Chapter 24, Problem 24.1PE

(Implement set operations in MyList) The implementations of the methods addAll, removeAll, retainAll, toArray(), and toArray(T[]) are omitted in the MyList interface. Implement these methods. Test your new MyList class using the code at liveexample.pearsoncmg.com/test/ Exercise24_01Test.txt.

Program Plan Intro

MyList

Program plan:

• Import required packages.
• Declare the main class named “Main”.
  • Give the main method “public static void main ()”.
    • Declare a default constructor and data members.
    • Prompt the user to get the input.
    • Print the value of list1 and list2.
    • Print the result by calling the function “addAll()”.
    • Print the value of list1 and list2.
    • Print the result by calling the method “removeAll()”.
    • Print the value of list1 and list2.
    • Print the result by calling the method “retainAll()”.
    • Print the value of list1 and list2.
    • Print the result by calling the method “containsAll()”.
  • Includes an interface “MyList”
    • Define a method to add a new element at the specified index in the list.
    • Define a method to return the element from this list at the specified index 
    • Define a method to return the index of the first matching element in this list.
    • Define a method to return the index of the last matching element in this list
    • Define a method to remove the element at the specified position in this list
    • Define a method to replace the element at the specified position in this list
    • Define a method to add a new element at the end of this list
    • Define a method to return true if this list contains no elements
    • Define a method to remove the first occurrence of the element e from this list
    • Define a method to check whether the elements are present or not
    • Define a method to add the elements in otherList to this list.
    • Define a method to retains the elements in this list that are also in otherList
  • Define a class “MyArrayList”.
    • Declare a variable “sum” and assign 0 to it.
    • Declare data members and default constructor.
    • Create a list from an array of object.
    • Define a method to add a new element at the specified index 
    • Define a method to create a larger array which is double the current size.
    • Define a method to clear the list.
    • Define a method to return true if the list contains the element.
    • Define a method to return the element at the specified index.
    • Define a method to trim the capacity to current size.
    • Define a method to return the number of element in the list.

Program Description Answer

The below program includes the methods addAll(), removeAll(), retainAll(), toArray(), and toArray(T[]) which were omitted in the MyList interface.

Explanation of Solution

Program:

//import required packages

import java.util.*;

//class definition

public class Exercise24_01 {

//define main method

public static void main(String[] args) {

new Exercise24_01();

}

//default constructor

public Exercise24_01() {

Scanner input = new Scanner(System.in);

//data members

String[] name1 = new String[5];

String[] name2 = new String[5];

String[] name3 = new String[2];

//prompt user to get the input

System.out.print("Enter five strings for array name1 separated by space: ");

for (int i = 0; i < 5; i++) {

name1[i] = input.next();

}

//prompt the user to get the input

System.out.print("Enter five strings for array name2 separated by space: ");

for (int i = 0; i < 5; i++) {

name2[i] = input.next();

}

//prompt user to get the input

System.out.print("Enter two strings for array name3 separated by space: ");

for (int i = 0; i < 2; i++) {

name3[i] = input.next();

}

MyList<String> list1 = new MyArrayList<>(name1);   

MyList<String> list2 = new MyArrayList<>(name2); 

//print the value of list1

System.out.println("list1:" + list1);

//print the value of list2

System.out.println("list2:" + list2);

//calling addAll function

list1.addAll(list2);

//print the result

System.out.println("After addAll:" + list1 + "\n");

list1 = new MyArrayList<>(name1);

list2 = new MyArrayList<>(name2); 

//print the value of list1

System.out.println("list1:" + list1);

//print the value of list2

System.out.println("list2:" + list2);

//calling removeAll function

list1.removeAll(list2);

//print the result

System.out.println("After removeAll:" + list1 + "\n");

list1 = new MyArrayList<>(name1);

list2 = new MyArrayList<>(name2); 

//print the value of list1

System.out.println("list1:" + list1);

//print the value of list2

System.out.println("list2:" + list2);

//calling the retainAll function

list1.retainAll(list2);

