Java程序辅导

Lab 6 Exception Handling, Searching and Sorting
Student Name: ______________________________________________________
TA Initial and Checkout time: ___________________________________________
TA Comments: ______________________________________________________
Prelab: Answer the following questions before working on the lab computers.
CSci112 Fall 2011 Closed Lab Handout! Lab 6, Friday, October 7, 2011
http://www.cs.olemiss.edu/~jxue/teaching/csci112_F11/notes/lab6
Prepared by Jianxia Xue, Last Update Tuesday, October 4, 2011! 1 of 3
1. In the worst case, how many 
comparisons does binary search 
take to find a target item given a 
data pool size of n? 
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2. Does selection sort perform faster 
on a sorted vs an inversely sorted 
pool? What about bubble sort?
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3. What is the Java statement to catch 
and process an exception? Is it possible 
to process two different types of 
exceptions separately? Is it possible to 
process 4 different types of exceptions 
all at once?
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4. What is the Java statement to explicitly  
generate an exception?
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Coding Tasks
1. Debug BuggyBinarySearch.java
The given code of BuggyBinarySearch.java has two syntax errors distributed 
inside the binarySearch and the main methods. You can fixed them all together at 
one place inside the code, the eclipseʼs hint system does not provide such an option 
for you. Apply your knowledge on checked vs. unchecked Java exceptions to find a 
solution smarter than eclipseʼs suggestions.
Once the syntax errors are fixed, the driver program can be run.  It tries to search a 
user input word from a hard coded string array. It works for some entries, but not all. 
For example, it can find the word “try”, but not “sort”. The binarySearch method is a 
correct implementation. Whatʼs wrong with the code?
2. Develop Sorting.java and evaluate selection and bubble sort algorithms
      In the following bubble sort implementation: 
for (int i = n-1; i >= 0; i--)
  for (int j = 0; j <= i-1; j++)
    if (pool[j].compareTo(pool[j + 1]) > 0)
	     swap(pool, j, j + 1);
the algorithm tries to swap larger items towards the end of the unsorted set. Such 
behavior can be referred as the bubble-down sort. In this task we will make some 
variations from the given version.
a) Implement the bubble-up sort, in which smaller items will be bubbled up towards 
the beginning of the unsorted set? Run the existing driver method to validate 
your implementation of the bubbleUp method first.
b) In your bubble-up implementation, add code so every time the bubbleUp method 
is activated, one can see how many times the compareTo method was called, 
and how many times the swap method was called. 
c) Add code to the existing selection sort method to report how many times the 
methods compareTo and swap are called inside the selection sort.
d) In the main method, the existing code allow you to compare the performance 
between selection and bubble sort in execution time. With added code from part 
b) and c), you can also compare the two sorting algorithm in terms of the number 
of compares and swaps.  Run the program with 10, 100, and 1000 entries and 
check the number of compares and swaps in the selection and the bubble sorts.
e) Upgrade the main method to compare the two sorting algorithms in their best-
case and worst-case performances. Note that you can use the method of reverse 
to get the worst case arrays.
CSci112 Fall 2011 Closed Lab Handout! Lab 6, Friday, October 7, 2011
http://www.cs.olemiss.edu/~jxue/teaching/csci112_F11/notes/lab6
Prepared by Jianxia Xue, Last Update Tuesday, October 4, 2011! 2 of 3
3. (Extra Credit) Sort application
      Can you make use the sorting algorithm to generate a set from a given array? A set 
is a collection of items with no duplicate. For example, given an input array of {1,2, 4, 2, 
1, 5, 2, 4, 1, 5}, the corresponding set is {1, 2, 4, 5}. Store the resulting set in an array 
with matched size, and make your implementation polymorphable so we can apply the 
method for vocabulary generation given an array of random words.
CSci112 Fall 2011 Closed Lab Handout! Lab 6, Friday, October 7, 2011
http://www.cs.olemiss.edu/~jxue/teaching/csci112_F11/notes/lab6
Prepared by Jianxia Xue, Last Update Tuesday, October 4, 2011! 3 of 3