blocks|key|533821|text|你也可以这样做：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|533822|rs.last();
int+numberOfRows+=+rs.getRow();
if(numberOfRows)+{
++++rs.beforeFirst();
++++while(rs.next())+{
++++++++...
++++}
}|code-block|syntax|javascript|533823|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

You can do this too:

<pre><code>rs.last();
int numberOfRows = rs.getRow();
if(numberOfRows) {
 rs.beforeFirst();
 while(rs.next()) {
 ...
 }
}
</code></pre>

blocks|key|533834|text|我通常使用的模式如下：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|533835|boolean+empty+=+true;
while(+rs.next()+)+{
++++//+ResultSet+processing+here
++++empty+=+false;
}

if(+empty+)+{
++++//+Empty+result+set
}|code-block|syntax|javascript|533836|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

The pattern I normally use is as follows:

<pre><code>boolean empty = true;
while( rs.next() ) {
 // ResultSet processing here
 empty = false;
}

if( empty ) {
 // Empty result set
}
</code></pre>

blocks|key|2030073|text|+while+(results.next())|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|2030074|用于迭代结果，如果结果为空，set.so+results.next()将返回false。|unstyled|2030075|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$B|C]]|$1|D|3|E|5|F|7|J|8|@]|9|@]|A|$]]|$1|G|3|-4|5|F|7|K|8|@]|9|@]|A|$]]]|H|$]]

<pre><code> while (results.next())
</code></pre>

is used to iterate over a result set.so results.next() will return false if its empty.

blocks|key|3437927|text|下面是一个简单的方法：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3437928|public+static+boolean+isResultSetEmpty(ResultSet+resultSet)+{
++++return+!resultSet.first();
}|code-block|syntax|javascript|3437929|注意事项|3437930|这会将光标移动到开头。但是，如果您只是想测试它是否为空，那么您可能还没有对它做任何事情。|3437931|另一个选择|3437932|在进行任何处理之前，请立即使用first()方法。SELECT+rs+=+stat.executeQuery("SELECT+*+from+ResultSet+WHERE+is_query_processed+=+0;")；|offset|length|style|CODE|3437933|if(rs.first())+{
++++//+there's+stuff+to+do
}+else+{
++++//+rs+was+empty
}|3437934|参考文献|3437935|ResultSet+(Java+Platform+SE+6)|3437936|entityMap|0|LINK|mutability|MUTABLE|url|http://java.sun.com/javase/6/docs/api/java/sql/ResultSet.html#first()^0|0|0|0|0|0|F|7|0|0|0|0|U|0|0^^$0|@$1|2|3|4|5|6|7|16|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|17|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|18|8|@]|9|@]|A|$]]|$1|I|3|J|5|6|7|19|8|@]|9|@]|A|$]]|$1|K|3|L|5|6|7|1A|8|@]|9|@]|A|$]]|$1|M|3|N|5|6|7|1B|8|@$O|1C|P|1D|Q|R]]|9|@]|A|$]]|$1|S|3|T|5|D|7|1E|8|@]|9|@]|A|$E|F]]|$1|U|3|V|5|6|7|1F|8|@]|9|@]|A|$]]|$1|W|3|X|5|6|7|1G|8|@]|9|@$O|1H|P|1I|1|1J]]|A|$]]|$1|Y|3|-4|5|6|7|1K|8|@]|9|@]|A|$]]]|Z|$10|$5|11|12|13|A|$14|15]]]]

Here's a simple method to do it:

<pre><code>public static boolean isResultSetEmpty(ResultSet resultSet) {
 return !resultSet.first();
}
</code></pre>

<h3>Caveats</h3>

This moves the cursor to the beginning. But if you just want to test whether it's empty, you probably haven't done anything with it yet anyways.

<h3>Alternatively</h3>

Use the <code>first()</code> method immediately, before doing any processing.
 ResultSet rs = stat.executeQuery("SELECT * from table WHERE is_query_processed = 0;");

<pre><code>if(rs.first()) {
 // there's stuff to do
} else {
 // rs was empty
}
</code></pre>

