          double price,
          String author )
      {
          super( code, description, price );
          this.author = author;
      }
  
      // Copy constructor.
      public Book( Book another )
      {
          this( another.code, another.description, another.price, another.author );
      }
  
      // implement the Printable interface
      @Override
      public void print() 
      {
          System.out.println(
              "Code:          " + code);
          System.out.println(
              "Description:   " + description);
          System.out.println(
              "Price:         " + price);
          System.out.println(
              "Autor:         " + author);
      }
  }//class Book
  
  

  For complete example, see CIS-257 Java Samples