Classes - Static and Instance

Math.random() is an example of a static method

• True

• False

What is true about this code running in a client program?

• This code will not compile no matter what

• This code will compile no matter what

• This code will only compile if printIdNum is an instance method

• This code will only compile if printIdNum is a static method

What is the difference between "static" and "instance"?

• Static items belong to the object, instance items belong to the class

• Static items belong to the class, instance items belong to the object

• Static refers to variables, instance refers to methods

• Static refers to methods, instance refers to variables

Which of the following is TRUE about instance variables

• They can be accessed from within a class without an accessor method

• They can be accessed from outside a class without an accessor method

• You must both declare and instantiate them before your constructor

• They must be public

Which is NOT true about default constructors

• Java will create a default Constructor if you forget to write one

• A default constructor cannot use negative numbers

• A default constructor cannot have parameters

• A default constructor cannot have a return type

What does the "new" keyword do?

• Create a new spot in memory for a class data type

• Create a new spot in memory for a primitive data type

• Declare a new variable

• Initialize a new variable

What does a constructor do?

• Create a new spot in memory for a class data type

• Declare instance variables

• Initialize the values of the instance variables

• Create a new class

Which of the following is FALSE about the toString() method?

• It is a special method that can be called automatically by printing an object

• It is called automatically when you print the this keyword from within a class

• It always returns a String type

• It always has String parameters

Which of the following is TRUE about instance variables and the parameters in a constructor

• You must use the same name for parameters and variables

• There will be an error if parameters and variables have the same name

• You should not use the same name for parameters and variables

• You should not use different names for parameters and variables

Which of the following is TRUE of static variables

• Static variables can only be accessed by static methods

• Static variables cannot be initialized in a constructor

• Static variables are shared among all instances of a class

• Static variables must be declared final