Interfaces and Polymorphism - Java Concepts - page 537

interface in an implements clause. It should then implement the method or
methods that the interface requires.

class ClassName implements Measurable
{
public double getMeasure()
{
Implementation
}
Additional methods and fields
}

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391

A class can implement more than one interface type. Of course, the class must then
define all the methods that are required by all the interfaces it implements.

Let us modify the BankAccount class to implement the Measurable interface.

public class BankAccount implements Measurable
{
public double getMeasure()
{
return balance;
}
. . .
}

Note that the class must declare the method as public , whereas the interface need
notȌall methods in an interface are public.

Similarly, it is an easy matter to modify the Coin class to implement the
Measurable interface.

public class Coin implements Measurable
{
public double getMeasure()
{
return value;
}
. . .
}

In summary, the Measurable interface expresses what all measurable objects have
in common. This commonality makes the DataSet class reusable. Objects of the
DataSet class can be used to analyze collections of objects of any class that