[9-2] equals ()&toString 오버라이딩

class Exercise9_2 {
public static void main(String[] args) {
Point3D p1 = new Point3D (1,2,3);
Point3D p2 = new Point3D (1,2,3);

System.out.println(p1);
System.out.println(p2);
System.out.println("p1==p2?"+(p1==p2) );
System.out.println("p1.equals (p2) ?"+(p1.equals(p2) ) );

}
}

class Point3D {
int x, y, z;

Point3D (int x, int y, int z) {
this.x = x;
this.y = y;
this.z = z;

}

Point3D () {
this (0,0,0);
}

public boolean equals (Object obj) {
if (obj instanceof Point3D) {
Point3D p = (Point3D)obj;
return x == p.x && y == p.y && z == p.z;
}
return false;
}

public String toString () {
return "["+x+","+y+","+z+"]";
}
}