boolean next() throwsMoves the cursor forward one row from its current position. A ResultSet cursor is initially positioned before the first row; the first call to the method next makes the first row the current row; the second call makes the second row the current row, and so on.
When a call to the next method returns false, the cursor is positioned after the last row. Any invocation of a ResultSet method which requires a current row will result in a SQLException being thrown. If the result set type is TYPE_FORWARD_ONLY, it is vendor specified whether their JDBC driver implementation will return false or throw an SQLException on a subsequent call to next.
If an input stream is open for the current row, a call to the method next will implicitly close it. A ResultSet object's warning chain is cleared when a new row is read.
Returns: true if the new current row is valid; false if there are no more rows Throws: SQLException - if a database access error occurs or this method is called on a closed result set 翻译如下： boolean next() throws SQLException 将当前行从上一行移到下一行。一个 ResultSet的当前行最初指向第一行查询结果前。当第一次调用next的时候，当前行将会指向第一行查询结果。第二次调用就会指向第二行查询结果，等等。 当调用next方法返回false的时候，当前行当前行指向最后一行查询结果之后。这时候，任何ResultSet 的请求当前行的方法调用都会导致SQLException 被抛出。但如果查询的结果设置为TYPE_FORWARD_ONLY，next方法在这时候根据实现厂商的不同，可能会返回false也坑能会抛出SQLException 异常 的警告将会被清楚。
Statement statement = conn.createStatement();
ResultSet res = statement.executeQuery(selectSql);
if (!res.next()) {
//res is null
} else {
// res is not null
}
ResultSet res = ...使用某种方法获取查询结果
int nRow = 0;
while(res.next()) {
++nRow;
}
res.beforeFirst();
// 其他代码不变
ResultSet res = ...使用某种方法获取查询结果 res.last(); final int nRow = res.getRow(); res.beforeFirst(); // 其他代码不变