Getting ready for Java test 3

Whenever an Interface is implemented by a subclass

• All abstract methods in the interface must be implemented in the super class

• All methods in the subclass must use @override notation before each method

• All abstract methods in the interface must be implemented in the sub class

• All methods in the subclass must use @Override notation before each method

What is the purpose of the Comparator class

• To sort a collection in ascending order

• To sort a collection in descending order

• To sort the collection in the ascending order of the state variable which is unique within that class

• To allow a collection to be sorted in different ways depending on the Comparator used

Java Interfaces

• Allows the behaviour of multiple class types to be implemented

• Merges a subclass with the parental class

• Provides a means of communications between Classes

• Allows a class to not inherit from The Object class

The Comparable interface has one abstract method which needs to be implemented. The method is

• comparetoo(Object o)

• compareToo(Object o)

• compareto(Object o)

• compareTo(Object o)

What is the return type of the compareTo method

• int

• String

• ArrayList

• Same type as objects being compared

Which is returned when using compareTo where this object is less that the parameter object

• Zero

• Positive

• Negative

• Parameter object

• This Object

What word has been left out of the following statement:

java.util. .sort(list);

• Collection

• collection

• collections

• Collections

Which is the correct implementation of the compareTo method for a Circle class based on ascending radius size

• public int compareTo(Circle c) { if (this.radius<c.radius) return -1;

  if (this.radius>c.radius) return 1;

  return 0; }

• public int compareTo(Circle c) { if (this.radius<c.radius) return +1; else if (this.radius>c.radius) return -1;

  else if (this.radius>c.radius) return 0; }

• public int compareTo(Circle c) { if (this.radius<c.radius) return -1; else if (this.radius>c.radius)

  return +1;

  else if (this.radius>c.radius) return 0; }

Which of the following is true about an abstract class

• Cannot use unless @override is included before implementation

• Cannot use unless @Override is included before implementation

• It can optionally be implemented in the subclass

• It only has header (no body)

If the comparator interface is implemented, which abstract method has to be written in the subclass

• compareTo

• compareTo

• Compare

• compare