Final Examination

• Before you answer any questions, write your name and perm number.
• Read each question carefully.  Make sure that you clearly understand each question before answering it.
• Put your answer to each question on its own page.
• You may wish to work out an answer on scratch paper before writing it on your answer page; answers that are difficult to read may lose points for that reason.

1. (10 points) For the Color constructors below, indicate whether there is a compile-time error, an execution-time error, or that the constructor will work.  Assume the following declaration and initialization:

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float r = 0; 

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      B. (5 points) Would it ever make sense to create a private static method?  Explain.

3. A. (7 points) You are given the following declaration.

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         int s, n, delta;


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Give a java expression that evaluates to a random element in the set:
 
{s, s + delta, s + 2*delta, s + 3*delta, ..., s + n*delta}.
 
For example, if s = -15, n = 4, and delta = 10, then your expression evaluates to a random element in the set
 
{-15, -5, 5, 15, 25}.
B. (8 points) Give a java expression that evaluates to a random element in the set: {1, 2, 4, 8, 16, 32, 64}.
You get 6 points, if you can give java statements to do this (but not a simple expression).

1. (3 points) Write a method abs whose only parameter, i, is a double and which returns a double whose value is the absolute value of i.  For example, abs(-3.0) would return a double of value 3.0; abs(3.0) would return a double of value 3.0.

Instead of writing this method, you can give a pre-defined method, if you know one.
 

2. (10 points) Using the method abs (even if you did not answer part 1), write a method called max that has an array, a, of double as a parameter, and returns a double whose value is the absolute value of the element whose absolute value is maximum over all the elements in a.  For example, if max were passed the array whose values are {-3.0, 4.0, -5.0, 6.0, -7.0}, then max would return a double whose value was 7.0.

 
3. (10 points) Using the method max (even if you did not answer part 2), write a method maxes that has 2 parameters:
1. a 2-dimensional array b of doubles
2. a 1-dimensional array c of doubles
Method maxes, for each element, i, of c, puts the maximum absolute value of the elements in row b[i] into c[i].  If b[i] does not exist, then set c[i] to -1.  Method maxes has no return value.  For example, given the declarations:


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double c[] = new int[3], b[][] = {{1, 2, 3}, {-1, -2, -3}} 

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Then maxes would put 3 into c[0], 3 into c[1], and -1 into c[2].
 
4. (2 points) When maxes gets invoked with its 2 array arguments, does the array corresponding to c actually get changed by the maxes method?

 

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int x[][] = {{-1, 0, 1, 2, 3}, {-4, -5, -6, -7}, {8, 9, 10}}
What is the value x[x.length-1][x[x.length-2].length-3]?  It may be a good idea to show your work.

• an int x coordinate of the location of its square
• an int y coordinate of the location of its square
• an int e representing the edge length of its square
• a Color c representing the color of its square
• a Node object, called next, representing the next node in the list.

• a constructor that takes  4 paramenters: 3 ints and a Color that correspond to its attributes.  It sets the attributes of the Node being constructed to the values of the parameters passed.  It leaves its next attribute null (not referring to any Node object).
• public get and set methods for each of its attibutes.
• a public draw method that takes a Graphics object, g, as a parameter, and draws the corresponding filled square on g.
• a public insert method that takes as a parameter a Node d and:
• sets d's next attribute to refer to whatever this Node's next attribute referred to,
• sets this Node's next attribute to refer to d,
• returns a reference to the updated Node.
For example, if we had: 

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Node a = new Node(3,4,5,Color.red), b = new Node(6,7,8,Color.black); 

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and we executed:

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a.insert(b) 

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then a's next field would refer to b; b's next field would still be null, and the returned value would be a reference to a.