static and more ch5_3

Question 1

what is meant by the term static variable?

Answer 1

• static objects are the objects that belong to the class - not to the instances of the class
• can only be used inside the class
  A static variableis a variable that belongs to the class as a whole, and not just to one object
  •There is only one copy of a static variable per class, unlike instance variables where each object has its own copy
• all objects of the class can read and change the static variable

Question 2

can a static method access an instance var?

Answer 2

no - static methods can only access static variables

Question 3

how to declare static variables

Answer 3

private static int mystaticvariable = 0 – initialized and declared at the same time

Question 4

static variables should always be declared private unless ….

Answer 4

is is also a defined constant

Question 5

static method

Answer 5

can be used without calling an object
A static method still belongs to a class, and its definition is given inside the class definition
- Static methods are invoked using the class name in place of a calling objectreturnedValue = MyClass.myMethod(arguments)

Question 6

pitfall: invoking a non static method within a static method

Answer 6

• A static method cannot refer to an instance variable of the class, and it cannot invoke a non-static method of the class
• A static method has no “this”, so it cannot use an instance variable or method that has an implicit or explicit this for a calling object
• A static method can invoke another static method,

Question 7

putting main in any class

Answer 7

• can be contained within a regular class definition
• In this way the class in which it is contained can be used to create objects in other classes, or it can be run as a program
• A main method so included in a regular class definition is especially useful when it contains diagnostic code for the class