java.math.BigInteger 无法转换为 java.lang.Long

Question

I've got List<Long> dynamics . And I want to get max result using Collections . This is my code:

List<Long> dynamics=spyPathService.getDynamics();
        Long max=((Long)Collections.max(dynamics)).longValue(); 

This is my getDynamics :

public List<Long> getDynamics() {

        Session session = null;

        session = this.sessionFactory.getCurrentSession();
        Query query = session
                .createSQLQuery("SELECT COUNT(*) FROM SpyPath WHERE DATE(time)>=DATE_SUB(CURDATE(),INTERVAL 6 DAY) GROUP BY DATE(time) ORDER BY time;");

        List<Long> result = query.list();
        return result;

    }

Now I'm getting java.math.BigInteger cannot be cast to java.lang.Long . What's wrong?

Answer 1

Better option is use SQLQuery#addScalar than casting to Long or BigDecimal .

Here is modified query that returns count column as Long

Query query = session
             .createSQLQuery("SELECT COUNT(*) as count
                             FROM SpyPath 
                             WHERE DATE(time)>=DATE_SUB(CURDATE(),INTERVAL 6 DAY) 
                             GROUP BY DATE(time) 
                             ORDER BY time;")
             .addScalar("count", LongType.INSTANCE);

Then

List<Long> result = query.list(); //No ClassCastException here  

Related link

• Hibernate javadocs
• Scalar queries
• Hibernate.LONG , remember it has been deprecated since Hibernate version 3.6.X
  here is the deprecated document , so you have to use LongType.INSTANCE
• My previous answer

Answer 2

Your error might be in this line:

List<Long> result = query.list();

where query.list() is returning a BigInteger List instead of Long list. Try to change it to.

List<BigInteger> result = query.list();

Answer 3

尝试将 BigInteger 转换为这样的 long

Long longNumber= bigIntegerNumber.longValue();

Answer 4

I'm lacking context, but this is working just fine:

List<BigInteger> nums = new ArrayList<BigInteger>();
Long max = Collections.max(nums).longValue(); // from BigInteger to Long...

Answer 5

这是一个非常古老的帖子，但如果它对任何人都有好处，我们可以这样做：

Long max=((BigInteger) Collections.max(dynamics)).longValue(); 

Answer 6

You need to add an alias for the count to your query and then use the addScalar() method as the default for list() method in Hibernate seams to be BigInteger for numeric SQL types. Here is an example:

List<Long> sqlResult = session.createSQLQuery("SELECT column AS num FROM table")
    .addScalar("num", StandardBasicTypes.LONG).list();

Answer 7

Are you sure dynamics is a List<Long> and not List<BigInteger> ?

If dynamics is a List<Long> you don't need to do a cast to (Long)

Answer 8

想象一下 d.getId 是一个 Long，然后像这样包装：

BigInteger l  = BigInteger.valueOf(d.getId());

Answer 9

You need to retrieve the result as List of BigInteger then convert it to a Long collection.

List<BigInteger> ids = query.getResultList();
Set<Long> collect = ids.stream().map(id -> id.longValue()).collect(Collectors.toSet());