//print the result

System.out.println("After retainAll:" + list1 + "\n");

list1 = new MyArrayList<>(name1);

list2 = new MyArrayList<>(name2); 

//print the value of list1

System.out.println("list1:" + list1);

//print the value of list2

System.out.println("list2:" + list2);

//calling the retainAll function

list1.retainAll(list2);

//print the result

System.out.println("list1 contains all list2? " + list1.containsAll(list2) + "\n");

list1 = new MyArrayList<>(name1);

list2 = new MyArrayList<>(name3);

//print the value of list1

System.out.println("list1:" + list1);

//print the value of list2

System.out.println("list2:" + list2);

//print the result

System.out.println("list1 contains all list2? " + list1.containsAll(list2) + "\n");

Object[] name4 = list1.toArray();

//print the result

System.out.print("name4: ");

for (Object e: name4) {

System.out.print(e + " ");

}

String[] name5 = new String[list1.size()];

String[] name6 = list1.toArray(name5);

//print the result

System.out.print("\nname6: ");

for (Object e: name6) {

System.out.print(e + " ");

}

}

//includes the interface

public interface MyList<E> extends java.util.Collection<E> {

/* Add a new element at the specified index in this list */

public void add(int index, E e);

/*Return the element from this list at the specified index */

public E get(int index);

/*Return the index of the first matching element in this list. Return -1 if no match. */

public int indexOf(Object e);

/*Return the index of the last matching element in this list,  Return -1 if no match. */

public int lastIndexOf(E e);

/* Remove the element at the specified position in this list, Shift any subsequent elements to the left. Return the element that was removed from the list. */

public E remove(int index);

/* Replace the element at the specified position in this list, with the specified element and returns the new set. */

public E set(int index, E e);

@Override /* Add a new element at the end of this list */

public default boolean add(E e) {

add(size(), e);

return true;

}

@Override /* Return true if this list contains no elements */

public default boolean isEmpty() {

return size() == 0;

}

@Override /* Remove the first occurrence of the element e from this list. Shift any subsequent elements to the left, Return true if the element is removed. */

public default boolean remove(Object e) {

if (indexOf(e) >= 0) {

remove(indexOf(e));

return true;

}

else

return false;

}

@Override

/*method to check whether the elements are present or not */

public default boolean containsAll(Collection<?> c) {

for (Object e: c)

if (!this.contains(e))

return false;

return true;

}

/* Adds the elements in otherList to this list.

Returns true if this list changed as a result of the call */

@Override

public default boolean addAll(Collection<? extends E> c) {

for (E e: c)

this.add(e);

return c.size() > 0;

}

/* Removes all the elements in otherList from this list Returns true if this list changed as a result of the call */

@Override

public default boolean removeAll(Collection<?> c) {

boolean changed = false;

for (Object e: c) {

if (remove(e))

changed = true;

}

return changed;

}  

/* Retains the elements in this list that are also in otherList, Returns true if this list changed as a result of the call */

@Override

public default boolean retainAll(Collection<?> c) {

boolean changed = false;

for (int i = 0; i < this.size(); ) {

if (!c.contains(this.get(i))) {

this.remove(get(i));

changed = true;

}

else

i++;

}

return changed;

}

@Override

public default Object[] toArray() {

// Left as an exercise

Object[] result = new Object[size()];

for (int i = 0; i < size(); i++) {

result[i] = this.get(i);

}

//return statement

return result;

}

@Override

public default <T> T[] toArray(T[] a) {

// Left as an exercise

for (int i = 0; i < size(); i++) {

a[i] = (T)this.get(i);

}

//return statement

return a;

}

}

//class definition

public class MyArrayList<E> implements MyList<E> {

//data members

public static final int INITIAL_CAPACITY = 16;

private E[] data = (E[])new Object[INITIAL_CAPACITY];

private int size = 0;

// Create an empty list

public MyArrayList() {

}

//Create a list from an array of objects 

public MyArrayList(E[] objects) {

for (int i = 0; i < objects.length; i++)

add(objects[i]);

