All answers will be posted on web site, and most will be reviewed in class.

Transcription

1 Assignment 8 ArrayList Class CSC 123 Fall 2018 Notes: All homework must be submitted via . All parts of assignment must be submitted in a single with multiple attachments when required. Notes: All homework must be submitted via . All parts of assignment must be submitted in a single with multiple attachments. address is: csc123csudh@gmail.com Each program is to be submitted in a separate file with the file name being the class name with extension.java as shown below. I only need the source file. GeneralAverage.java The other homework file should be submitted with your name using the following format: RosenthalH_A8.doc, where x is the assignment number. Note: use your name, not mine All answers will be posted on web site, and most will be reviewed in class. Short Answers. 1. Declare and construct an ArrayList with an initial capacity of 20 references to Object. a. Object list(20) = new ArrayList() ; b. ArrayList list[20] = new ArrayList() ; c. ArrayList[Object] list = new ArrayList(20) ; d. ArrayList<Object> list = new ArrayList<Object>(20) ; 2. Examine the following code: ArrayList<String> list = new ArrayList<String>(10) ; list.add( "Ann" ); list.add( "Bob" ); list.add( "Eve" ); After the code has executed, what is the capacity of list? What is its size? a. 3, 3 b. 3, 10 c. 10, 3 d. 10, Examine the following code: ArrayList<String> list = new ArrayList<String>(10) ; list.add( 0, "Eve" ); What element will be at index 2 of the list? a. Eve 1

2 b. Andy c. Bart d. Carl 4. Examine the following code: Which of the following will replace the element "Carl" with "Zoltan"? a. list[2] = "Zoltan" ; b. list.set( "Zoltan", "Carl" ); c. list.add( "Zoltan", list.indexof("carl") ); d list.set( list.indexof("carl"), "Zoltan" ); 5. Examine the following code: Which of the following will change the list so that it looks like: Andy Bart Carl Doug Oscar Elmo a. list.add( 3, "Oscar" ) ; b. list.add( 4, "Oscar" ) ; c. list.set( 3, "Oscar" ) ; d. list.set( 4, "Oscar" ) ; 6. Examine the following code: Which of the following will change the list so that it looks like: 2

3 Andy Bart Doug Elmo a. list.remove( 3 ); b. list.remove( 2 ); c. list.add( 2, null ); d. list.set( list.indexof( "Carl" ), "Doug" ); 7. Examine the following code: Which of the following will change the list so that it looks like: Andy Bart Carl Doug a. list.remove( list.size() ); b. list.remove( list.size()-1 ); c. list.remove( 5 ); d. list.clear( "Elmo" ); 8. Examine the following code: Iterator iter = list. ; while( iter. ) System.out.printf( %s\n,iter. ); Fill in the blanks so that the list is printed. a. iterator() hasnext() next() b. iterator() next() nextelement() c. elements() empty() next() 3

4 d. iterator() more() get() 9. Examine the following code: while( name : ) System.out.printf( %s\n, ); Fill in the blanks so that the list is printed. a. String list name b. String iterator() next() c. int String name d. iterator() String list 10. which of the following declarations would be appropriate for a list that is expected to contain integers? a. b. ArrayList<int> list = new ArrayList<int>() ; c. ArrayList<Integer> list = new ArrayList<Integer>() ; d. ArrayList list = new ArrayList() ; 11. What is the interface implemented by a class (such as ArrayList) that implements the iterator() method? a. Iterator<E> b. Iterable 12. What is the interface implemented by an iterator object itself? a. Iterator<E> b. Iterable 13. What is true of classes that can be used with the enhanced for loop? a. All classes can use the enhanced for loop. b. Only ArrayList can use the enhanced for loop. c. Only ArrayList and arrays can use the enhanced for loop. d. Any class that implements Iterable can use the enhanced for loop. 4

5 Homework Programs Each is worth 15 points 1. OrderIntegersWithArrayList The following program can be done completely in the main method. Create a Scanner to read from a file, after requesting the name of the file. Write a program that reads in a set of integers from the file one by one and places them into an ArrayList from least to greatest. Print out the list in order from least to greatest. Hints: Check to make sure that the file is not empty. You will need to use a Wrapper class. Read the first element into the ArrayList. Read in additional integers until you reach the end of the file, inserting each number into the array list as you read it in. this is a true insertion sorting. Sample output: ArrayListReversal Write a program where main asks how many names will be entered (up to 10) and then requests the entry of those names into an ArrayList called names. Print out the list one element at a time. Then call a method reversearraylist, passing it a reference to the ArrayList names. The method reverses the order of all the elements in names. The main method should then print out names again in reverse order as shown: Original list: Jim James Louise Juan Jose Hailie Reversed List Hailie Jose Juan Louise 5

6 James Jim Finally, Ask the user to enter an index for the array and then print out that element. This should be implemented in a loop that exits if the number entered is greater than or equal to the size, or less than 0. A sample output looks like this: Please enter the number of names. It must be from 1 to 10 names:10 Please enter name for index 0 of any length: AB Please enter name for index 1 of any length: cde Please enter name for index 2 of any length: FGH Please enter name for index 3 of any length: IJK1 Please enter name for index 4 of any length: LMN09 Please enter name for index 5 of any length: PQRS Please enter name for index 6 of any length: T Please enter name for index 7 of any length: UV Please enter name for index 8 of any length: WXY Please enter name for index 9 of any length: ZZZZ Original List: AB cde FGH IJK1 LMN09 PQRS T UV WXY ZZZZ Reversed List: ZZZZ WXY UV T PQRS LMN09 IJK1 FGH cde AB 6

7 Index must be between 0 and 10, Enter a number outside of range to exit: 2 The name at index 2 is UV. Index must be between 0 and 10, Enter a number outside of range to exit: 6 The name at index 6 is IJK1. Index must be between 0 and 10, Enter a number outside of range to exit: 9 The name at index 9 is AB. Index must be between 0 and 10, Enter a number outside of range to exit: 0 The name at index 0 is ZZZZ. Index must be between 0 and 10, Enter a number outside of range to exit: 10 7