Why doesn't output and show in red in Java?

Question

Java

Just started learning Java

package com.company;

public class Main {

    public static void main(String[] args) {

        class Square {
            Square(int i) {
                int x =i ;
}
        }

        class TestSquare {
            Square S1 = new Square(10);
            System.out.println(S1.x);
        }
    }
}

Answer 1

One main advice can be given to the author:
Take the resource you are currently working on, put it out of your head and never remember it again. The code is cosmically bad, and not because you are a beginner, but because you are taught not to understand what.
Classes in Java serve a purpose, for what purpose your classes are created is completely incomprehensible, except that, as mentioned above, creating classes in main is nonsense

// Class declaration
public class Test {

    // number exponentiation
    public int squareNumber(int i) {
        return i *= i;
    }

    // factorial
    public int factorial(int i) {
        return (i <= 1) ? 1 : (i * factorial(i - 1));
    }

    // main method
    public static void main(String[] args) {
        Test test = new Test(); // new instance
        System.out.println(test.squareNumber(5)); // 25
        System.out.println(test.factorial(5)); // 120
    }
}

Also check out what camelCase is, how it is accepted in java, and so on. This is a simple but extremely important question to understand.

Answer 2

Firstly, at first it is better to read the very basics than to already climb with stupid questions.
Secondly, edit your code by adding the tag
PS
1. Move the variable x from the constructor to the class level
2. There is no println8 method
3. In general, creating classes in the main method is a complete game

Answer 3

Because in the presumably function

Square(int i)

you're assigning x = i instead of squaring i and storing the result in x.

Answer 4

Good question, not stupid at all. The question is obviously being asked by a newbie, and he's already been splattered with toxins.
It makes no sense to explain the error, it makes sense to advise you to review the videos on the basics of java.
To do this: Square.xyou need to learn what class fields are.