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Implement a class named MyArrayList that extends class the java.util. ArrayList. The class MyArrayList overrides the add(obj) method in the following way: it adds obj into the list if the object does not occur in the list or it occurs in the list only once; otherwise, if the object occurs in the list more than once, then the method does nothing.

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tonb

Answer:

import java.util.ArrayList;

import java.util.Collections;

public class MyArrayList<T> extends ArrayList<T> {

 public boolean add(T obj) {

   if (Collections.frequency(this, obj) < 2) {

     return super.add(obj);

   }

   return false;

 }

}

Explanation:

According to the requirement, an element with the same value can occur at most twice in the list.

The Collections.frequency utility is useful to count the occurrances.

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