java.lang.Object o = 1;//why does this compile?

Question

I was doing one of these online Java tests and I was asked this question:

Q: Indicate correct assignment:

Long l = 1; 
Double d = 1;
Integer i = 1;
String s = 1;
Object o = "1";
System.out.println(o);
o = 1;
System.out.println(o);

Please try it yourself before you go any further.

Well I can tell you I got it wrong, I investigated it and found:

//Long l = 1; //cannot widen and then box
Long ll = 1L;//no need to widen, just box
//Double d = 1;//cannot widen and then box
Double dd = 1d;//no need to widen, just box
Integer i = 1;//no need to widen, just box
//String s = 1;//cannot do implicit casting here

Object o = "1";//this compiles and is just plain weird 
System.out.println(o);//output is 1
o = 1;//this also compiles and is also weird 
System.out.println(o);//output is 1

Can someone tell why:

Object o = 1; and Object o = "1";

compile and output 1 in both cases, this is puzzling me.

Many thanks

Answer 1

"1" is an instance of String class, and String is a subclass of Object class in Java (as any other class). 1 is boxed into an Integer, which is also derived from Object.