<h3>References</h3>

<a href="http://java.sun.com/javase/6/docs/api/java/sql/ResultSet.html#first()" rel="nofollow noreferrer">ResultSet (Java Platform SE 6)</a>

blocks|key|3437970|text|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3437971|为什么执行没有进入while循环？|blockquote|3437972|3437973|3437974|如果ResultSet为空，则rs.next()方法将返回false，并且无论rs.getRow()返回多少行数(而不是count)，都不会进入while循环体。Colins的例子是可行的。|offset|length|style|CODE|3437975|entityMap^0|0|0|0|0|F|9|13|B|0^^$0|@$1|2|3|-4|4|5|6|N|7|@]|8|@]|9|$]]|$1|A|3|B|4|C|6|O|7|@]|8|@]|9|$]]|$1|D|3|-4|4|5|6|P|7|@]|8|@]|9|$]]|$1|E|3|-4|4|5|6|Q|7|@]|8|@]|9|$]]|$1|F|3|G|4|5|6|R|7|@$H|S|I|T|J|K]|$H|U|I|V|J|K]]|8|@]|9|$]]|$1|L|3|-4|4|5|6|W|7|@]|8|@]|9|$]]]|M|$]]

<blockquote>
 Why is execution not entering the
 while loop?
</blockquote>

If your ResultSet is empty the <code>rs.next()</code> method returns false and the body of the while loop isn't entered regardless to the rownumber (not count) <code>rs.getRow()</code> returns. Colins example works.

blocks|key|2030228|text|来回移动游标以确定行数不是正常的JDBC实践。通常的做法是将ResultSet映射到值对象的List，每个值对象表示一个表行实体，然后使用List方法确定是否有行。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|2030229|例如：|2030230|List<User>+users+=+userDAO.list();

if+(users.isEmpty())+{
++++//+It+is+empty!
if+(users.size()+==+1)+{
++++//+It+has+only+one+row!
}+else+{
++++//+It+has+more+than+one+row!
}|code-block|syntax|javascript|2030231|其中，list()方法如下所示：|2030232|public+List<User>+list()+throws+SQLException+{
++++Connection+connection+=+null;
++++Statement+statement+=+null;
++++ResultSet+resultSet+=+null;
++++List<User>+users+=+new+ArrayList<User>();

++++try+{
++++++++connection+=+database.getConnection();
++++++++statement+=+connection.createStatement();
++++++++resultSet+=+statement.executeQuery(SQL_LIST);
++++++++while+(resultSet.next())+{
++++++++++++User+user+=+new+User();
++++++++++++user.setId(resultSet.getLong("id"));
++++++++++++user.setName(resultSet.getString("name"));
++++++++++++//+...
++++++++++++users.add(user);
++++++++}
++++}+finally+{
++++++++if+(resultSet+!=+null)+try+{+resultSet.close();+}+catch+(SQLException+logOrIgnore)+{}
++++++++if+(statement+!=+null)+try+{+statement.close();+}+catch+(SQLException+logOrIgnore)+{}
++++++++if+(connection+!=+null)+try+{+connection.close();+}+catch+(SQLException+logOrIgnore)+{}
++++}

++++return+users;
}|2030233|另请参阅this+answer以获取其他JDBC示例。|2030234|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/questions/1813858/sqlite-3-jdbc-driver-throws-resultsset-closed-exception-on-empty-resultset/1814443#1814443^0|U|9|1A|4|1X|4|0|0|0|3|6|0|0|4|B|0|0^^$0|@$1|2|3|4|5|6|7|10|8|@$9|11|A|12|B|C]|$9|13|A|14|B|C]|$9|15|A|16|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|17|8|@]|D|@]|E|$]]|$1|H|3|I|5|J|7|18|8|@]|D|@]|E|$K|L]]|$1|M|3|N|5|6|7|19|8|@$9|1A|A|1B|B|C]]|D|@]|E|$]]|$1|O|3|P|5|J|7|1C|8|@]|D|@]|E|$K|L]]|$1|Q|3|R|5|6|7|1D|8|@]|D|@$9|1E|A|1F|1|1G]]|E|$]]|$1|S|3|-4|5|6|7|1H|8|@]|D|@]|E|$]]]|T|$U|$5|V|W|X|E|$Y|Z]]]]

Shifting the cursor forth and back to determine the amount of rows is not the normal JDBC practice. The normal JDBC practice is to map the <code>ResultSet</code> to a <code>List</code> of value objects each representing a table row entity and then just use the <code>List</code> methods to determine if there are any rows.

