Question 0. (1 point) Write the correct ID of the section you normally attend on the cover page of this exam if you have not already done so.

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1 CSE 143 Sp04 Midterm 2 Page 1 of 10 Reference information about some standard Java library classes appears on the last pages of the test. You can tear off these pages for easier reference during the exam if you like. Question 0. (1 point) Write the correct ID of the section you normally attend on the cover page of this exam if you have not already done so. Question 1. (2 points) The implementation of our SimpleArrayList class contained the following method: private void checkposition(int pos) { if (pos < 0 pos >= size) { throw new IndexOutOfBoundsException(); Normally, if an exception can be thrown, we need to either catch the exception, or use a throws clause to declare that the method could potentially generate an exception. Yet this method, and the methods that call it, don t do either of these things (catch the exception, or declare it). Why isn t this an error? Question 2. (2 points) Two ways to automatically check for problems in a program are to use an assert statement or to write a JUnit test. When should we use assert instead of writing a unit test?

2 CSE 143 Sp04 Midterm 2 Page 2 of 10 Question 3. (2 points) The full form of an exception handler is try { // try block... catch (...) { // 0 or more catch blocks catch (...) { finally { // optional finally block Under what circumstances is the code in the finally part of the exception handler executed? Question 4. (5 points) Some of the classes in the java.io library are streams, others are not. The stream classes can be classified as source streams, sink streams, or filters (streams that transform another stream in some way). For each of the following classes, circle the correct answer to classify it is a source, sink, or filter stream, or not a stream. FileReader source sink filter not a stream BufferedReader source sink filter not a stream File source sink filter not a stream PrintWriter source sink filter not a stream StringReader source sink filter not a stream

3 CSE 143 Sp04 Midterm 2 Page 3 of 10 Question 5. (12 points) Suppose we have a HashMap containing a bunch of words and their definitions, where the words are the keys in the HashMap. For example, we might have the following data: Key newt television mosquito Entry A small toad A really effective device for wasting time A truly annoying bug Complete the definition of printdictionary on the next page so it prints the contents of the dictionary (each key followed by the associated definition) with the keys in order. For example, given the above data, the output should be mosquito A truly annoying bug newt A small toad television A really effective device for wasting time Once you have extracted the keys from the map, you will find the following fact to be useful: The Java library contains a class named java.util.collections with various static methods that operate on collections. One of these can be used to sort a List (but not a Set or Map). Its specification is: /** * Sort the items in the given list using compareto. * The elements in the List parameter will be rearranged * so they are in order. */ public static void sort(list list) Hint: The solution to this problem is fairly short if you take advantage of Collection and Map methods that manipulate or create an entire collection using a single method call or constructor. You shouldn t need lots of loops operating on collections one element at a time (although you may need one or two). Look at the reference information on the last page of the test for some ideas. Take a minute to think and outline your solution strategy before you start writing code.

4 CSE 143 Sp04 Midterm 2 Page 4 of 10 Question 5. (cont). import java.io.*; import java.util.*; /** * Print the contents of a dictionary with the keys sorted. dict the dictionary to be printed out the stream where the sorted dictionary * should be printed */ public void printdictionary(hashmap dict, PrintWriter out) {

5 CSE 143 Sp04 Midterm 2 Page 5 of 10 Question 6. (12 points) We would like to add a method to our SimpleArrayList class to remove all instances of some object from the list. More specifically, removeall(object obj) should remove all objects that are equal to obj (as determined by the equals method) from the list. (a) (6 points) Write a JUnit test that verifies that removeall properly deletes all copies of an object that appears more than once in a SimpleArrayList. If it is helpful, you can create a setup() method, but it is not required. (Obviously a full set of tests for removeall would test for other cases, but this is only a 50 minute exam and there isn t time for all of that.) import junit.framework.testcase; import java.util.*; /** Tests for removeall */ public class SimpleArrayListRemoveAllTest extends TestCase {