}

@Override /* Add a new element at the specified index */

public void add(int index, E e) {   

ensureCapacity();

/* Move the elements to the right after the specified index */

for (int i = size - 1; i >= index; i--)

data[i + 1] = data[i];

// Insert new element to data[index]

data[index] = e;

// Increase size by 1

size++;

}

/*Create a new larger array, double the current size + 1 */

private void ensureCapacity() {

if (size >= data.length) {

E[] newData = (E[])(new Object[size * 2 + 1]);

System.arraycopy(data, 0, newData, 0, size);

data = newData;

}

}

@Override // Clear the list

public void clear() {

data = (E[])new Object[INITIAL_CAPACITY];

size = 0;

}

@Override /*Return true if this list contains the element */

public boolean contains(Object e) {

for (int i = 0; i < size; i++)

if (e.equals(data[i])) return true;

return false;

}

@Override /*Return the element at the specified index */

public E get(int index) {

checkIndex(index);

return data[index];

}

private void checkIndex(int index) {

if (index < 0 || index >= size)

throw new IndexOutOfBoundsException

("Index: " + index + ", Size: " + size);

}

@Override /*Return the index of the first matching element in this list. Return -1 if no match. */

public int indexOf(Object e) {

for (int i = 0; i < size; i++)

if (e.equals(data[i])) return i;

return -1;

}

@Override /*Return the index of the last matching element in this list. Return -1 if no match. */

public int lastIndexOf(E e) {

for (int i = size - 1; i >= 0; i--)

if (e.equals(data[i])) return i;

return -1;

}

@Override /* Remove the element at the specified position in this list. Shift any subsequent elements to the left. Return the element that was removed from the list. */

public E remove(int index) {

checkIndex(index);

E e = data[index];

// Shift data to the left

for (int j = index; j < size - 1; j++)

data[j] = data[j + 1];

data[size - 1] = null;

// Decrement size

size--;

return e;

}

@Override /*Replace the element at the specified position in this list with the specified element. */

public E set(int index, E e) {

checkIndex(index);

E old = data[index];

data[index] = e;

return old;

}

@Override

public String toString() {

StringBuilder result = new StringBuilder("[");

for (int i = 0; i < size; i++) {

result.append(data[i]);

if (i < size - 1) result.append(", ");

}

return result.toString() + "]";

}

// Trims the capacity to current size 

public void trimToSize() {

if (size != data.length) { 

E[] newData = (E[])(new Object[size]);

System.arraycopy(data, 0, newData, 0, size);

data = newData;

} // If size == capacity, no need to trim

}

@Override /*Override iterator() defined in Iterable */

public java.util.Iterator<E> iterator() {

return new ArrayListIterator();

}

private class ArrayListIterator 

implements java.util.Iterator<E> {

// Current index 

private int current = 0; 

@Override

public boolean hasNext() {

return (current < size);

}

@Override

public E next() {

return data[current++];

}

@Override

public void remove() {

MyArrayList.this.remove(current);

}

}

@Override /* Return the number of elements in this list */

public int size() {

return size;

}

}

}

Sample Output

Enter five strings for array name1 separated by space: tom george peter jean jane

Enter five strings for array name2 separated by space: tom george michael michelle daniel

Enter two strings for array name3 separated by space: tom peter

list1:[tom, george, peter, jean, jane]

list2:[tom, george, michael, michelle, daniel]

After addAll:[tom, george, peter, jean, jane, tom, george, michael, michelle, daniel]

list1:[tom, george, peter, jean, jane]

list2:[tom, george, michael, michelle, daniel]

After removeAll:[peter, jean, jane]

list1:[tom, george, peter, jean, jane]

list2:[tom, george, michael, michelle, daniel]

After retainAll:[tom, george]

list1:[tom, george, peter, jean, jane]

list2:[tom, george, michael, michelle, daniel]

list1 contains all list2? false

list1:[tom, george, peter, jean, jane]

list2:[tom, peter]

list1 contains all list2? true

name4: tom george peter jean jane 

name6: tom george peter jean jane