SCJP Sun Certified Programmer By Kathy Sierra and Bert Bates - Part4

Couple of weeks back i started practicing SCJP Sun Certified Programmer for Java 5 Study Guide By Kathy Sierra and Bert Bates.

Great book written by Kathy Sierra and Bert Bates.

I wanted to share few important quotations found from the fourth chapter.

1) It is legal to test whether the null reference is an instance of a class. This will always result in false, of course. For example:

class InstanceTest {
   public static void main(String [] args) {
      String a = null;
      boolean b = null instanceof String;
      boolean c = a instanceof String;
      System, out.println (b + " " + c) ;
   }
}

prints this: false false

2) Below table summarizes the use of the instanceof operator given the following:

interface Face { }
class Bar implements Face{ }
class Foo extends Bar { }

First Operand (Reference Being Tested)	instanceof Operand (Type We're Comparing the Reference Against)	Result
null	Any class or interface type	false
Foo instance	Foo, Bar, Face, Object	true
Bar instance	Bar, Face, Object	true
Bar instance	Foo	false
Foo[]	Foo, Bar, Face	false
Foo[]	Object	true
Foo[]	Foo, Bar, Face, Object	true

3) The || and && operators work only with boolean operands.

4) Difference between short-circuit and non-short-circuit logical operators.

int z = 5;
if(++z > 5 | | ++z > 6) z++;   // z = 7 after this code

versus:

int z = 5 ;
if (++z > 5 | ++z > 6) z++;   // z = 8 after this code

5) There are six relational operators: >, >=, <, <= , ==, and !=. The last two ( == and ! = ) are sometimes referred to as equality operators.

6) instanceof is for reference variables only, and checks for whether the object is of a particular type.

7) The || does not evaluate the right operand if the left operand is true.

8) The & and | operators always evaluate both operands.