static

• In interface, static can be used to define utility functionality that is common for all classes implementing the interface.
• It is not recommended to call static fields/methods using object reference, Always use class reference to refer static fields/methods
• Example: System.out.println() is static method

Fields

• static fields in class are known as Class Fields
• They can be accessed by Class Name directly: ClassName.fieldName
• Generally, declaring non-final public static fields is not a good practice

Constants

• static final fields are also known as Class Constants
• the naming convention is to use uppercase with underscores
• They can only be initialized using static initialization block if they are not initialized when declared
• See static initializer

class A {    
    private static final int x;
 
    static {
        x = 5;
    }
}

Methods

• aka Class Methods
• They have following features:
  • They can access only static fields and cannot access non-static fields
  • They can invoke another static method, but it cannot invoke an instance method
  • They cannot refer to this keyword because there is no instance in the static context
  • They cannot refer to super keyword
• Instance methods, however, can access static fields and methods.
• Only way to call instance methods from static method is to pass instance as an argument to static method
• Examples:
  • Math.abs(val), Math.pow(x, y)
  • Long.valueOf(...), Integer.parseInt(...), String.valueOf(...)

static class

• See Static Nested Class

static initializer block

• See static initializer