I have some mistakes

Question

What is the output of this code?
class A {
int x;
public A(int y) {
x=y;
}
public String toString() {
return "x";
}
}
public class B {
public static void main(String[] args) {
System.out.print(new A(10));
}
}

why the output is x
where is the call of toString?

Answer 1

A bit more about toString();

A test = new A(10);

Implicit calling of toString():

System.out.println(test);

--> if you don't override the toString() method you get something like this:
className + [a hashcode]
A[@4828]
--> not useful

You want 10 as output or maybe [10] or what ever you want.
That's why you write your own toString() method (which overrides the default toString())

Explicit calling:
System.out.println(test.toString());

But you don't need to do this.

Answer 2

so the method toString exists at Object class that all classes are inherited from it that why I have to override this method

Answer 3

thanks master Denise Roßberg

Answer 4

but where is the invocation of toString method

Answer 5

Output is an x, because the toString() returns "x".
It would be the same as String str = "x"; return str;

You can do this:
return "" + x;
or this:
return Integer.toString(x);

Answer 6

You can also read this:
https://www.baeldung.com/java-tostring

Answer 7

The method is part of java.lang.Object.
https://docs.oracle.com/javase/7/docs/api/java/lang/Object.html

Edit: Try to print an array (without using Arrays.toString()) then you see it why it is better to override it.

Answer 8

Your welcome :)

Answer 9

The invocation of the toString is implicit. When you write System.out.print (test);
the compiler reads it as System.out.print (test.toString());

Also as said above your toString will always return x as a string as opposed to x as a variable

Answer 10

or

public String toString() {
return String.valueOf(x);
}