For example:

<pre><code>List&lt;User&gt; users = userDAO.list();

if (users.isEmpty()) {
 // It is empty!
if (users.size() == 1) {
 // It has only one row!
} else {
 // It has more than one row!
}
</code></pre>

where the <code>list()</code> method look like as follows:

<pre><code>public List&lt;User&gt; list() throws SQLException {
 Connection connection = null;
 Statement statement = null;
 ResultSet resultSet = null;
 List&lt;User&gt; users = new ArrayList&lt;User&gt;();

 try {
 connection = database.getConnection();
 statement = connection.createStatement();
 resultSet = statement.executeQuery(SQL_LIST);
 while (resultSet.next()) {
 User user = new User();
 user.setId(resultSet.getLong("id"));
 user.setName(resultSet.getString("name"));
 // ...
 users.add(user);
 }
 } finally {
 if (resultSet != null) try { resultSet.close(); } catch (SQLException logOrIgnore) {}
 if (statement != null) try { statement.close(); } catch (SQLException logOrIgnore) {}
 if (connection != null) try { connection.close(); } catch (SQLException logOrIgnore) {}
 }

 return users;
}
</code></pre>

Also see <a href="https://stackoverflow.com/questions/1813858/sqlite-3-jdbc-driver-throws-resultsset-closed-exception-on-empty-resultset/1814443#1814443">this answer</a> for other JDBC examples.

blocks|key|2030243|text|CLOSE_CURSORS_AT_COMMIT|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2030244|公共静态final+int+CLOSE_CURSORS_AT_COMMIT|2030245|The+constant+indicating+that+ResultSet+objects+should+be+closed+when+the+method+Connection.commit+is+called.+|code-block|syntax|javascript|2030246|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|L|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|M|8|@]|9|@]|A|$G|H]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

CLOSE_CURSORS_AT_COMMIT

public static final int CLOSE_CURSORS_AT_COMMIT

<pre><code>The constant indicating that ResultSet objects should be closed when the method Connection.commit is called. 
</code></pre>

blocks|key|1281183|text|试试这个：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1281184|ResultSet+MyResult+=+null;
MyResult+=+Conexion.createStatement().executeQuery("Your+Query++Here!!!");
MyResult.last();
int+NumResut+=+MyResult.getRow();MyResult.beforeFirst();
//Follow+with+your+other+operations....|code-block|syntax|javascript|1281185|这样你就可以正常工作了。|1281186|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

Try with this:

<pre><code>ResultSet MyResult = null;
MyResult = Conexion.createStatement().executeQuery("Your Query Here!!!");
MyResult.last();
int NumResut = MyResult.getRow();MyResult.beforeFirst();
//Follow with your other operations....
</code></pre>

This manner you'll be able work normally.

blocks|key|1277851|text|也许你可以将你的结果集对象转换成字符串对象，并检查它是否为空。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1277852|`if(resultset.toString().isEmpty()){
+++++//+containg+null+result
+}
+else{
+++++//This+conains+the+result+you+want
+}`|code-block|syntax|javascript|1277853|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

May be you can convert your resultset object into String object and check whether is it empty or not.

<pre><code>`if(resultset.toString().isEmpty()){
 // containg null result
 }
 else{
 //This conains the result you want
 }`
</code></pre>

blocks|key|533990|text|这将检查它是否为空，同时不跳过第一条记录|type|unstyled|depth|inlineStyleRanges|entityRanges|data|533991|if+(rs.first())+{
++++do+{
++++++++//+ResultSet+is+not+empty,+Iterate+over+it
++++}+while+(rs.next());
}+else+{
++++//+ResultSet+is+empty
}|code-block|syntax|javascript|533992|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

This checks if it's empty or not while not skipping the first record

<pre><code>if (rs.first()) {
 do {
 // ResultSet is not empty, Iterate over it
 } while (rs.next());
} else {
 // ResultSet is empty
}
</code></pre>

<pre><code>Class.forName("org.sqlite.JDBC");
Connection conn =
 DriverManager.getConnection("jdbc:sqlite:userdata.db");
Statement stat = conn.createStatement();

ResultSet rs = stat.executeQuery("SELECT * from table WHERE is_query_processed = 0;");

int rowcount = rs.getRow(); 
System.out.println("Row count = "+rowcount); // output 1

rs.first(); // This statement generates an exception
</code></pre>

Why is it so?

How to find out if a Java ResultSet obtained is empty?

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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Class.forName("org.sqlite.JDBC");Connection conn =    DriverManager.getConnection("jdbc:sqlite:userdata.db");Statement stat = conn.createStatement();ResultSet r...

问如何判断获取的Java ResultSet是否为空？
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问如何判断获取的Java ResultSet是否为空？EN