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1. Identify the variables that are both valid in Java and follow its naming conventions: NumCheques typeoffile 2ndCard cardOne 2. Which of the following are primitive types? int char String Board boolean 3. What is the assignment operator in Java? Answer: = 4. Use 2 lines to declare and initialize a double value called 'weight' to 70.55. Then do it on one line. Answer: 1) double weight; weight = 70.55; 2) double weight = 70.55; 5. What is the value of arbitraryNumber at the end of the following code? int arbitraryNumber = 4; arbitraryNumber++; arbitraryNumber *= 2; arbitraryNumber % 6; arbitraryNumber = arbitraryNumber/3; Answer: 3 6. What are the values of steps in each of the 2 cases below? double steps; steps = 7/2; Answer: 3.0 (changed on Feb 20th, 12:20pm) steps = 7.0/2; Answer: 3.5 7. What is the value of arbitraryString at the end of the following code? String s1 = “Use Google”; String s2 = “Code sensibly”; String s3 = s1.substring(4,6); String arbitraryString = s3 + s2.substring(4,9) + “ ” + s3; Answer: Go sens Go 8. What is the value of arbitraryString at the end of the following code? String arbitraryString = "ABC"; arbitraryString += arbitraryString.charAt(2); arbitraryString.toLowerCase(); Answer: abcc 9. What will the following code print? Why? char first = ‘a’; char second = ‘b’; System.out.println((char) (first + second)); Answer: 195 10. What will the following lines of code print? String arbitraryString = "\"Hi\" how\nare you?" System.out.print(arbitraryString); Answer: “Hi” how are you? 11. What will the following lines of code print if the user enters … ‘ Hello How are you? ’ … when prompted for input? Scanner in = new Scanner(System.in); String first = in.next(); String second = in.next(); String third = in.nextLine(); System.out.print(first + second + third); Answer: ‘HelloHow are you? ’ 12. Assume isGameOver is a boolean variable that has been initialized and declared. What is a better way to write the following lines of code? if(isGameOver) { } else { System.out.println("Take your turn."); } Answer: if (!isGameOver) { System.out.println(“Take your turn.”); } 13. When is it appropriate to use .equals() instead of ==? Answer: .equals() for when you’re comparing objects, and == for comparing primitive types (int, char, boolean, etc) 14. What is the output of the following lines of code? String one = "Hello"; String two = "hello"; System.out.println(one.equals(two)); System.out.println(one.equalsIgnoreCase(two)); System.out.println(!one.equalsIgnoreCase(two)); System.out.println(one.equals(two) && one.equalsIgnoreCase(two)); System.out.println(one.equals(two) || one.equalsIgnoreCase(two)); Answer: false true false false true 15. What is the output of the following lines of code? for (int num = 2; num <= 7; num++) { if (num % 2 == 0) { System.out.println(“A”); } else if (3 <= num && num <= 5) { System.out.println(“B”); } else if (num % 3 == 0) { System.out.println(“C”); } else { System.out.println(“D”); } } Answer: A B A B A D 16. What does the following code print? boolean a = true; boolean b = false; boolean c = true; System.out.println((a&&b)||(!b&&c)); System.out.println(((a&&b)||(!b&&c)) == b); Answer: true false 17. When is it best to use a for loop? What about a while loop? Answer: for loop whenever you have an idea of how many iterations you want (either explicit, or implicit); use a while for any other case 18a. How many times is Hello printed? for(int i = 0; i < 5; i++) { System.out.print("Hello"); } Answer: 5 18b. What about in the following loop? for(int i = 100; i < 105; i++) { System.out.print("Hello"); } Answer: 5 19. What would the following code do? Assume myString is initialized and declared. int position = myString.indexOf(“ ”); while (position != -1) { String firstHalf = myString.substring(0, position); String secondHalf = myString.substring(position + 1); myString = firstHalf + secondHalf; position = myString.indexOf(“ ”); } Answer: remove all spaces, i.e. Hello how are you Hellohow are you Hellohoware you Hellohowareyou 20. Suppose we want to continually prompt the user for input until we receive some particular String. What type of loop should we use? Answer: while loop; e.g. if the string is “quit”, we could say: String in = input.nextLine(); while (!in.equals(“quit”)) { in = input.nextLine(); } // will stop asking for input when in.equals(“quit”) is true 21. What does the following code do? Assume number is initialized and declared. for (int i = 2; i <= number; i = i * 2) { System.out.println(i); } Answer: prints all powers of 2 up to number 22. What does the following code do? Assume number is initialized and declared. for(int i = 1; i <= number; i++) { if(number%i == 0) { System.out.println(i); } } Answer: prints all factors of number 23. What does the following code do? Scanner in = new Scanner(System.in); String input = “”; while (input.indexOf(‘!’) == -1) { input += in.next(); } System.out.println(input); Answer: print out the user’s input without spaces or whitespace until the input includes an “!” 24. What does instantiating an object mean? Answer: creating an instance of a class. For example, “graph = new Board(5, 5);” is instantiating a Board object 25. Suppose we have an object called a GameBoy that can be instantiated without any parameters. Write code to create a GameBoy object referenced by the variable myGameBoy. Answer: GameBoy myGameBoy = new GameBoy(); 26. What is the function of an instance variable? Answer: an instance variable contains some information specific to the object. E.g. a Person object might have instance variables called age, height, and weight 27. Which methods in a class have access to the instance variables within that class? Answer: ALL methods 28. What would we type to create an instance variable called columns and to initialize it to 5? Answer: int columns = 5; 29. What does it mean for a method to be void? Answer: requires no return value 30. What is the return type of the method next() from the Scanner class? Answer: String 31. What does the following code perform? Scanner in = new Scanner(System.in); String newString = in.next().toUpperCase(); System.out.println(newString); Answer: transforms the input string into uppercase (e.g. HeLlo how arE yOu -> HELLO) 32. True or false: Void methods must always have return statements. Answer: false; void methods don’t return anything 33. What does ‘this’ refer to when it is used in a method? Answer: current object 34. What happens if we run the following lines of code? if(3 < 4) { int a = 8; } System.out.println(a); Answer: 8 35. Consider the following method signature. Is position a parameter or an argument? public char charAt(int position) Answer: parameter 36. Consider the following line of code (Assume position is an int and myString is a String, both of which have been initialized and declared). Is position a parameter or an argument? char c = myString.charAt(position); Answer: argument 37. What are the pre and post conditions for the charAt(int index) method of the String class? Answer: Pre: 0 <= index < this.length(); Post: return character of this at position index 38. What is the difference between the visibility modifiers 'public' and 'private'? Answer: public means that the variable or method can be seen by anyone (from inside the class or outside); private means that the variable or method can ONLY be accessed within its own class 39. Is the method getRows() of the Board class an accessor method, mutator method, or neither? Answer: accessor 40. Is the method makePayment(int payment) of the CreditCard class an accessor method, mutator method, or neither? Answer: neither. As a general guideline, accessor methods usually start with “get” and mutator methods start with “set” 41. What is the output of the following lines of code? String originalString = “high”; String s1 = originalString.substring(0,2); String s2 = “hi”; System.out.println(s1 == s2); System.out.println(s1.equals(s2)); Answer: false true