6 CSE 143 Sp04 Midterm 2 Page 6 of 10 Question 6. (cont) (b) (6 points) Complete the definition of method removeall(obj),below. Your code should delete items from the SimpleArrayList directly. In other words, you cannot use any other SimpleArrayList methods developed in Lecture. However, if you want, you can create or reimplement additional helper methods to use in your solution. Exception: You can use method indexof(object obj) to locate an object in the array items. Recall that this method returns -1 if obj is not found. private Object[] items; // items in this list are stored in private int size; // items[0..size-1] /** * Remove all copies of an object from the list obj All objects that are equal() to this object * will be removed */ public void removeall(object obj) {

7 CSE 143 Sp04 Midterm 2 Page 7 of 10 Question 7. (14 points) A text stream may contain lines with an arbitrary number of characters, but many output devices, like PDA or cell phone screens have a limited width. Complete the definition of method breaklines on the next page so it copies an input stream to an output stream, breaking input lines longer than the specified length into two or more output lines. Line breaks should only be made at blank spaces between words i.e., you cannot start a new line in the middle of a word. Example: Suppose the input text stream contains the following: This input stream contains some lines that are too wide to fit on some small displays. If maxwidth is 20 the output should be the following: This input stream contains some lines that are too wide to fit on some small displays Notice that no attempt is made to combine text from shorter lines with text from neighboring input lines. In other words, the method only breaks long lines into two or more output lines and copies shorter lines without change. Requirements. For full credit, you must use methods from class String (indexof, substring, etc.) to find the breaks between words and break long input lines into shorter strings. You should not search or copy character-by-character. You must use method readline() to read input lines as Strings. You should not read input character by character. When lines are broken, the space between words at the break should not be copied to the output. Your method may not contain a throws clause in its heading it should deal with exceptions appropriately by printing a short message and returning. Simplifications. To make the problem easier, you may make the following assumptions. All of the words in the input are short enough to fit on a single line of output. There is exactly one blank space between each word. There are no spaces before the first word on a line and no spaces after the last one. There are no blank lines in the input every line contains at least one word. Feel free to subdivide the solution into two or more methods if it clarifies things.

8 CSE 143 Sp04 Midterm 2 Page 8 of 10 Question 7. (cont) import java.io.*; /** * Copy a stream, breaking long input lines * into shorter output lines as needed. in The input stream. out The output stream. maxwidth Maximum number of characters that can be * written on an output line. */ public void breaklines(bufferedreader in, PrintWriter out, int maxwidth) {

9 CSE 143 Sp04 Midterm 2 Page 9 of 10 Java Reference Information Feel free to detach these pages and use them for reference as you work on the exam. class BufferedReader String readline() Return next line from input stream, or null if no more input. Can throw IOException. class PrintWriter void print(arg) void println() void println(arg) Print arg to the PrintWriter stream. The parameter can be any type Terminate the current output line and move to the beginning of the next. line Print arg, then advance to the beginning of the next line class String All of the search methods in class String return -1 if the item is not found int length() int indexof(char ch) int indexof(char ch, int start) int indexof(string str) int indexof(string str, int start) int lastindexof(char ch) int lastindexof(char ch, int start) int lastindexof(string str) int lastindexof(string str, int start) String substring(int start) String substring(int start, end) String trim() length of this string first position of ch first position of ch starting from start first position of str first position of str starting from start last position of ch last position of ch searching backward from start last position of str last position of str searching backward from start substring of this string from position start to the end substring of this string from position start to end-1 copy of this string with leading and trailing whitespace deleted

10 CSE 143 Sp04 Midterm 2 Page 10 of 10 All Collection interfaces (List, Set) and classes (ArrayList, LinkedList, HashSet, TreeSet) boolean add(object obj) boolean addall(collection other) void clear() boolean contains(object obj) Iterator iterator() boolean remove(object obj) int size() Object[] toarray() // return an array containing all the // elements in this collection In addition, all Collection classes provide a constructor that takes another Collection as a parameter and creates a new collection whose initial contents are copied from that parameter. (i.e., public ArrayList(Collection c), and similarly for the other classes.) Additional methods in List, ArrayList, LinkedList add(int position, Object obj) remove(int position) Map, HashMap, TreeMap Object put(object key, Object value) Object get(object key) Object remove(object key) Set keyset() Collection values() int size() arrays If a is a Java array, a.length is the number of elements in that array. If m is a 2-dimensional Java array, m[k] refers to row k of the array, and m[k].length is the length of that row (which is the same for all rows in a normal, rectangular array)..