1. Which of the following is the correct expression of character 4? a. 4 b. "4" c. '\0004' d. '4'

Transcription

1 Practice questions: 1. Which of the following is the correct expression of character 4? a. 4 b. "4" c. '\0004' d. '4' 2. Will System.out.println((char)4) display 4? a. Yes b. No 3. The expression "Java " evaluates to. a. Java123 b. Java6 c. Java 123 d. java 123 e. Illegal expression 4. The statement System.out.printf("%10s", ) outputs. (Note: * represents a space) a **** b ***** c ***** d. **** Which of the following is a possible output for (int)(51 * Math.random())? a. 0 b. 51 c. 100 d You should fill in the blank in the following code with. public class Test { public static void main(string[] args) { System.out.print("The grade is "); printgrade(78.5); System.out.print("The grade is "); printgrade(59.5); public static printgrade(double score) { if (score >= 90.0) { System.out.println('A');

2 else if (score >= 80.0) { System.out.println('B'); else if (score >= 70.0) { System.out.println('C'); else if (score >= 60.0) { System.out.println('D'); else { System.out.println('F'); a. int b. double c. boolean d. char e. void 7. A variable defined inside a method is referred to as. a. a global variable b. a method variable c. a block variable d. a local variable 8. What is k after the following block executes? { int k = 2; nprint("a message", k); System.out.println(k); a. 0 b. 1 c. 2 d. k is not defined outside the block. So, the program has a compile error 9. You can define two methods in the same class with the same name and parameter list. a. true b. false 10. If you declare an array double[] list = {3.4, 2.0, 3.5, 5.5, list[1] is. a. 3.4

3 b. 2.0 c. 3.5 d. 5.5 e. undefined 11. What is the output of the following code? double[] mylist = {1, 5, 5, 5, 5, 1; double max = mylist[0]; int indexofmax = 0; for (int i = 1; i < mylist.length; i++) { if (mylist[i] > max) { max = mylist[i]; indexofmax = i; System.out.println(indexOfMax); a. 0 b. 1 c. 2 d. 3 e Analyze the following code: public class Test { public static void main(string[] args) { double[] x = {2.5, 3, 4; for (double value: x) System.out.print(value + " "); a. The program displays 2.5, 3, 4 b. The program displays c. The program displays d. The program displays 2.5, e. The program has a syntax error because value is undefined. 13. Variables that are shared by every instances of a class are. a. public variables b. private variables c. instance variables d. static variables 14. What is the printout of the second println statement in the main method? public class Foo {

4 int i; static int s; public static void main(string[] args) { Foo f1 = new Foo(); System.out.println("f1.i is " + f1.i + " f1.s is " + f1.s); Foo f2 = new Foo(); System.out.println("f2.i is " + f2.i + " f2.s is " + f2.s); Foo f3 = new Foo(); System.out.println("f3.i is " + f3.i + " f3.s is " + f3.s); public Foo() { i++; s++; a. f2.i is 1 f2.s is 1 b. f2.i is 1 f2.s is 2 c. f2.i is 2 f2.s is 2 d. f2.i is 2 f2.s is You can declare two variables with the same name in. a. a method one as a formal parameter and the other as a local variable b. a block c. two nested blocks in a method (two nested blocks means one being inside the other) d. different methods in a class 16. Which of the following can be placed in the blank line in the following code? public class Test { private int id; public void m1() {.id = 45; a. this b. Test 17. Suppose you create a class Square to be a subclass of GeometricObject. Analyze the following code: class Square extends GeometricObject { double length;

5 Square(double length) { GeometricObject(length); a. The program compiles fine, but you cannot create an instance of Square because the constructor does not specify the length of the Square. b. The program has a compile error because you attempted to invoke the GeometricObject class's constructor illegally. c. The program compiles fine, but it has a runtime error because of invoking the Square class's constructor illegally. 18. Following the example of the Circle class in Section 9.2, design a class named Rectangle to represent a rectangle. The class contains: Two double data fields named width and height that specify the width and height of the rectangle. The default values are 1 for both width and height. A no-arg constructor that creates a default rectangle. A constructor that creates a rectangle with the specified width and height. A method named getarea() that returns the area of this rectangle. A method named getperimeter() that returns the perimeter. Write a test program that creates two Rectangle objects one with width 4 and height 40 and the other with width 3.5 and height Display the width, height, area, and perimeter of each rectangle in this order. 19. Design a class named Fan to represent a fan. The class contains: Three constants named SLOW, MEDIUM, and FAST with the values 1, 2, and 3 to denote the fan speed. A private int data field named speed that specifies the speed of the fan (the default is SLOW). A private boolean data field named on that specifies whether the fan is on (the default is false). A private double data field named radius that specifies the radius of the fan (the default is 5). A string data field named color that specifies the color of the fan (the default is blue). The getter and setter methods for all four data fields. A no-arg constructor that creates a default fan. A method named tostring() that returns a string description for the fan. If the fan is on, the method returns the fan speed, color, and radius in one combined string. If the fan is not on, the method returns the fan color and radius along with the string fan is off in one combined string. Write a test program that creates two Fan objects. Assign maximum speed, radius 10, color yellow, and turn it on to the first object. Assign medium speed, radius 5, color blue, and turn it off to the second object. Display the objects by invoking their tostring method.

6 20. Design a class named Person and its two subclasses named Student and Employee. Make Faculty and Staff subclasses of Employee. A person has a name, address, phone number, and address. A student has a class status (freshman, sophomore, junior, or senior). Define the status as a constant. An employee has an office, salary. A faculty member has a rank. A staff member has a title. Override the tostring method in each class to display the class name, the person s name, and the rest of the information. Draw the UML diagram for the classes and implement them. Write a test program that creates a Person, Student, Employee, Faculty, and Staff, and invokes their tostring() methods. 21. Write a program that prompts the user to enter an integer between 0 and 15 and displays its corresponding hex number. Here are some sample runs: Enter a decimal value (0 to 15): 11 The hex value is B Enter a decimal value (0 to 15): 5 The hex value is 5 Enter a decimal value (0 to 15): is an invalid input 22. Write a method with the following header to display an integer in reverse order: public static void reverse(int number) For example, reverse(3456) displays Write a test program that prompts the user to enter an integer and displays its reversal. Assume the user input is always a positive integer. 23. Write a program that reads an unspecified number of scores and determines how many scores are above or equal to the average and how many scores are below the average. Enter a negative number to signify the end of the input. Assume that the maximum number of scores is 100.