CS 307 Fall 03 Midterm 1 Solution and Criteria

1 Criteria

For all A-F the answer as below (ignore caps, spacing and line breaks) or -2
For G-H, words to the effect of those in the answer or -2. Use -1 at your disgression

A
1 26 65

B
Runtime error due to an array index out of bound exception.
This was an unintended runtime error so the intened asnwer

13

was also accepted.

C
5 3
5 3 10 9
6 2 10 9
5 3

D
Kit-Kat 200 Crunchy
Kit-Kat 200 Crunchy
Kit-Kat 600 Crunchy
Kit-Kat 600 Crunchy

E
Snickers 300 with Peanuts
Snickers 300 with Peanuts
Snickers 500 with Peanuts
Snickers 300 with Peanuts

F
false
true
Snickers 200 with Peanuts
Snickers 200 with Peanuts

G
Runtime error due to a Null Pointer Exception. When cList is created it has 3 ChocolatyCancy object variables that are all null. There are 0 ChocolatyCandy objects. (or words to that effect)

H
SugaryCandy will not compile becuase it extends Candy but does not proivde an implemenation for the abstract method getDescriptor. If this were not a syntax error, then I could create an object for which a beahavior is not defined. In other words there is no code to carry out a method,

I
Polymorphism allows an object variable to hold the memory address of any object of that type, or any object vthat is a descendant of the declared type of the object vairable, or if the data type is an interface any classes that implement the interface.

J
Syntax error. iMycalories is declared with private access, thus code in a class other than Candy cannot access that variable.

Question 4 on back


2

int[] numOfSuit = new int[4];
for(int i = 0; i < hand.length; i++)
	numOfSuit[hand[i].getSuit()]++;

boolean flush = false;
for(int i = 0; i < numOfSuit.length; i++)
	if( numOfSuit[i] >= 5 || numOfSuit[i] == hand.length )
		flush = true;

return flush;

/* simple array processing question. Most people did great. */


3

int[] result = new int[numCols()];
int max = 0;
for(int col = 0; col < numCols(); col++)
{	max = myCells[0][col];
	for(int row = 0; row < numRows(); row++)
	{	if( getVal(row, col) > max )
			max = getVal(row,col);
	 	if( rhs.getVal(row, col) > max )
	 		max = rhs.getVal(row,col);
	}
	result[col] = max;
}
return result;

/* The biggest problems I saw on this question were not initializing max to a proper value for each column. Many people assigned it 0 for each column, but what if all values for that column, in both matrices were negative? The second big problem, which is a lot more serious, was confusion between rhs, a Matrix variable, and rhs.myCells, the 2 dimensional array of ints inside the Matrix object. Saying things like rhs[row][col] shows a fundamental misunderstanding between an object variable and the instance varaibles that object uses to model something.
*/

4
public class RoadSection
{	private boolean hilly;
	private boolean curvy;
	private boolean div;
	pribate int lanes;
	
	public RoadSection()
	{	hilly = false;
		curvy = false;
		div = false;
		lanes = 2;
	}
	
	public RoadSection(boolean h, boolean c, boolean d, int la)
	{	hilly = h;
		curvy = c;
		div = d;
		lanes = la;
	}
	
	public boolean slow()
	{	return (hilly || curvy || (!div && lanes < 3));	}
	
	public boolean isHighway()
	{	return div && lanes >= 4;	}
	
	public boolean equals(Object other)
	{	RoadSection r = (RoadSection)other;
		return hilly == r.hilly && curvy == r.curvy && div == r.div &&
			lanes == r.lanes;
	}
	
	public String to String()
	{	String h = (hilly) ? "Hilly," : "Flat,";
		String c = (curvy) ? "Curvy," : "Straight,";
		String d = (div) ? "Divided," : "Undivided, ";
		return lanes + " lanes, " + h + c + d;
	}
}

-1 per missing instance var (may be named different, essentially need 4)
-2 if any instance vars not declared private
-3 per missing method or constructor
-1 if any mutators or accessors included. The problem specifcally said to not include any other accessors or mutators.
-1 minor logic error in a method (ignore minor syntax errors) max 1 off per method
-2 major logic error in a method (ignore minor syntax errors) max 2 off per method

Send me scores for yoru seciton

FirstName LastName<tab>rawScore (out of 100)

Add up points off and subtract from 100 for raw score.