Points To Remember for SCJP www.techfaq360.com The datatype in a switch statement must be convertible to int, i.e., only byte, short, char and int can be used in a switch statement, and the range of the datatype used must cover all of the cases (case statements). An integer literal (w/o a decimal pt) is assumed to be a 32-bit int primitive, but a value containing a decimal point is assumed to be a 64-bit double. Wrapper classes for primitives produce immutable objects. •Java characters are 16-bit unicode characters, and they can be initialized in the following ways: char c1 = '\u0057' char c1 = 'w' char c1 = 87 char c1 = (char) 87 (acc to RHE) char c1 = '\r' •instanceof operator can take a class, an interface or an array type as an …ver más…

op1 instanceof op2 op1 must be the name of an object and op2 must be the name of a class. An object is considered to be an instance of a class if that object directly or indirectly descends from that class. There is nothing like instanceOf in java x instanceof P If x is null, the instanceof test simply returns FALSE --it doesn't cause an exception String[] str = new String[10]; now str instanceof String[] ===returns true str instanceof Object ===returns true str instanceof Object[] ===returns true str instanceof String ===Compilation Error •If a = null, System.out.println (a); prints null, and does not throw an exception. •A class SHOULD (MUST) be declared abstract if it has one or more abstract methods. An abstract class can also have non-abstract methods. You can also declare a class to be abstract even when it has no abstract methods, so that users can't instantiate it and are forced to subclass

it. •In an interface, ALL methods must be abstract. Infact, all methods in an interface are implicitly abstract. Also, all methods and variables in an interface are implicitly public, and must declare them to be public while implementing the interface. •It is a compile-time error for a constructor to invoke itself by calling this(), but there is a bug which allows cyclic constructor invocation, that is constructor 1 calls constructor 2 and vice-versa. •If you call Thread.sleep() in a synchronized code,