Java

Static variable (also known as class variable)
Static method (also known as class method)

public class S
{
	private static int count = 0;

	public S()
	{
		System.out.println("Constructor ...");
		count++;
	}

	protected void finalize()
	{
		System.out.println("Finalize ...");
		count--;
	}

	public static void main(String args[])
	{
		S s1 = new S();
		S s2 = new S();

		System.out.println("Count: "+S.count);

		s1 = null;
		s2 = null;

		System.gc();

		System.out.println("Count: "+S.count);
	}
}

Static block is used for initializing the static variables

public class S
{
	private static String name;
	private static int year;
	static
	{
		name = "Lin";
		year = 37;
	}

	public static void main(String args[])
	{
		S s1 = new S();

		System.out.printf("Name: %s\nAge: %d\n", S.name, S.year);
	}
}

Nested static class doesn’t need reference of Outer class
A static class cannot access non-static members of the Outer class
Able to access instance attributes and methods through an object reference
As a member of the OuterClass, a nested class can be declared private, public, protected, or package private
have access to other members of the enclosing class, even if they are declared private

public class S
{
	//non-static attribute
	private int age;

	//non-static methods
	public int getAge() {return age;}
	public void setAge(int a) {age = a;}

	//static attribute
	private static int count = 0;

	//static method
	public static int getCount() {return count;}

	//static class
	public static class C
	{
		private int year;

		public C(int y) { year = y;}

		public int getYear() { return year;}

		//access static attribute and static method
		public String toString() { return "C: "+year+" "+count+" "+getCount();}

		//access outer class
		public void display()
		{
			S s = new S();
			s.setAge(20);
			System.out.println("C: "+s.getAge());
		}
	}
}

public class STest
{
	public static void main(String args[])
	{
		//create static class object
		S.C c = new S.C(2017);

		System.out.println(c);
		c.display();
	}
}

Enable you to refer to imported static members as if they were declared in the class that uses them

import static java.lang.Math.*;

public class S
{
	public static void main(String args[])
	{
		System.out.printf("%10.2f\n", PI);
		System.out.printf("%10.2f\n", sqrt(10.0));
	}
}