1. March 29th Odds & Ends
CS 239

2. Re: instance variables
Public class DoSomething {
int count; // count is an instance variable
FACT 1: when a class is instantiated instance variables are initialized
FACT 2: variables of primitive types within a method MUST be initialized by the programmer

3. Look back at ChangeMaker trace
The detailed trace in the key only handles the j = 1 case in the initial call.
Still needs to handle the j=2 case in the initial call.

4. Overloading
When you overload a method the method names are the same but the parameter lists are different.

5. Strings
Are immutable
When you run the code on the next slide, you are not changing the value at the original storage location, you are being given a new storage location for the new String.
There is no way to get the address of a String or any other java Object.

6. String example public class TestString {
public static void main (String [] args)
String animal = “cat”;
System.out.println (animal);
animal = animal.concat(“bird”);
} // end main
} // end class

7. Addresses in Java Java doesn’t want you to see addresses
When we printed out numbers in class, what we were seeing was not an address. It was a hash code.

8. TestParameterPassing.java public class TestParameterPassing {
public static void main (String [] args)
{ Integer c,d; ParameterPassing myParameterPassing; myParameterPassing = new ParameterPassing(); // c = new Integer(7); // d = new Integer (13); c = 7; d = 13; System.out.println (" c = " + c + " d = " + d); // before call to swap myParameterPassing.swap(c,d); System.out.println (" c = " + c + " d = " + d); // after call to swap
} // end main
} // end class
In the current version of java, using c = 7; and d = 13; is equivalent to the commented out lines above. In either case, the swap method with two Integer parameters is the one that will be called.