CODEWITHSUNDEEP
java
Brandon
Brandon

Reputation: 23510

Class cast exception from Double to double

Why class cast exception from Double to double?

Used like:

Console.writeLine(Validator.TryParse("1.5", double.class));

Code:

public static <T> T TryParse(Object ConvertFrom, java.lang.Class<T> ConvertTo) {
        switch(ConvertTo.getSimpleName().toLowerCase()) {
            case "int":
            case "integer": return ConvertTo.cast((int)Integer.parseInt((String)ConvertFrom));      
            case "string": return ConvertTo.cast(String.valueOf(ConvertFrom));             
            case "double": return ConvertTo.cast((double)Double.parseDouble((String)ConvertFrom));              
            case "float": return ConvertTo.cast((float)Float.parseFloat((String)ConvertFrom));              
            case "long": return ConvertTo.cast((long)Long.parseLong((String)ConvertFrom));          
            default: return null;
        }
    }

Upvotes: 1

Views: 510

Answers (4)

Pablo Tricanico
Pablo Tricanico

Reputation: 31

If you still need to define the class each time you call the validator, why don't you just use the valueOf method of each class? The Object classes such as Integer and Double will be able to handle the primitives and return objects...

As it's been asked before, are you sure you need to implement this? You might want to review your design.

Upvotes: 1

jahroy
jahroy

Reputation: 22692

You can use Double.doubleValue() and Integer.intValue().

More reading:

Except....

Your method wants to return an Object, so you can't return primitives.

Editorial:

It seems like you're trying to do something that is very unnatural and un-Java (Java is a typed language for a reason).

Upvotes: 0

assylias
assylias

Reputation: 328669

You are mixing primitives and boxed primitives. Calling TryParse("1.5", Double.class) will work fine (and you can remove all the unnecessary primitive casts like (int) (double) etc).

The problem you encounter is that Class#cast first checks Class#isInstance and:

Double.class.isInstance(1.0);

is true but:

double.class.isInstance(Double.valueOf(1.0))
double.class.isInstance(1.0d)

are false as explained in the javadoc

If this Class object represents a primitive type, this method returns false.

Bottom line: primitive.class.cast() will always throw an exception.

Upvotes: 1

Jayamohan
Jayamohan

Reputation: 12924

It should be as below, Note the Caps in Double.

Console.writeLine(Validator.TryParse("1.5", Double.class));

Upvotes: 0

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