A question that I came across:
Q: Can you pass a double to a method when it's argument is a float?
A: No. Regardless of the double value, a double-sized variable is too big to fit in a float, so it can't be implicitly cast.
Doubt: Shouldn't narrowing happen implicitly?
Shouldn't narrowing happen implicitly?
There could be data lost. The programmer should tell the compiler that he knows what he is doing.
Java Language Spec says:
5.3 Method Invocation Conversion
Method invocation conversion is applied to each argument value in a method
or constructor invocation (§8.8.7.1, §15.9, §15.12): the type of the argument
expression must be converted to the type of the corresponding parameter.
Method invocation contexts allow the use of one of the following:
• an identity conversion (§5.1.1)
• a widening primitive conversion (§5.1.2)
• a widening reference conversion (§5.1.5)
• a boxing conversion (§5.1.7) optionally followed by widening reference
conversion
• an unboxing conversion
...
If the type of the expression cannot be converted to the type of the parameter by
a conversion permitted in a method invocation context, then a compile-time error
occurs.
so a narrowing conversion like double to float is not allowed.
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