Get Long value from Long Array exception in Java

Question

I want to try to get Long value from Long Array. But I've got this exception:

Exception in thread "main" java.lang.ClassCastException: java.lang.Integer cannot be cast to java.lang.Long

Code like this :

import java.util.List;        
    public class Bar {        
        private List<Long> departments;      

        public List<Long> getDepartments() {
            return departments;
        }     

        public void setDepartments(List<Long> departments) {
            this.departments = departments;
        }           

    }


import java.util.List;    
import net.sf.json.JSONObject;    
public class Foo {    
    public static void main(String[] args) {    
        String str = "{\"departments\":[20,22]}";
        JSONObject jsonObject = JSONObject.fromObject(str);
        Bar bar = (Bar) jsonObject.toBean(jsonObject, Bar.class);
        List<Long> departments = bar.getDepartments();
        Long depId = departments.get(0);// Exception in thread "main" java.lang.ClassCastException: java.lang.Integer cannot be cast to java.lang.Long
System.out.println(depId);

    }    
}

Probably because jsonObject.toBean injects at runtime a List of Integer instead of Long — Nicolas Filotto
– Nicolas Filotto, Commented Apr 7, 2016 at 11:37
Try JSONArray jsonArray = jsonObject.getJSONArray("department"); Collection<Long> depts = JSONArray.toCollection(jsonArray, List.class); if it helps. Haven't tried myself. Here is the JavaDoc of the toCollection() method: Returns a List or a Set taking generics into account. — ujulu
– ujulu, Commented Apr 7, 2016 at 14:21

muzahidbechara · Accepted Answer · 2016-04-07 12:56:32Z

1

public static void main(String[] args) {

    String str = "{\"departments\":[20,22]}";
    JSONObject jsonObject = JSONObject.fromObject(str);
    Bar bar =  (Bar) JSONObject.toBean(jsonObject, Bar.class);
    List departments = bar.getDepartments();
    Long i=  Long.valueOf(departments.get(0).toString());
    System.out.println(i);
    System.out.println(departments.get(0).getClass().getName());

}

It's a net.sf json cast bug, just cast to string

edited Apr 7, 2016 at 12:56

muzahidbechara

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answered Apr 7, 2016 at 11:55

JesseLin

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4 Comments

JesseLin Over a year ago

You can use jackson to void json cast exception

muammertuzun Over a year ago

Can not cast to string. Trying to String s = departments.get(0).toString(); throws same exception.

JesseLin Over a year ago

```public static void main(String[] args) { String str = "{\"departments\":[20l,22l]}"; JSONObject jsonObject = JSONObject.fromObject(str); Bar bar = (Bar) JSONObject.toBean(jsonObject, Bar.class); List departments = bar.getDepartments(); Long i= Long.valueOf(departments.get(0).toString()); System.out.println(i); System.out.println(departments.get(0).getClass().getName()); }

JesseLin Over a year ago

any class could to string

Shree Krishna · Accepted Answer · 2016-04-07 11:36:09Z

0

The you can try like this,

Long depId = (Long) departments.get(0).intValue();

Where intValue returns int, but then you cast it to Long.

answered Apr 7, 2016 at 11:36

Shree Krishna

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1 Comment

Shree Krishna Over a year ago

@MuammerTÜZÜN Can you show what departments.get(0) returns actually without storing it to any variables. Just by logging or printing it

muzahidbechara · Accepted Answer · 2016-04-07 12:02:24Z

0

Try this

Long depId = departments.get(0).longValue();

EDIT:

Integer i = 9;
Long l = i.longValue();
System.out.println(i + "  " + l);

edited Apr 7, 2016 at 12:02

answered Apr 7, 2016 at 11:36

muzahidbechara

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4 Comments

muammertuzun Over a year ago

did not work. Exception in thread "main" java.lang.ClassCastException: java.lang.Integer cannot be cast to java.lang.Long at com.test.Foo.main(Foo.java:16)

muammertuzun Over a year ago

departments.get(0) method's return type is Long but its try to return Integer. This is the source of the problem.

muzahidbechara Over a year ago

if departments.get(0) return still a Integer it will be converted to Long by longValue() method. Plz check again and inform me.

tak3shi Over a year ago

@Md. muzahidul Islam Do not think in Java, this is a problem at bytecode level due to a bug in the toBean method.

Ameya Patkar · Accepted Answer · 2016-04-07 12:16:06Z

0

Long i= Long.valueOf(departments.get(0).toString()); will solve your problem

answered Apr 7, 2016 at 12:16

Ameya Patkar

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1 Comment

muammertuzun Over a year ago

Your code is working when; List departments = ... ; but i defined like this List<Long> departments = .. ; same error continues.

tak3shi · Accepted Answer · 2016-04-07 12:40:01Z

0

The toBean() method produces a different Class with List<Integer>. I do not see any reason to cast an Integer to Long due to this bug. Change departments to List<Integer> or use an another JSon Parser.

answered Apr 7, 2016 at 12:40

tak3shi

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Comments

Abacus · Accepted Answer · 2016-04-10 08:59:33Z

0

JSON itself has not notion of Integer or Long, it just know Number. A Number value - or a list of that - is put into an Integer object by JSONObject if it is not a floating pint value.

The fact that you declared the List as a List<Long>is not relevant for JSONObject, as this generic type information is not available in the compiled class code (type erasure), there departments is just a list of objects and so JSONObject happily fills in Integer objects.

You could either declare departmentsas List<Integer> or use additional transformation methods (have a look at ujulu's comment to your post)

answered Apr 10, 2016 at 8:59

Abacus

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