class Point {
    double x;
    double y;
    double z;
   
    public Point (double _x, double _y, double _z) {
        x = _x;
        y = _y;
        z = _z;
    }
   
    public void reworkX(double i) {
        x = i;
    }
   
    ……
}


public class kongjiandian {
    public static void main(String args[]) {
        Point s = new Point(3.2,2.4,3.5);
        Point y = new Point(0.0,0.0,0.0);
        System.out.println(s.distance(y));
    }
}

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class Point {
    double x;
    double y;
    double z;
   
    Point (double _x, double _y, double _z) {
        x = _x;
        y = _y;
        z = _z;
    }
   
    void reworkX(double i) {
        x = i;
    }
   
    ……
}


public class kongjiandian {
    public static void main(String args[]) {
        Point s = new Point(3.2,2.4,3.5);
        Point y = new Point(0.0,0.0,0.0);
        System.out.println(s.distance(y));
    }
}
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上面两种定义方法中第一种有public，而第二种没有public，我想问下两种方法有什么区别，是不是在那里都可以这样写？