Question

I Have posted my Java code below. Fix the toString, add, and remove implementations so that the following test cases work.

Note: I have removed all the unnecessary inherited List implementations. I have them to: throw new UnsupportedException(); For compilation, you could also add //TODO.

Test (Main)

List list = new SparseList<>(); list.add("0");
list.add("1");
list.add(4, "4");

will result in the following list of size 5: [0, 1, null, null, 4].

list.add(3, "Three");
will result in the following list of size 6: [0, 1, null, Three, null, 4].

However,

list.set(3, "Three);
is going to produce a list of size 5 (unchanged): [0, 1, null, Three, 4].

When removing an element from the list above, via list.remove(1)); the result should be the following list of size 4: [0, null , Three, 4]

Using the other constructor, List list = new SparseList<>(); would just result in all the null values produced by remove, get, set and toString be replaced with the specified value, e.g., [0, 1, null, null, 4]. Consider completing the implementation of your class with the default constructor only first, and then make the needed modifications.

import java.util.Collection;

import java.util.HashMap;

import java.util.Iterator;

import java.util.List;

import java.util.ListIterator;

public class SparseList implements List{

private int endIndex = 0;

private HashMap list;

public SparseList() {

list = new HashMap<>();

}

public SparseList(E[] arr) {

list = new HashMap<>();

for(int i = 0; i

list.put(i, arr[i]);

}

endIndex = arr.length - 1;

}

@Override

public boolean add(E e) {

endIndex++;

list.put(endIndex, e);

return true;

}

@Override

public void add(int index, E element) {

list.put(index, element);

}

@Override

public E remove(int index) {

return list.remove(index);

}

@Override

public E get(int index) {

return list.get(index);

}

@Override

public E set(int index, E element) {

E previous = list.get(index);

list.put(index, element);

return previous;

}

@Override

public int size() {

return endIndex + 1;

@Override

public void clear() {

list.clear();

}

@Override

public boolean isEmpty() {

return list.isEmpty();

}

@Override

public String toString() {

return list.toString();

}

}

8.4.3

Answer 1

Please try below code. If you still facing error requesting you provide the complete code. This would help us to identify and fix the problem in a faster manner.

-----------------------------------------------------------------------

import java.util.Collection;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.ListIterator;

public class SparseList implements List{

private int endIndex = 0;
private HashMap list;

public SparseList() {
this(10);
}

/*public SparseList(int lenOfArr) {
list = new HashMap<>();
for(int i = 0; i<=lenOfArr; i ++){
list.put(i, list[i]);
}
endIndex = arr.length - 1;
}*/

@Override
public boolean add(Object e) {
if (endIndex==0){
list.put(endIndex, e);
}
else {
endIndex++;
list.put(endIndex, e);
}
return true;
}

@Override
public void add(int index, Object element) {
list.put(index, element);
}

@Override
public Object remove(int index) {
return list.remove(index);
}

@Override
public Object get(int index) {
return list.get(index);
}

@Override
public Object set(int index, Object element) {
List previous = list.get(index);
list.put(index, element);
return previous;
}

@Override
public int size() {
return endIndex + 1;
}

@Override
public void clear() {
list.clear();
}

@Override
public boolean isEmpty() {
return list.isEmpty();
}

@Override
public String toString() {
return list.toString();
}

@Override
public List subList(int startIndex, int endIndex) {
// TODO
  
}

}