What will happen during the following code executi

What will happen during the following code execution?


import java.util.*;
public class Test {
    public static void main(String[] args) {
        List a = new ArrayList<Double>();// 4
        a.add("1.5");// 5
        List<Double> b = new ArrayList();// 6
        b.add("1.5");// 7
        System.out.println(a + " " + b);
    }
}

Compilation error in the 4th line
Compilation error in the 5th line
Compilation error in the 6th line
Compilation error in the 7th line
Runtime Error
[1.5] [1.5] will be displayed to the console

Explanation

Compilation error occurs in the seventh line, because only elements of Double type and derived from it can be added to the "b" collection. Elements of any type can be added to "a" collection, so parameterized type Double is stepped up to Object.