Question

I want to create a method which takes a string argument and returns a class of that type.

For e.g. if I pass Long , it should return Long.class

psudo code:

private Class<?> classReturn(String className){
return new Class<className>;
}

Edit: : problem is I have values like "String" only. not "java.lang.String"

Edit2: I have a variable in String. I want to cast it to the above class.
For e.g.
String value=”1″;
String type= “Long”;
I want something like this (psudo code):

value = (classReturn(type)) value ;

Answer 1

You can use

Class.forName(className);

if you have using a short class name you need to implement a path like

The closest you can do to convert strings is to assume some convention such as valueOf or a constructor which takes a String.

public static <T> T parseAs(String text, String className) {
    Class clazz;
    FOUND:
    {
        ClassNotFoundException e = null;
        for (String pkg : "java.lang.,java.util.,java.math.,".split(",",-1)) {
            try {
                clazz = Class.forName(pkg + className);
                break FOUND;
            } catch (ClassNotFoundException e2) {
                e = e2;
            }
        }
        throw new IllegalArgumentException(e);
    }
    try {
        Method valueOf = clazz.getMethod("valueOf", String.class);
        return (T) valueOf.invoke(null, text);
    } catch (Exception e) {
        try {
            Constructor<T> valueOf = clazz.getConstructor(String.class);
            return (T) valueOf.newInstance(text);
        } catch (Exception e2) {
            throw new IllegalArgumentException(e);
        }
    }
}

enum BuySell {
    BUY, SELL
}
public static void main(String... args) {
    for (String className : "String,Long,Double,BigDecimal".split(",")) {
        Object o = parseAs("1", className);
        System.out.println(className + " => " + o.getClass() + " as " + o);
    }
    Object o = parseAs("BUY", BuySell.class.getName());
    System.out.println("BuySell => " + o.getClass() + " as " + o);
}

prints

String => class java.lang.String as 1
Long => class java.lang.Long as 1
Double => class java.lang.Double as 1.0
BigDecimal => class java.math.BigDecimal as 1
BuySell => class Main$BuySell as BUY