public void setSpecifications(ObservableList<Specifications> data) {
String sql = "select * from specifications where ( bid=" + bid[0] + " or bid=" + bid[1] + " or bid=" + bid[2] + " or bid=" + bid[3] + " ) and ( mid=" + mid[0] + " or mid=" + mid[1] + " or mid=" + mid[2] + " or mid=" + mid[3] + " ) and ( vid=" + vid[0] + " or vid=" + vid[1] + " or vid=" + vid[2] + " or vid=" + vid[3] + " );";
int colCount = 0;
String specVal[], paramVal = null;
specVal = new String[]{" ", " ", " ", " "};
try {
stmt = conn.createStatement();
rs = stmt.executeQuery(sql);
rsmd = rs.getMetaData();
colCount = rsmd.getColumnCount();
for (int colIndex = 0; colIndex < colCount; colIndex++) {
rs.beforeFirst();
paramVal=rsmd.getColumnName(colIndex+1);
for (int rowIndex = 0; rs.next(); rowIndex++) {
specVal[rowIndex] = rs.getString(paramVal);
}
data.add(new Specifications(paramVal, specVal[0], specVal[1], specVal[2], specVal[3]));
//**NullPointerException**
}
} catch (SQLException ex) {
Logger.getLogger(Compare.class.getName()).log(Level.SEVERE, null, ex);
}
}
堆栈跟踪:
java.lang.NullPointerException
file:<path>.jar!/carshowroomsystem/details/compare/Compare.fxml
at carshowroomsystem.dataInterface.Compare.setSpecifications(Compare.java:138)
at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:69)
at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:217)
at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:170)
... rest of the trace
Caused by: java.lang.NullPointerException
at carshowroomsystem.dataInterface.Compare.setSpecifications(Compare.java:138)
at carshowroomsystem.details.compare.CompareController.addCar(CompareController.java:74)
at carshowroomsystem.details.compare.CompareController.initialize(CompareController.java:65)
at javafx.fxml.FXMLLoader.load(FXMLLoader.java:2152)
at javafx.fxml.FXMLLoader.load(FXMLLoader.java:2028)
at carshowroomsystem.WelcomeController.handleCompareAction(WelcomeController.java:106)
... 44 more
它在 data.add(...)
行抛出 NullPointerException
,我已经检查了所有参数是否具有一定的值!不知道该怎么办。
为什么跟踪显示 Compare.fxml
文件?它应该是 .java
最佳答案
您有String specVal[], paramVal = null;
它初始化 paramVal
为空。表达式paramVal=rsmd.getColumnName(colIndex+1)
位于 for
的第三部分表达式,因此它是在迭代之后执行的,因此第一次迭代使用 null
paramVal
的值。您需要重写代码,因为它没有意义,并了解如何for
语句在 Java 中有效。
关于java - NullPointerException:在不期望的地方抛出,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/21836087/