Re: How to cast an Object to Double?
www wrote:
....
The map definition(Map<String, Object> map = new HashMap<String,
Object>(10)) also show that the value is Object type.
There are two issues that are combined here, and are better kept separate:
1. The class of an object. The class of each object is specified when it
is created, either new or by cloning an existing object. It cannot be
changed during the object's life.
2. The type of a variable or expression. The type of a variable or
expression can be calculated at compile time.
A reference expression can point to some object if, and only if, the
type of the expression corresponds to the object's class, or to one of
its superclasses, or one of the interfaces it implements.
During an object's life, it may be referenced by expressions of any
appropriate type. Similarly, an expression may reference objects of
different classes at different times.
Object is the ultimate superclass, so an Object expression, such as the
result of get on a Map<String,Object> can reference ANY object,
regardless of its class. In this case, it happens to point to a String.
That String remains a String, regardless of whether the type of the
referencing expression is Object, String, Serializable, CharSequence, or
Comparable<String>.
Patricia