How to convert a string value to some concrete type?

Question

I have a string value and a class object of a concrete type.

So my question is how to convert a string value to that type?
It really looks like the only possible way is to do something like this:

private Object convertTo(String value, Class type) {
    if(type == long.class || type == Long.class)
        return Long.valueOf(value);
    if(type == int.class || type == Integer.class)
        return Integer.valueOf(value);
    if(type == boolean.class || type == Boolean.class)
        return Boolean.valueOf(value);
    ...
    return value;
}

But that looks ugly ... is there any nicer way to do that?

Show us the code, it is better understandable with lines of code — morgano, Jul 26 '13 at 09:36
What I understood you want something like this http://stackoverflow.com/questions/8918550/cast-via-reflection-and-use-of-class-cast — usman allam, Jul 26 '13 at 09:43
Do you mean 'convert'? You can't *cast* a Java String to anything except the interfaces it implements. — user207421, Jul 26 '13 at 10:30

score 1 · Accepted Answer · answered Aug 17 '17 at 09:53

1

What I was really looking for is some sort of generic type conversion. The one that worked the most for me is from Spring:

 org.springframework.core.convert.support.DefaultConversionService

answered Aug 17 '17 at 09:53

Igor G.

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score 0 · Answer 2 · answered Jul 26 '13 at 10:14

0

According to what you describe, if you have:

String var = "variable";
Class<?> type = Class.forName("your_class");// Your type
Object o = type.cast(var);

Now 3 things can happen:

o should be of your_class type
If var is null, o will be null or
ClassCastException will be thrown

answered Jul 26 '13 at 10:14

rocketboy

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Kinda, _var_ holds value, lets say "123" and type is Long. This code always throws ClassCastException. – Igor G. Jul 26 '13 at 10:22
"123" cannot be casted to Long or Integer for that matter. That is why we have functions like atoi and itoa. Is your expectation valid? – rocketboy Jul 26 '13 at 11:42

score 0 · Answer 3 · edited Aug 17 '17 at 10:17

public class Sample {

    /**
     * @param args
     */
    public static void main(String[] args) {

        List<Class<?>> classList= new ArrayList<Class<?>>();
        classList.add(String.class);
        classList.add(Double.class);
        try {
            Class<?> myClass = Class.forName("java.lang.Double");
            //Object newInstance = myClass.newInstance();           

            for (Object object : classList) {               
                if(myClass.equals(object)){
                    //do what you like here
                    System.out.println(myClass);
                }

            }

        } catch (ClassNotFoundException e) {

        }
    }

}

How to convert a string value to some concrete type?

3 Answers3