import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;


public class CollectionsInJava {
	public static void main(String[] args) {
		// 1. Reverse an ArrayList without using inbuilt method
		// 2. Find Duplicate Elements in a List 
		// 3. Alphabetical Order and Ascending Order (Done in ArrayList)
		// 4. Merge Two Lists and Remove Duplicates
		// 5. Removing Even Nos from the List
		// 6. Array to List, List to Array
		ArrayList<String> names = new ArrayList<>(Arrays.asList("Abinaya", "Ramya", "Gowri", "Swetha",  "Sugi", "Anusuya", "Moogambigai","Jasima","Aysha"));
		ArrayList<Integer> al2 = new ArrayList<>(Arrays.asList(100,90,30,20,60,40));
		
		ArrayList<Integer> al =  insertValuesIntoAL();
		System.out.println("Before Reversing ArrayList="+ al);
		System.out.println("Reversed ArrayList="+ reverseArrayList(al));
		
		System.out.println("Duplicates in ArrayList="+findDuplicates(al));
		
		System.out.println("Before Order = "+names);
		Collections.sort(names);
		System.out.println("After Alphabetical Order = " + names);
		Collections.sort(al);
		System.out.println("Ascending Order = "+ al);
		
		System.out.println("List -1 = "+al);
		System.out.println("List -2 = "+al2);
		System.out.println("After Merging and Removing Duplicates="+mergeTwoLists(al,al2));
		System.out.println("After Removing Even Nos fromt the List-1 = "+removeEvenNos(al));
		
		arrayToListViceVersa(al,new int[] {11,12,13,14,15}); //Sending ArrayList and anonymous array
	}
	
	// 1. Reverse an ArrayList without using inbuilt method
	private static ArrayList<Integer> reverseArrayList(ArrayList<Integer> al) {
		int n=al.size();
		int j=n-1, mid=n/2;
		for (int i=0; i<mid; i++) {
			int temp = al.get(i);
			al.set(i, al.get(j));
			al.set(j--, temp);
		}
		return al;
	}
	
	// 2. Find Duplicate Elements in a List 
	private static ArrayList<Integer> findDuplicates(ArrayList<Integer> al) {
		HashSet<Integer> hs = new HashSet<>();
		ArrayList<Integer> arl = new ArrayList<>();
		for (int ele:al) {
			if (!hs.add(ele)) arl.add(ele);
		}
		return arl;
	}
	
	//4. Merge Two Lists into one and Remove Duplicates
	private static HashSet<Integer> mergeTwoLists(ArrayList<Integer> arl1,ArrayList<Integer> arl2) {
		ArrayList<Integer> resAl = new ArrayList<>();
		HashSet<Integer> hs = new HashSet<>();
		hs.addAll(arl1);
		hs.addAll(arl2);
		return hs;
	}
	
	// 5. Removing Even Nos from the List
	private static ArrayList<Integer> removeEvenNos(ArrayList<Integer> al) {
		ArrayList<Integer> res = new ArrayList<>();
		Iterator itr = al.iterator();
		while (itr.hasNext()) {
			int ele = (int)itr.next();
			if (ele%2==1) res.add(ele);
		}
		return res;
	}
	
	// 6. Array to List, List to Array
	private static void arrayToListViceVersa(ArrayList<Integer> arl, int[] ar) {
		Integer arr[] = arl.toArray(new Integer[0]);
		System.out.println("Convert List to Array = " + Arrays.toString(arr));
		List<Integer> lst = Arrays.asList(arr);
		System.out.println("Convert Array to List = " +  lst);
	}
	
	private static ArrayList<Integer> insertValuesIntoAL() {
		Integer[] ar = {30,40,60,10,94,23,05,46, 40, 94};
		ArrayList<Integer> arl = new ArrayList<>();
		Collections.addAll(arl, ar);
		//Collections.reverse(al);   //IN BUILT METHOD
		return arl;
			//Arrays.sort(ar);  
		//List lst = Arrays.asList(ar);    //TBD
		//return new ArrayList<Integer>(lst);
		
	}

}