Generic_Queue_using_Array_List.java

//Example
import java.util.Scanner;
import java.util.ArrayList;

class Queue<T> {
 private ArrayList<T> mArr;
 
 public Queue() {
 mArr = new ArrayList<>();
 }
 
 public void push(T val) {
 mArr.add(val);
 }
 
 public T pop() {
 if (mArr.size() < 1) return null;
 return mArr.remove(0);
 }
 
 public String toString() {
 String res = "";
 for (int i = 0; i < mArr.size(); ++i) {
 res += mArr.get(i).toString() + (i+1 == mArr.size() ? "" : " ");
 }
 return res;
 }
}

public class Main {
 private static <T> void print(Queue<T> q) {
 System.out.println("Queue insert done");
 System.out.println("Queue is: " + q);
 System.out.println("Queue is deleted: " + q.pop());
 System.out.println("Queue is deleted: " + q.pop());
 System.out.println("Queue is: " + q);
 }
 
 public static void main(String[] args) {
 Scanner sc = new Scanner(System.in);
 Queue<Integer> qi = new Queue<>();
 for (int i = 0; i < 6; ++i) qi.push(sc.nextInt());
 System.out.println("Queue Contents: " + qi);
 qi.push(sc.nextInt());
 print(qi);
 
 sc.nextLine();
 Queue<String> qs = new Queue<>();
 for (int i = 0; i < 6; ++i) qs.push(sc.next());
 System.out.println("Queue is: " + qs);
 qs.push(sc.next());
 print(qs);
 
 Queue<Double> qd = new Queue<>();
 for (int i = 0; i < 6; ++i) qd.push(sc.nextDouble());
 System.out.println("Queue is: " + qd);
 qd.push(sc.nextDouble());
 print(qd);
 }
}