29 Javanotes 9.0, Quiz on Chapter 7

Quiz on Chapter 7

Question 1:

What is meant by the basetype of an array?

Question 2:

What is the purpose of the following variable-arity method? What are
the values of same(1,2,3), same(17,17,17,17),
and same(2)? Why?

static double same( int... value ) {
    for (int i = 1; i < value.length; i++) {
        if ( value[i-1] != value[i] )
            return false;
    }
    return true;
}

Question 3:

What does it mean to sort an array?

Question 4:

What is the main advantage of binary search over linear search? What is the
main disadvantage?

Question 5:

What is meant by a
dynamic array? What is the advantage of a dynamic array over a regular
array?

Question 6:

What does it mean to say that ArrayList is a
parameterized type?

Question 7:

Suppose that a variable strlst has been declared as

ArrayList<String> strlst = new ArrayList<String>();

Assume that the list is not empty and that all the items in the list
are non-null. Write a code segment that will find and print the string in the list
that comes first in lexicographic order.

Question 8:

Show the exact output
produced by the following code segment.

char[][] pic = new char[6][6];
for (int i = 0; i < 6; i++)
   for (int j = 0; j < 6; j++) {
      if ( i == j  ||  i == 0  ||  i == 5 )
         pic[i][j] = '*';
      else
         pic[i][j] = '.';
   }
for (int i = 0; i < 6; i++) {
   for (int j = 0; j < 6; j++)
      System.out.print(pic[i][j]);
   System.out.println();
}

Question 9:

Write a complete static method
that finds the largest value in an array of ints. The method
should have one parameter, which is an array of type int[]. The
largest number in the array should be returned as the value of the
method.

Question 10:

Suppose that temperature
measurements were made on each day of 2021 in each of 100 cities. The
measurements have been stored in an array

int[][]  temps  =  new  int[100][365];

where temps[c][d] holds the measurement for city number c
on the d
^th day of the year. Write a code segment that will
print out the average temperature, over the course of the whole year, for each
city. The average temperature for a city can be obtained by adding up all 365
measurements for that city and dividing the answer by 365.0.

Question 11:

Suppose that a class,
Employee, is defined as follows:

class Employee {
   String lastName;
   String firstName;
   double hourlyWage;
   int yearsWithCompany;
}

Suppose that data about 100 employees is already stored in an
array:

Employee[] employeeData = new Employee[100];

Write a code segment that will output the first name, last name, and hourly
wage of each employee who has been with the company for 20 years or more. Write two
versions of the code segment, one that uses a regular for loop, and one that
uses a for-each loop.

Question 12:

Convert the Employee class from the previous
question into a record class. What changes would then need to be made to the
previous question’s solution?

Question 13:

Write a record class to represent dates, where a Date object
contains three integer fields giving the month, day, and year of the date.
The canonical constructor should throw an exception if the values for the month
and day are not legal. Also include a toString() method that
prints a date in a form such as “5/27/2022”.

Question 14:

What is the purpose of the
following subroutine? What is the meaning of the value that it returns, in
terms of the value of its parameter?

static double[] sums( double[][] data ) {
    double[] answers = new double[ data.length ];
    for (int i = 0; i < data.length; i++) {
        double sum = 0;
        for (int j = 0; j < data[i].length; i++)
            sum = sum + data[i][j];
        answers[i] = sum;
    }
    return answers;
}

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