java 1.6 arraylist object cannot cast to string

Question

I have a problem trying to read the contents in my peakperiod list. The error I have received is java.lang.object cannot be cast to java.lang.String.
Are there any possible workaround for this problem as I am using java 1.6?

Delegate.java

 List peakPeriod = new ArrayList();  
 try{
     peakPeriod = Dao.retrievePeakPeriod("2017");
 for (Iterator i=peakPeriod.iterator(); i.hasNext(); {
     System.out.println("Peak Periods:"+(String)i.next());
 }
 catch(Exception e){ System.out.println("Error:"+e);}

Dao.java

public List retrievePeakPeriod(String year) throws DataAccessException;

DaoImpl.java

public List retrievePeakPeriod(String year) throws DataAccessException {
    List list = getHibernateTemplate().find("select cal.startdate,cal.enddate from Calendar cal " +
            "where to_char(cal.startdate,'yyyy') = ?",
            new Object[] { year },
            new Type[] { Hibernate.STRING });

    return list;
}

Don't use raw types. stackoverflow.com/questions/2770321/…. Your query returns a List<Object[]>. So it's quite expected that casting its element to String would fail. — JB Nizet
– JB Nizet, Commented Feb 19, 2017 at 9:06
Thanks and understood. However, I couldn't use <> for java 1.6 but had to use arraylist to retrieve the results. — Nosnos
– Nosnos, Commented Feb 19, 2017 at 9:19
Generics were introduced in Java 5, in 2004, so 13 years ago. 2 years before the first version of Java 6 came out. So yes, you definitely can use generics in Java 6. — JB Nizet
– JB Nizet, Commented Feb 19, 2017 at 9:21

LazyCubicleMonkey · Accepted Answer · 2017-02-19 09:28:15Z

1

System.out.println("Peak Periods:"+ i.next());

You don't have to cast it to a String - java will automatically call the toString() method, so the above is equivalent to:

System.out.println("Peak Periods:"+ i.next().toString());

If your list can have nulls, you can do something safer such as:

System.out.println("Peak Periods:"+ String.valueOf(i.next()));

Edit: This assumes that the object returned has a useful toString representation and it's what you want. Otherwise, you'd need to figure out the type (class) of (the) object that's returned and do with it what you want.

edited Feb 19, 2017 at 9:28

answered Feb 19, 2017 at 9:08

LazyCubicleMonkey

1,24310 silver badges17 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

Nosnos Over a year ago

Thanks for the swift reply. I have tried the 3 above solution but the result are similar. Peak Periods:[Ljava.lang.Object;@40dc76dd Peak Periods:[Ljava.lang.Object;@49ffc86f Peak Periods:[Ljava.lang.Object;@37c0155d Peak Periods:[Ljava.lang.Object;@23baa943 Peak Periods:[Ljava.lang.Object;@33be8008

JB Nizet Over a year ago

@JanosFang Which shows what I'm telling you in my comment: your query returns a List<Object[]>, not a List<String>. How could two fields (cal.startdate and cal.enddate) be stored in a single String?

Nosnos Over a year ago

@JBNizet Thanks JBNizet for identifying the cause. It was my blunder that did not took the parameters into consideration.

Collectives™ on Stack Overflow

java 1.6 arraylist object cannot cast to string

1 Answer 1

3 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

3 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related