Data Structures Chapter 2 Quiz

Refer to objects

does not refer to anything

error because variable no longer refers to anything

• Instance Variables - private - variable declaration
• Constructors - public - method responsible for initializing instance variables
• Methods - public - does computations that access the class's instance variables. Two types include accessor methods and modification methods

Accessor methods have a return type because they are used to get information on an object. Modification methods have a void return type because they make some change to the variables but do not return information.

• public Throttle()
• {
•      top = 1;
•      position = 0;
• }

• public Throttle( int size, int initial)
• {
•      if ( size <= 0 )
•           throw new IllegalArgumentException("size<=0: " +size);
•      if ( initial <= 0 )
•           throw new IllegalArgumentException("initial<=0: " +initial);
•      if ( initial > size )
•            throw new IllegalArgumentException("initial too large: " +initial);
•      top = size;
•      position = initial;
• }

An accessor method does not alter an object but provides information on it.  A modification method changes an objects instance variables.

• public boolean isAboveHalf()
• {
•      return(getFlow() > 0.5);
• }

Java automatically provides a no argument constructor that sets each instance variablet o its initialization value.