AP Computer Science A Unit 5 Progress Check: MCQ Part A

Consider the following method. /* missing precondition */ public void someMethod(int j, int k, String oldString) { String newString = oldString.substring(j, k); System.out.println("New string: " + newString); } Which of the following is the most appropriate precondition for someMethod so that the call to substring does not throw an exception?

/* Precondition: 0 <= j <= k <= oldString.length() */

The method addItUp(m, n) is intended to print the sum of the integers greater than or equal to m and less than or equal to n. For example, addItUp(2, 5) should return the value of 2 + 3 + 4 + 5. /* missing precondition */ public static int addItUp(int m, int n) { int sum = 0; for (int j = m; j <= n; j++) { sum += j; } return sum; }

A. /* Precondition: m <= n */

Consider the class definition below. The method levelUp is intended to increase a Superhero object's strength attribute by the parameter amount. The method does not work as intended. public class Superhero { private String name; private String secretIdentity; private int strength;

A. In line 14, levelUp should be declared as type void.

The Thing class below will contain a String attribute, a constructor, and the helper method, which will be kept internal to the class. public class Thing { /* missing code */ } Which of the following replacements for /* missing code */ is the most appropriate implementation of the class?

B. private String str; public Thing(String s) { /* implementation not shown */ } private void helper() { /* implementation not shown */ }

/* missing code */ // constructor and other methods not shown } Which of the following replacements for /* missing code */ is the most appropriate implementation of the class?

B. private int numerator; private int denominator; public double fractionToDecimal() { return (double) numerator / denominator; }

Which of the following code segments, found in a class other than Employee, could be used to correctly create an Employee object representing an employee who worked for 20 hours at a rate of $18.50 per hour?

C. I and II only

Consider the following class definition. The method appendIt is intended to take the string passed as a parameter and append it to the instance variable str. For example, if str contains "week", the call appendIt("end") should set str to "weekend". The method does not work as intended. public Class StringThing

C. Line 12 should be changed to str = str + s;

Consider the following class definition. public class Pet { private String name; private int age; public Pet(String str, int a) { name = str; age = a; } public getName() { return name; } } Which choice correctly explains why this class definition fails to compile?

C. The accessor method is missing a return type.

The statement below, which is located in a method in a different class, creates a new Person object with its attribute name initialized to "Washington". Person p = new Person("Washington"); Which of the following can be used to replace /* missing constructor */ so that the object p is correctly created?

C. public Person(String n) { name = n; }

The Employee class will contain a String attribute for an employee's name and a double attribute for the employee's salary. Which of the following is the most appropriate implementation of the class?

C. public class Employee { private String name; private double salary; // constructor and methods not shown }

String part = phrase.substring(index, index + key.length()); return part.equals(key); } Which of the following is the best precondition for index so that the method will return the appropriate result in all cases and a runtime error can be avoided?

D. 0 <= index < phrase.length() - key.length()

Consider the following class definition, which represents two scores using the instance variables score1 and score2. The method reset is intended to set to 0 any score that is less than threshold. The method does not work as intended. public class TestClass { private int score1; private int score2; } Which of the following changes can be made so that the reset method works as intended?

D. In line 18, change else if to if.

private int grade_level; private String name; private double GPA; public Student (int lvl, String nm, double gr) { grade_level = lvl; name = nm; GPA = gr; } } Which of the following object initializations will compile without error?

D. Student max = new Student (10, "Max", 3.75);

Consider the following class. public class Help { private int h; public Help(int newH) { h = newH; } public double getH() { return h; } } The getH method is intended to return the value of the instance variable h. The following code segment shows an example of creating and using a Help object. Help h1 = new Help(5); int x = h1.getH(); System.out.println(x);

D. The getH method should have a return type of int.

Consider the following class declaration. public class Student { private String name; private int age; public Student(String n, int a) { name = n; age = a; } public boolean isOlderThan5() { if (age > 5) { return true;

D. The isOlderThan5 method is missing a return statement for the case when age is less than or equal to 5.