java - Why can't I access a protected method? -

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• why code wrong , java in nutshell said so? [closed] 1 answer

i have question protection mechanism different packages in java. can not understand is, why method call not work!

package a; class  {     protected void method(){};  }  package b; import a.a;  class b extends {  }  class main extends {     b b = new b();     b.method();// error: method() has protected access in package1.a }  why!! 

jls 6.6.2

a protected member or constructor of object may accessed outside package in declared code responsible for implementation of object.

being subclass doesn't mean responsible of implementation.

here example, again jls :

package points; public class point {     protected int x, y;     void warp(threepoint.point3d a) {         if (a.z > 0)  // compile-time error: cannot access a.z             a.delta(this);     } } 

package threepoint; import points.point; public class point3d extends point {     protected int z;     public void delta(point p) {         p.x += this.x;  // compile-time error: cannot access p.x         p.y += this.y;  // compile-time error: cannot access p.y     }     public void delta3d(point3d q) {         q.x += this.x;         q.y += this.y;         q.z += this.z;     } } 

a compile-time error occurs in method delta here: cannot access protected members x , y of parameter p, because while point3d (the class in references fields x , y occur) subclass of point (the class in x , y declared), not involved in implementation of point (the type of parameter p). method delta3d can access protected members of parameter q, because class point3d subclass of point , involved in implementation of point3d.