380. Insert Delete GetRandom O(1)

import java.util.ArrayList;
import java.util.List;
import java.util.Random;

//380. Insert Delete GetRandom O(1)
//Design a data structure that supports all following operations in average O(1) time.
//
//insert(val): Inserts an item val to the set if not already present.
//remove(val): Removes an item val from the set if present.
//getRandom: Returns a random element from current set of elements. Each element must have the same probability of being returned.
//Example:
//
//// Init an empty set.
//RandomizedSet randomSet = new RandomizedSet();
//
//// Inserts 1 to the set. Returns true as 1 was inserted successfully.
//randomSet.insert(1);
//
//// Returns false as 2 does not exist in the set.
//randomSet.remove(2);
//
//// Inserts 2 to the set, returns true. Set now contains [1,2].
//randomSet.insert(2);
//
//// getRandom should return either 1 or 2 randomly.
//randomSet.getRandom();
//
//// Removes 1 from the set, returns true. Set now contains [2].
//randomSet.remove(1);
//
//// 2 was already in the set, so return false.
//randomSet.insert(2);
//
//// Since 2 is the only number in the set, getRandom always return 2.
//randomSet.getRandom();

public class InsertDeleteGetRandom380 {
	/** Initialize your data structure here. */
	List<Integer> list ;
    public InsertDeleteGetRandom380() {
    	list = new ArrayList<Integer>();
    }
    
    /** Inserts a value to the set. Returns true if the set did not already contain the specified element. */
    public boolean insert(int val) {
    	if(list.contains(val)){
    		return false;
    	}
    	else{
    		list.add(val);
    		return true;
    	}
    }
    
    /** Removes a value from the set. Returns true if the set contained the specified element. */
    public boolean remove(int val) {
    	if(list.contains(val)){
    		list.remove((Integer)val);
    		return true;
    	}
    	else{
    		return false;
    	}
    }
    
    /** Get a random element from the set. */
    public int getRandom() {
    	Random random = new Random();
    	int i = random.nextInt(list.size());
    	return list.get(i);
    }
}