Alternative path not working

I am using Android studio (libGDX), and I can’t figure out why alternative paths doesn’t work. I’ve tried it as it said in the book, but it doesn’t do anything, it shows a black window and than the program exterminates.
If the .png file would be in the …/android/assets/ folder, it wouldn’t work either.

Book: Java Game Development with LibGDX 2nd edition

This is what the book wants me to do it:

public Spaceship(float x, float y, Stage s){

    super(x,y,s);
    loadTexture( "assets/spaceship.png" ); 
    setBoundaryPolygon(8);

    setAcceleration(200);
    setMaxSpeed(100);
    setDeceleration(10);
}

This is the shortest form that works for me:

public Spaceship(float x, float y, Stage stage) {

    super(x, y, stage);

    loadTexture("core/src/com/dusi/game/ch04/assets/spaceship.png");
    setBoundaryPolygon(8);

    setAcceleration(400);
    setMaxSpeed(200);
    setDeceleration(20);
}

This is what my path looks like: