java中如何处理表列中的空值?
在从数据库表中获取值时,我一次又一次地获取空指针异常…为什么它会给我空指针异常 这是我的密码:java中如何处理表列中的空值?,java,jdbc,nullpointerexception,Java,Jdbc,Nullpointerexception,在从数据库表中获取值时,我一次又一次地获取空指针异常…为什么它会给我空指针异常 这是我的密码: private HashSet getPlayerList() { HashSet hs = new HashSet(); String soccername = ""; try { conn = ConnectionProvider.getConnection(); rs = null;
private HashSet getPlayerList() {
HashSet hs = new HashSet();
String soccername = "";
try {
conn = ConnectionProvider.getConnection();
rs = null;
pstmt = null;
String sql = "Select * from Players where deleted = false";
if (conn != null) {
pstmt = conn.prepareStatement(sql);
rs = pstmt.executeQuery();
while (rs.next()) {
soccername = rs.getString("soccername").trim();// this line giving exception
if (soccername == null || soccername.isEmpty()) {
soccername = rs.getString("name").trim();
}
hs.add(soccername);
}
}
} catch (NamingException ex) {
System.out.println(ex);
} catch (SQLException ex) {
System.out.println(ex);
} finally {
try {
pstmt.close();
rs.close();
conn.close();
} catch (SQLException ex) {
System.out.println(ex);
}
}
return hs;
}
这是错误的:
soccername = rs.getString("soccername").trim();// this line giving exception
if (soccername == null || soccername.isEmpty()) {
如果rs.getStringsoccername返回null,则必须导致NPE,因为它后面跟着函数trim
更好的是:
soccername = rs.getString("soccername");
if (soccername == null || soccername.trim().isEmpty()) {
应该是:
soccername = rs.getString("soccername");
if (soccername == null || soccername.isEmpty()) {
soccername = rs.getString("name").trim();
} else {
//now you are sure that soccername is not null
soccername = soccername.trim();
}
可能重复的