CMPS 134 Fall 2018
Preview for Test #2

• Know everything that you were supposed to know for Test #1.
• Expect a question in which you are given a set of terms having to do with Java programming and a list of statements each of which has one or two blanks to be filled in from terms in the given set. Example:
  1. A(n) _____ method is one that returns information about the state of a(n) _____.
  The answers are observer and object.
• Expect a problem in which you are given the code of an "instance" class (i.e., one from which it is intended that objects will be created) and you are asked to write a code segment that might appear in a client program, such as one that creates an object of that class (or perhaps two of them) and carries out some specific task with it/them.

  Example: Develop the main() method of an application program that creates two TossableCoin objects and repeatedly tosses both of them until exactly one of them is showing heads. Then report how many tosses were made to reach that situation.

• Expect a problem in which a program, or code segment, is given and you are asked to show what output it produces. (Or a functional method is given, with parameter value(s) specified, and you are asked to indicate what value the method returns.) Don't be surprised if the code involves the creation and/or manipulation of objects (e.g. Strings, an array). Also expect to see if-else statement(s) and/or loop(s). If a loop is involved, the problem might ask you to show the values of one or more variables at specific moments in time (e.g., at the end of each loop iteration).

  Example 1: Tell what value is returned by the method call mystery(100), where the relevant method is as follows:

  public static int mystery(int m) { int low = 0, high = m+1; while (low + 1 != high) { int mid = (low + high) / 2; if (mid * mid <= m) { low = mid; } else { high = mid; } } return low; }

  Also show the values of local variables low and high at the end of each loop iteration.

  Example 2: Tell what value is returned by the method call stringSwap("abcdefghi"), where the relevant method is as follows:

  public static int stringSwap(String s) { int k = s.length() / 2; return s.substring(k) + s.substring(0,k); }

  Example 3: Show the contents of array a[] upon completion of execution of this code segment:

  int[] a = new int[6]; a[0] = 1; for (int i=1; i != a.length; i=i+1) { a[i] = 2 * a[i-1]; }

• Expect a problem in which you are given a Java instance class and are asked to modify a method, or add a new method, so that the method behaves in a specified way. Another possibility is to write a method that carries out some operation upon a String object (or a pair thereof).

  Example 1: You are given the WrapAroundCounter class and are asked to add a new method as follows:

  /* Increments this counter by the specified amount (k), wrapping ** around if appropriate. For example, if this counter's maximum value ** is 12 and its current value is 8, then incrementing by 7 results in ** its value being 2. */ public void increment(int k) { ... }

  Example 2: Supply a body for the following method:

  /* Returns the distance, within the given String (s), between the ** first two occurrences of the given character (ch). If there are ** fewer than two occurrences of ch in s, -1 is returned. */ public static int distanceBetween(String s, char ch) { ... }