Notes 30-06-2024

[nginx500]

Q1. 
package x.y.z;
public class Employee {
  static {
    System.out.println("sb1");
  }

  private static int id;
}

package a.b.c;
public class App {
  public static void main(String[] args){
    Employee.id = 20;
  }
}

// will this compile? 

Answer : No

Fix below:

package x.y.z;
public class Employee {
  static {
    System.out.println("sb1");
  }

  public static int id; // 2. make id as public so that it can be accessible inside App class
}

package a.b.c;
import x.y.z.Employee;  // 1. add import statement as App and Employee in different packages
public class App {
  public static void main(String[] args){
    Employee.id = 20;
  }
}

--------------------------------------------------------------------

Q2.

package x.y.z;
public class Employee {
  static {
    System.out.println("sb1");
  }

  public static int id;
}

package a.b.c;
import x.y.z.Employee;
public class App {
  public static void main(String[] args){
    Employee#id = 20;
  }
}

// Will this code compile? NO 

Answer: id is a static resource inside Employee class. it must be accessed 
using . operator instead of #

-----------------------------------------------------------
Q3.

package x.y.z;
public class Employee {
  static {
    System.out.println("sb1");
  }

  public static int id=4;

  static {
    m1(id);
    id=5;
  }

  public static void m1(int i){
    System.out.println(i*i);
  }
}

package a.b.c;
import x.y.z.Employee;
public class App {
  public static void main(String[] args){
    Employee.id = 20;
  }
}

// what is the output?

sb1 
16
--------------------------------------------------------------

Q4.

package x.y.z;
public class Employee {
  static {
    System.out.println("sb1");
  }

  public static int id=4;

  static {
    m1();
    id=5;
  }

  public static void m1(){
    System.out.println(id*id);
  }
}

package a.b.c;
import x.y.z.Employee;
public class App {
  public static void main(String[] args){
    Employee.m1(); // [sb1, 16], 25
    Employee.id=7;
    Employee.m1(); // 49
  }
}

// what is the output?

[nginx500]

1. Access static and instance resources of same class from instance area.
2. From static area can access only static resources, but not instance resources

[nginx500]

Static-Instance.pptx Datatype.pptx