how to cast string to integer at runtime

Question

I am using reflection in java.

I am getting to know the type of method parameter I am passing at run time. So I am fetching the parameter value from file into a string variable.

SO now if i get to know that the parameter type as integer and if i pass an object containting the string value I am getting

argument type mismatch java.lang.IllegalArgumentException: argument type mismatch

Class classDefinition = Class.forName("webservices."+objectName);

String methodName = set"+fieldNameAttay[i].substring(0,1)).toUpperCase()+fieldNameAttay[i].substring(1); Field f = classDefinition.getDeclaredField(fieldNameAttay[i]);

       try 
    {        
        //argType = f.getType();
              Method meth = classDefinition.getMethod(methodName,f.getType()); 

              Object arg = new Object[]{fieldValueArray[i]}; //fieldValueArray[i] is always string array 
                   meth.invoke(object, arg);   //If f.getType is Integer this //throws ex
                                   }
          catch (Exception e) 
          {
             System.err.println(e.getMessage());
             e.printStackTrace();
          }

Jon Skeet · Accepted Answer · 2010-12-27 10:05:12Z

5

You can't cast a string to an integer - you can parse it though. For example:

if (parameterType == int.class && argumentType == String.class)
{
    int integerArgument = Integer.parseInt((String) argumentValue);
    // Now call the method appropriately
}

Of course, you also need to consider Integer as well as int.

answered Dec 27, 2010 at 10:05

Jon Skeet

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Comments

Bozho · Accepted Answer · 2010-12-27 10:05:10Z

1

How about

Integer.parseInt((String) stringObj)

Note that casting can happen only if the two objects belong in the same hierarchy. So this is not casting.

answered Dec 27, 2010 at 10:05

Bozho

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Comments

fish · Accepted Answer · 2010-12-27 12:37:45Z

If the only types you are using are String and Integer, checking the type and then using Integer.parseInt might be the simplest thing to do.

However if you have more different types, I would suggest checking out the good old JavaBeans framwork: http://download.oracle.com/javase/tutorial/javabeans/index.html

And especially the PropertyEditors http://download.oracle.com/javase/7/docs/api/java/beans/PropertyEditor.html http://download.oracle.com/javase/7/docs/api/java/beans/PropertyEditorManager.html

The PropertyEditors allow you to set the value as text, and then retrieve the value as correct type. Assuming you have implemented and registered the property editors, the steps to get the correct type are similer to this:

Find out the type of the parameter
Retrieve a PropertyEditor for that type
Use setAsText and getValue in the property editor to convert the value to correct type

...or You can just adapt the same mechanism to your simple needs by implementing your own conversion framework with similar but simpler interfaces.

user467871 · Accepted Answer · 2010-12-27 10:10:25Z

0

System.out.println(Integer.parseInt(obj.toString()))

answered Dec 27, 2010 at 10:10

user467871

Comments

Gondim · Accepted Answer · 2010-12-27 14:21:51Z

0

There's another way to do it:

Integer number = Integer.valueOf("1");

answered Dec 27, 2010 at 14:21

Gondim

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