Question

Homework Help please asap:
Exercise 7.11a Write an action method named clear for a subclass of ArrayList: The executor removes all of the values it contains.

Exercise 7.11b Write a query method named contains for a subclass of ArrayList: The executor tells whether it contains a given Object parameter. Use the equals method for the test.

Exercise 7.11c Write an action method named flip for a subclass of ArrayList: The executor swaps its first and second values, swaps its third and fourth values, swaps its fifth and six values, etc.

Answer 1

I'm having trouble on where to start in each exercise.

Answer 2

Set up each method, copy the assignment into it's method as a comment. Deal with each method in turn. Treat each as it's own problem. Decompose it until you're basically forced to write it as code to decompose it further.

Answer 3

I figured out how to do a and c (sort of) b is giving me a hard time.

Answer 4

for a and c I have
a.

public void Clear1()
{
// If we need to write this from scratch
// to destroy all elements from the aray, i could make everything start

over from the position 0.
// this would work if i have an ArrayList<String> data; I could do

data.clear
int[] elementData;

modCount++; // Thisis the NUmber of times an array List has been

structurally modified
//for loop , I set the size to 0 to start from position 0
//size = 0;
for (int i = 0; i < size; i++)
elementData[i] = null;
}

public void Clear2()
{ // I'm goingto create an empty array list with an initial capacity
ArrayList<Integer> arrlist = new ArrayList<Integer>(5);
// using the add() method to add elements in the list
arrlist.add(10);
arrlist.add(20);
arrlist.add(30);
arrlist.add(40);
//arrlist.add(50);

// printing all elements available
for (Integer number : arrlist)
{
System.out.println("Number = " + number);
}
// we need to find the size of the list
int find = arrlist.size();
System.out.println("The List consists of" + find +" elements");
arrlist.clear();
find = arrlist.size();
}

c. // I didn't know if it was ok to do this
public Exercises7_11()
{
super();

}

public void flip()
{ // Swap arr[l] and arr[a] in array arr
int temp = arr[l];
arr[l] = arr[a];
int[] list = {1, 2, 3, 4, 5};
swap(list,0, 4);
for (int num : list)
System.out.print(num + " ");
}

Answer 5

@Mathexpert

Answer 6

It took time, but I tried my school videos and came up with something. Please check if it is right. I'm trying to do well so I can become a programmer.

7.11 b
public void Contains1()
{
ArrayList<Integer> arrlist = new ArrayList<Integer>(5);
// using the add() method to add elements in the list
arrlist.add(15);
arrlist.add(25);
arrlist.add(35);
arrlist.add(45);

// list contains element 15
boolean check = arrlist.contains(15);

if (check == true)
{
System.out.println("Element 15 is in the list");
}

else
{
System.out.println("Element 15 is not in the list");
}

}

public boolean Contains2()
{ ArrayList<Integer> arrlist = new ArrayList<Integer>(5);
//arrlist.add(15);
//arrlist.add(25);
//arrlist.add(35);
//arrlist.add(45);

List list = Arrays.asList(new String[] { "A", "B", "C", "D" });
List list2 = Arrays.asList(new String[] { "A", "B", "C" });


if (list.equals(list2))
{
System.out.println("I have your elements in my list");
}

else
{
System.out.println("Sorry, I don't have your elements in my list");
}

}

Answer 7

For starters, the way I read the assignment, you're going to be extending ArrayList with a contains method. Does ArrayList have an equals method that you can use? Do the objects in the ArrayList have an equals method? Or do they have to provide a comparison method that your equals method calls?

Answer 8

I don't think so. I Have looked through my course textbook and it barely says anything about the equals method. I went to a java site and found something on the contains and clear methods. I was looking on the JavaSE7.

Answer 9

Testing primitives, ( int, char, bool, string ) is a fairly straightforward:

if( a == b )
{
// do something
}

Complex data types, like objects and collections are more difficult. An equals method would handle the comparison of your data types.

Answer 10

Thank You,
I have reread my notes and study materials. my teacher gave me an A for parts B and A. For part c, the teacher cancelled it because it was not part of the school textbook.