Archive for Static

what’s static?

Posted in Programming with tags , , on April 14, 2008 by wsjoung

First of all, the meaning of static in java is embedded or belong to a specific class not to its instance, and therefore there is no such static class.

  • There is no such static class
  • Embedded or belong to a specific class
  • Global variable
  • No need to load and create its instance

Most of methods and variables in Math class are static, because those are not need to be instanced in most of cases. we just use return value of PI or max(int a, int b).

class Bicycle {

private static int numberOfBicycles = 0;
private int id;

public Bicycle() {
id = ++numberOfBicycles;
}

public static int getNumberOfBicycles() {
return numberOfBicycles;
}
public int getID() {
return id;
}

public static void main(String[] args) {
Bicycle b1 = new Bicycle();
Bicycle b2 = new Bicycle();

System.out.println(“static result : “+getNumberOfBicycles());
System.out.println(“static result : “+numberOfBicycles);
System.out.println(“instance result : “+b1.getID());
System.out.println(“instance result : “+b2.getID());
}
}

Another characteristic of static is that even if we create instance of a class, jvm does not create instance variables for static resources. in above source code, there is no difference calling b1.getNumberOfBicycles(), b2.getNumberOfBicycles() and just getNumberOfBicycles() or directly numberOfBicycles
that mean we should call static variable with its class name because it’s belong to it. just like Bicycle.numberOfBicycles or in this example, getNumberOfBicycles() because we have a getter.
otherwise get confused.

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