When I execute this code it gives me the Exception Glthread 8 Java.lang.null.pointer
MouseJointDef md = new MouseJointDef();
md.bodyA = _body;
md.bodyB = _body;
md.target.set(locationWorld);
md.collideConnected = true;
md.maxForce = 1000.0f * _body.getMass();
_mouseJoint = (MouseJoint) _world.createJoint(md);
_body.setAwake(true);
Thanks.