A+ Answers

Question 1

Write static methods as follows:

double sum(double[] a) – returns the sum of the entries in the array a.

double[] fill(int n, double v) – returns an array of n doubles, all of whose values are v.

double[] random (int n) – return an array of n random doubles.

double min(double[] a) – returns the minimum element of the array a.

double max(double[] a) – returns the maximum element of the array a.

double average(double[] a) – returns the average (or mean) of the elements of the array a.

double variance(double[] a) – returns the variance of the elements of the array a (note: this method should call your average method).

double stdDev(double[] a) – returns the standard deviation of the elements of the array a (note: this method should call your variance method).

double[] read() – reads an array from the keyboard and returns it (read the number of elements first, and then that many numbers).

void print(double[] a) – prints an array, a, on a single line with commas between elements (do NOT use Arrays.toString()).

Write a Main class with a main method that tests your methods appropriately (i.e. by calling each method at least once with various inputs), and printing the results

Question 2

Consider the following method and method call:

     public static int inc(int a) {        

   a++;

return a; }

     int a = 10;    

  int b = inc(a + 12);    

  int c = inc(a);

System.out.println(a);    

 System.out.println(b);   

  System.out.println(c);

What is the output from this code? Carefully explain your answer (i.e. carefully show how the method inc is called).

Question 3

Consider the following method and method call:

     public static int[] inc(int[] a) {        

   a[0]++;

return a;

}

     int[] a = { 10, 20, 30, 40 };    

  int[] b = inc(a);   

  System.out.println(b[0]);     

System.out.println(a[0]);

What is the output from this code? Carefully explain your answer (i.e. carefully show how the method inc is called).

Question 4

Consider the following code:

     int[] a = { 10, 20, 30, 40 };    

  int[] b = a;  

    int[] c = { 10, 20, 30, 40 };    

 System.out.println(a == b);     

System.out.println(a == c);

What is the output from this code? Carefully explain your answer.