When writing classes, we often make all of our instance variables private. However, we still might want some other classes to have access to them, we just don’t want those classes to know the exact variable name. To give other classes access to a private instance variable, we would write an accessor method (sometimes also known as a “getter” method).

public class Dog{
  private String name;

  //Other methods and constructors

  public String getName() {
    return name;
  }
}

Even though the instance variable name is private, other classes could call the public method getName() which returns the value of that instance variable. Accessor methods will always be public, and will have a return type that matches the type of the instance variable they’re accessing.

Similarly, private instance variables often have mutator methods (sometimes known as “setters”). These methods allow other classes to reset the value stored in private instance variables.

public class Dog{
  private String name;

  //Other methods and constructors

  public void setName(String newName) {
    name = newName;
  }

  public static void main(String[] args){
    Dog myDog = new Dog("Cujo");
    myDog.setName("Lassie");
  }
}

Mutator methods, or “setters”, often are void methods — they don’t return anything, they just reset the value of an existing variable. Similarly, they often have one parameter that is the same type as the variable they’re trying to change.