variables

variables

1. Primitives variables

   • Primitive Casting
   • Boxing, Autoboxing Unboxing, Auto-unboxing
     • Wrapper Classes
       • Boolean, Byte, Character, Short, Integer, Long, Float, Double
       • new Wrapper(primitif type) or new Wrapper(String) except new Character(char)
       • new Float(double) possible
       • static Wrapper.valueOf(String value[, int radix]):wrapper
       • static Wrapper.parseXxx(String value[, int radix]):primitive value
       • static Wrapper.toXxxString(int or long) (Binary, Hexadecimal, Octal):String
       • Wrapper Conversion Utilities wrapper.xxxValue():primitive value
       • ==, ++, -- involve auto-unboxing auto-boxing
       • != coparaison does not involve auto-unboxing auto-boxing
       • if(Boolean b) unbox
       • Exceptions
         • NumberFormatException
         • NullPointerException
   • boolean, byte, char, short, int, long, float, double
   • size matters

2. Reference variables

   • Reference Casting
   • type matters

3. Scope

   • Static variables: have the longest scope, they are created when the class is loaded, and they survive as long as the class stays loaded in the Java Virtual Machine (JVM)
   • Instance variables: created when a new instance is created, and they live until the instance is removed
   • Local variables: live as long as their method remains on the stack
   • liBlock variables: ve only as long as the code block is executing