These questions relate to next questions I\'ll post separately (they are confuse

Question

These questions relate to next questions I'll post separately (they are confuse me) Please explain. Thank you very much.

Self-Check Exercise

1. What does the following code fragment do?

ArrayList<Double> myList = new ArrayList<Double>();

myList.add(3.456);

myList.add(5.0);

double result = myList.get(0) + myList.get(1);

System.out.println("Result is " + result);

2. Trace the execution of the following:

int[] anArray = {0, 1, 2, 3, 4, 5, 6, 7};

for (int i = 3; i < anArray.length – 1; i++)

anArray[i + 1] = anArray[i];

and the following:

int[] anArray = {0, 1, 2, 3, 4, 5, 6, 7};

for (int i = anArray.length – 1; i > 3; i--)

anArray[i] = anArray[i – 1];

What are the contents of anArray after the execution of each loop?

Programming Exercise

Try to think about how to implement KWArrayList class. Please implement the following constructor and methods:

public KWArrayList()

public boolean add(E anEntry)

public E get(int index) { public E set(int index, E newValue)

public E remove(int index)

private void reallocate()

public int size()

public int indexOf(Object item)

Study the code for ArrayList implementation (enclosed in the folder) and work on the following exercise

1. Provide a constructor for class KWArrayList that accepts an int argument that represents the initial array capacity.

Use this instead of INITIAL_CAPACITY.

2. Implement the indexOf method of the KWArrayList class.

3.Write statements to remove the middle object from a KWArrayList and place it at the end.

/** Removes middle object and re-inserts it at the end @return E object removed and re-inserted */

public E removeMiddleInsertEnd()

{

}

4. Please define a tester class to verify your code.

Explanation / Answer

1. What does the following code fragment do?
ArrayList<Double> myList = new ArrayList<Double>();   //Creates an empty array list named myList.
myList.add(3.456);   //Appends a value 3.456 to the myList at the end.
myList.add(5.0);   //Appends a value 5.0 to the myList at the end.
double result = myList.get(0) + myList.get(1);   //Adds both the above values (3.456 + 5.0 = 8.456), and stores the result in result.
System.out.println("Result is " + result);   //Prints the statement: Result is 8.456

2. Trace the execution of the following:
int[] anArray = {0, 1, 2, 3, 4, 5, 6, 7};   //Creates an integer array named anArray.
for (int i = 3; i < anArray.length – 1; i++)   //Starting from i value 3 up to anArray.length-2 i.e., 6.
anArray[i + 1] = anArray[i];       //The values will be moved to the right.
So, now the contents are:
{0, 1, 2, 3, 3, 3, 3, 3}.
Note that, the first time the statement is executed for i value 3, the statement is:
anArray[4] = anArray[3];   //So, this statements copies the value from index 3 to index 4.
So, 3 will be copied to index 4.
Next the value in index 4 will be copied to index 5, and all this will simply propagate 3 throughout the array.

and the following:
int[] anArray = {0, 1, 2, 3, 4, 5, 6, 7};   //Creates an integer array named anArray.
for (int i = anArray.length – 1; i > 3; i--)   //Starting from anArray.length-1 i.e., 7 down to 4.
anArray[i] = anArray[i – 1];   //The values will be moved to the right.
So, now the contents are:
{0, 1, 2, 3, 3, 4, 5, 6}.
Note that, the first time the statement is executed for i value 7, the statement is:
anArray[7] = anArray[6];   //So, this statement copies the value 6 to index 7.
Next time it copies, 5 to index 6, and so on, till
anArray[4] = anArray[3];

What are the contents of anArray after the execution of each loop?

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