Java - get an Integer value from String or int - avoiding instanceof

Question

Is there a single line implementation for the getInt method?

If not - can one implement it without using instanceof?

public class ParseInt {
    public static void main(String[] args) {
        Object intArr[] = { "131", 232, new Integer(333) };

        for (Object intObj : intArr) {
            System.out.println(getInt(intObj));
        }
    }

    private static int getInt(Object obj) {
        return // ???
    }
}

Why do you even mention reflection? There's no need for it. There *is* need for `instanceof`, though, but that's not reflection. — Marko Topolnik, Nov 03 '14 at 12:07
`return obj instanceof Number? ((Number)obj).intValue() : Integer.parseInt((String)obj);` — Marko Topolnik, Nov 03 '14 at 12:09
possible duplicate of [How to cast an Object to an int in java?](http://stackoverflow.com/questions/3661413/how-to-cast-an-object-to-an-int-in-java) — Santhosh, Nov 03 '14 at 12:10

score 1 · Accepted Answer · answered Nov 03 '14 at 12:14

1

Use Integer.valueOf(obj.toString)

private static int getInt(Object obj) {
    return Integer.valueOf(obj.toString());
}

This will work for your object array

answered Nov 03 '14 at 12:14

This would die in the event that `obj` was `null`. You could use `String#valueOf(Object)` instead, which returns the String `"null"` if the passed argument is `null`. – JonK Nov 03 '14 at 12:16
@JonK - `String#valueOf(Object)` will throw `NumberFormatException` instead of `NPE`. Why is your suggestion better? – Elist Nov 03 '14 at 15:31
@Elist Really it's a matter of personal preference. It's for you to decide which exception is more meaningful for a given situation. If you would prefer a `NullPointerException` then go for that instead. – JonK Nov 03 '14 at 16:52

Vicky Thakor · Answer 2 · 2014-11-03T12:14:35.923

0

Try something like...

private static int getInt(Object obj) {
    if (obj instanceof String) {
        return Integer.parseInt((String) obj);
    } else if(obj instanceof Integer){
        return (Integer) obj;
    } else{
        return 0; // or else whatever you want
    }
}

edited Nov 03 '14 at 12:14

answered Nov 03 '14 at 12:09

Vicky Thakor

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You could also use `String#valueOf(Object)` instead of a cast – JonK Nov 03 '14 at 12:11
1

Let's just hope `obj` is not an instance of `XXX` (any class but `String` or `Integer`) – Nov 03 '14 at 12:12

Java - get an Integer value from String or int - avoiding instanceof

2 Answers2