We are doing add two strings.

public class addition_of_two_string_value 
{
  public static void main(String[] args) 
  {
    String firstName = "John ";
    String lastName = "Doe";
    String fullName = firstName + lastName;
    System.out.println(fullName);  
  }
}

We are doing add two integer numbers and print result.

public class addition_of_two_int_value 
{
  public static void main(String[] args) 
  {
    int x = 5;
    int y = 6;
    System.out.println(x + y); // Print the value of x + y
  }
}

We are calling an interface method that does not have an body.

interface Animal 
{
  public void animalSound(); // interface method (does not have a body)
  public void sleep(); // interface method (does not have a body)
}

class Pig implements Animal 
{
  public void animalSound() 
  {
    System.out.println("The pig says: wee wee");
  }
  public void sleep() 
  {
    System.out.println("Zzz");
  }
}

class call_interface_method_which_does_not_have_a_body 
{
  public static void main(String[] args) 
  {
    Pig myPig = new Pig();
    myPig.animalSound();
    myPig.sleep();
  }
}

We are doing cast an integer data to double and print them.

public class Automatic_casting_int_to_double 
{
  public static void main(String[] args) 
  {
    int myInt = 9;
    double myDouble = myInt; // Automatic casting: int to double

    System.out.println(myInt);
    System.out.println(myDouble);
  }
}

We are doing modify value through call a method of class.

class A
{
	int x;
	void f1()
	{
		int y=5;
		 x=y;
	}
}
class call_f1_method_through_object_of_class_A_and_print_some_value_of_object2
{
   public static void main(String[] aa)
   {
	   A a=new A();
	   a.f1();
	   System.out.println(a.x);
   }
}

We are doing print sum of numbers though call a method.

public class before_call_and_print_myMethod_parameterised_function_using_return 
{
  static int myMethod(int x, int y) 
  {
    return x + y;
  }

  public static void main(String[] args) 
  {
    int z = myMethod(5, 3);
    System.out.println(z);
  }
}