toString Accessor Method

The toString accessor method is an overridden method that is included in classes to provide a description of a specific object. It returns a sting description of the instance variables of the object. The method is called automatically to try to convert an object to a String when needed.

If System.out.print or System.out.println is passed an object, that object’s toString method is called and the returned string is printed.

If you try to just print the object…

It won’t print the information that you want.

public class Minion
{
    // Start by defining instance variables that you'll want to access later via the accessor methods
    private double height;
    private String name;
    private String hair;
    private int eyes;

    // Default Constructor
    //String n, int c
    public Minion()
    {
        height = 3.7;
        name = "Bob";
        hair = "None";
        eyes = 2;
    }

    // Overloaded Constructor
    public Minion(double h, String n, String hr, int e)
    {
        height = h;
        name = n;
        hair = hr;
        eyes = e;
    }
    // Accessor Methods!
    public double getHeight()
    {
        return height;
    }
    public String getName()
    {
        return name;
    }
    public String getHair()
    {
        return hair;
    }
    public int getEyes()
    {
        return eyes;
    }
}
// Create minion object Kevin
Minion kevin = new Minion(4.10,"Kevin","Sprout-Cut",2);

// Print Kevin Object
System.out.println(kevin);

REPL.$JShell$12$Minion@f979182

The toString Method

When the System.out.println() is used, the toString method within the class is automatically called to print the object’s values. image

Popcorn Hack

Return all the instance variables in Minion so that we can directly print the object values of the minion Kevin.

public class Minion
{
    // Start by defining instance variables that you'll want to access later via the accessor methods
    private double height;
    private String name;
    private String hair;
    private int eyes;

    // Default Constructor
    //String n, int c
    public Minion()
    {
        height = 3.7;
        name = "Bob";
        hair = "None";
        eyes = 2;
    }

    // Overloaded Constructor
    public Minion(double h, String n, String hr, int e)
    {
        height = h;
        name = n;
        hair = hr;
        eyes = e;
    }
    // Accessor Methods!
    public String toString()
    {
        // Code here
    }
}
// Create minion object Kevin
Minion kevin = new Minion(4.10,"Kevin","Sprout-Cut",2);

// Print Kevin Object
System.out.println(kevin);

Name:Kevin
Height: 4.1
Hair:Sprout-Cut
Eyes: 2

When Creating a toString Accessor Method…

  • You cannot change the header of the method public String toString() -> cannot change this
  • Always returns string
  • Doesn’t take any parameters
  • When System.out.printIn(object) is called on an object:
    • toString method is called
    • returned string is printed