Static Methods
- Static methods are declared using a static modifier.
- Static methods can not access instance methods and instance variables directly.
- Static methods usually used for operations that do not require any data from an instance of the class (from
this). - This keyword is the current instance of a class.
- A method that does not use instance variables that method should be declared as a static method.
main is a static method and it is called by the JVM when it starts an application.
Static Method
package anote;
public class Main {
public static void main(String[] args) {
int result = Calculator.sum(3, 2);
System.out.println(result);
hello("world");
}
public static void hello(String word) {
System.out.println("hello " + word);
}
}
class Calculator {
public static int sum(int a, int b) {
return a + b;
}
}Static method do not require to create instance. Just called class name dot method name to access them.
Instance Methods
- Instance methods belong to an instance of a class.
- To use an instance method we have to instantiate the class first usually by using the new keyword.
- Instance methods can access instance methods and instance variables directly.
- Instance methods can access static methods and static variables directly.
package anote;
public class Main {
public static void main(String[] args) {
Car car = new Car();
car.engineSound();
}
}
class Car {
//instance methods do not use static keywords
public void engineSound() {
System.out.println("www");
}
}Static or instance method?
Does it use any fields (instance variables) or instance methods?
- if yes, instance method
- if no, static method