When 2 or more methods in the same class have the same name they are said to be what?

  Cons(Object first, FunList rest) {
    this.first = first;
    this.rest = rest;
    }

While the use of the same name for different kinds of program entities is widely accepted as good programming practice, the use of one name for several different fields or methods is more controversial. A Java subclass B can introduce a field with exactly the same name n as a field in its superclass A. The inherited field is not overridden (what would overriding mean in this context?); it is merely ``shadowed''. When the name n appears in a method of B, its meaning depends on the type of the receiver. If the receiver is this, then the new field n introduced in B is meant. But if the receiver has type A rather than B, then the old field n introduced in A is meant. Warning: duplicate field names can be the source of insidious program errors that are very difficult to diagnose. For this reason, we strongly recommend against using them.

Duplicate method names are less controversial but can still be dangerous. In a class, Java permits the same method name to be used for different methods as long as their argument lists do not identical the same length and same types. The practice of defining more than one method in a class with same name is called method overloading. Java resolves overloaded method names using the types of the argument expressions. When the Java compiler encounters a method invocation involving an overloaded method, it determines the types of the method arguments and uses this information to select the ``best'' (most specific) match from among the alternatives. If no best method exists, the program is ill-formed and will be rejected by the Java compiler.

We urge restraint in using the same name for different methods involving the same number of arguments. Since static type information is used to resolve which method is meant, program errors may be difficult to find because the programmer may not infer the correct static type when reading the code.

Given below is an extract from the -- Java Tutorial, with slight adaptations.

A class that is derived from another class is called a subclass (also a derived class, extended class, or child class). The class from which the subclass is derived is called a superclass (also a base class or a parent class).

A subclass inherits all the members (fields, methods, and nested classes) from its superclass. Constructors are not members, so they are not inherited by subclasses, but the constructor of the superclass can be invoked from the subclass.

Every class has one and only one direct superclass (single inheritance), except the Object class, which has no superclass, . In the absence of any other explicit superclass, every class is implicitly a subclass of Object. Classes can be derived from classes that are derived from classes that are derived from classes, and so on, and ultimately derived from the topmost class, Object. Such a class is said to be descended from all the classes in the inheritance chain stretching back to Object. Java does not support multiple inheritance among classes.

The java.lang.Object class defines and implements behavior common to all classes—including the ones that you write. In the Java platform, many classes derive directly from Object, other classes derive from some of those classes, and so on, forming a single hierarchy of classes.

The keyword extends indicates one class inheriting from another.

Here is the sample code for a possible implementation of a Bicycle class and a MountainBike class that is a subclass of the Bicycle:

public class Bicycle {

    public int gear;
    public int speed;

    public Bicycle(int startSpeed, int startGear) {
        gear = startGear;
        speed = startSpeed;
    }

    public void setGear(int newValue) {
        gear = newValue;
    }

    public void applyBrake(int decrement) {
        speed -= decrement;
    }

    public void speedUp(int increment) {
        speed += increment;
    }

}

public class MountainBike extends Bicycle {

    // the MountainBike subclass adds one field
    public int seatHeight;

    // the MountainBike subclass has one constructor
    public MountainBike(int startHeight, int startSpeed, int startGear) {
        super(startSpeed, startGear);
        seatHeight = startHeight;
    }

    // the MountainBike subclass adds one method
    public void setHeight(int newValue) {
        seatHeight = newValue;
    }
}

A subclass inherits all the fields and methods of the superclass. In the example above, MountainBike inherits all the fields and methods of Bicycle and adds the field seatHeight and a method to set it.

Accessing superclass members

If your method overrides one of its superclass's methods, you can invoke the overridden method through the use of the keyword super. You can also use super to refer to a when both the superclass and the subclass use the same variable name, the superclass variables is said to be hidden/shadowed by the subclass variablehidden field (although hiding fields is discouraged).

Consider this class, Superclass and a subclass, called Subclass, that overrides printMethod():

public class Superclass {

    public void printMethod() {
        System.out.println("Printed in Superclass.");
    }
}

public class Subclass extends Superclass {

    // overrides printMethod in Superclass
    public void printMethod() {
        super.printMethod();
        System.out.println("Printed in Subclass");
    }
    public static void main(String[] args) {
        Subclass s = new Subclass();
        s.printMethod();
    }
}

Printed in Superclass.
Printed in Subclass

Within Subclass, the simple name printMethod() refers to the one declared in Subclass, which overrides the one in Superclass. So, to refer to printMethod() inherited from Superclass, Subclass must use a qualified name, using super as shown.

Subclass constructors

A subclass constructor can invoke the superclass constructor. Invocation of a superclass constructor must be the first line in the subclass constructor. The syntax for calling a superclass constructor is super() (which invokes the no-argument constructor of the superclass) or super(parameters) (to invoke the superclass constructor with a matching parameter list).

The following example illustrates how to use the super keyword to invoke a superclass's constructor. Recall from the Bicycle example that MountainBike is a subclass of Bicycle. Here is the MountainBike (subclass) constructor that calls the superclass constructor and then adds some initialization code of its own (i.e., seatHeight = startHeight;):

public MountainBike(int startHeight, int startSpeed, int startGear) {
    super(startSpeed, startGear);
    seatHeight = startHeight;
}

Note: If a constructor does not explicitly invoke a superclass constructor, the Java compiler automatically inserts a call to the no-argument constructor of the superclass. If the superclass does not have a no-argument constructor, you will get a compile-time error. Object does have such a constructor, so if Object is the only superclass, there is no problem.

Access modifiers (simplified)

Access level modifiers determine whether other classes can use a particular field or invoke a particular method. Given below is a simplified version of Java access modifiers, assuming you have not yet started placing your classes in different packages i.e., all classes are placed in the root level. A full explanation of access modifiers is given in a later topic.

There are two levels of access control:

1. At the class level:

   • public: the class is visible to all other classes
   • no modifier: same as public

2. At the member level:

   • public : the member is visible to all other classes
   • no modifier: same as public
   • protected: the member is visible to sub classes only
   • private: the member is not visible to other classes (but can be accessed in its own class)

When 2 or more methods in the same class have the same name it is called method?

When you create two or more methods with the same name but they have a different parameter lists this is called method overloading?

Can a class have two methods with the same name?

What is it called when methods are used with the same name?