I can't run the code that I make on eclipse on other IDEs or VSCode

i’m studying java(i’m a beginner) in college and we use eclipse. i would like to try other ides but i can’t run code on any other than eclipse.
we do not use a main class, i know that may sound weird, but it works in eclipse (i guess).
we do exercises with arrays matrixes images, colours that kinda stuff. here’s an example:

static boolean[][] chessMatrix(int lines) {
    boolean[][] m = new boolean[lines][lines];
    for (int i = 0; i < m.length; i++) {
        for (int j = 0; j < m.length; j++) {
            if ((i + j) % 2 == 0) {
                m[i][j] = true;
          } else
                m[i][j] = false;
       }
    }
return m;
}

this code runs perfectly fine on eclipse, we use a debugger made by some college professors
on intelij, for example, it does not even give me the option to run. i have tried importing the src file directly, changed jre/sdk versions and i can’t get it to work. any help is appreciated, thanks!

>Solution :

Method needs to be part of a class, easiest is to create a class with a main method and put your method inside that class.

Example:

public class Main {

    public static void main(String[] args) {
        chessMatrix(10);

    }

    static boolean[][] chessMatrix(int lines) {
        boolean[][] m = new boolean[lines][lines];
        for (int i = 0; i < m.length; i++) {
            for (int j = 0; j < m.length; j++) {
                if ((i + j) % 2 == 0) {
                    m[i][j] = true;
                } else
                    m[i][j] = false;
            }
        }
        return m;
    }
}

Given the source above being saved as file "Main.java", you can compile first, then run that using:

javac -d . Main.java
java Main

Never versions of Java (AFAIK 11 and above) can also compile and run source code directly, using

java Main.java

Notes:

• the method above just created and returns a sqare array of boolean, so expect no visible output
• things get complicated when you use multiple source files, packages and external libraries. That’s the time you should consider using build management tools like Apache Maven or Gradle.