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Java Masterclass for Software Developers

Implementing a New Class

Explore how to implement a Java class with constructors, including default and initializing constructors. Understand method interactions within the class, such as calling one method from another, and learn programming tips for maintaining efficient and error-free code. Discover how to use convenience methods and incorporate a main method to test your class effectively.

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The Name class

We finally complete the implementation of the class Name, as shown below:

Java
/** Name.java by F. M. Carrano
    A class of names, each containing a first name and a last name.
*/
public class Name
{
   private String first; // First name
   private String last;  // Last name
	
   /** Creates a default name whose first and last names are empty. */
   public Name()
   {
      first = ""; // Empty string
      last = "";
   } // End default constructor
	
   /** Creates a name whose first and last names are the strings 
       firstName and lastName, respectively. */	
   public Name(String firstName, String lastName)
   {
      first = firstName;
      last = lastName;
   } // End constructor
	
   /** Sets the first name to the string firstName. */	
   public void setFirst(String firstName)
   {
      first = firstName; 
   } // End setFirst
	
   /** Sets the last name to the string lastName. */
   public void setLast(String lastName)
   {
      last = lastName;
   } // End setLast
	
   /** Sets the first and last names to the strings 
       firstName and lastName, respectively. */	
   public void setName(String firstName, String lastName)
   {
      setFirst(firstName);
      setLast(lastName);
   } // End setName
	
   /** Returns the first name as a string. */
   public String getFirst()
	{
      return first;
   } // End getFirst
	
   /** Returns the last name as a string. */
   public String getLast()
   {
      return last;
   } // End getLast
	
   /** Returns the entire name as a string. */	
   public String getName()
   {
      return first + " " + last;
   } // End getName
	
   /** Returns the entire name as a string. */
   public String toString()
   {
      return getName();
   } // End toString
	
   /** Gives the last name to otherName. */
   public void giveLastNameTo(Name otherName)
   {
      otherName.setLast(last);
   } // End giveLastNameTo
} // End Name

The default constructor sets the data fields to empty strings. If we did not initialize them, Java would set them each to null. The initializing constructor, as well as the set and get methods, have straightforward definitions.

Notice that some of these methods call each other. In particular, the method setName calls the methods setFirst and setLast. A method can invoke other methods in its class. We write

setFirst(firstName);

For example, in setName’s body without a receiving object. The object that receives the call to setName also receives the call to setFirst. We could write this statement as

this.setFirst(firstName);

if we prefer, but doing so is not necessary. Similarly, the method toString invokes the method getName.

✏️ Programming tip

When feasible, call already defined methods from within the definition of another method in the same class. Doing so avoids ...