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
– morgano, Commented Jul 26, 2013 at 9:36
What I understood you want something like this stackoverflow.com/questions/8918550/… — usman allam
– usman allam, Commented Jul 26, 2013 at 9:43
Do you mean 'convert'? You can't cast a Java String to anything except the interfaces it implements. — user207421
– user207421, Commented Jul 26, 2013 at 10:30

Igor G. · Accepted Answer · 2017-08-17 09:53:40Z

2

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, 2017 at 9:53

Igor G.

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rocketboy · Accepted Answer · 2013-07-26 10:14:58Z

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, 2013 at 10:14

rocketboy

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2 Comments

Igor G. Over a year ago

Kinda, var holds value, lets say "123" and type is Long. This code always throws ClassCastException.

rocketboy Over a year ago

"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?

Lajos Arpad · Accepted Answer · 2017-08-17 10:17:12Z

0

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) {

        }
    }

}

edited Aug 17, 2017 at 10:17

Lajos Arpad

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answered Jul 26, 2013 at 11:14

Prabhakaran Ramaswamy

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