问题描述
我正在尝试创建一个带有文本和图像的 JFrame 窗口。但是,我不断收到空指针异常。这是我的代码,有人可以帮忙吗?没有什么很复杂的,这只是给我一个例子。谢谢!
import pyspark.sql.functions as F
df2 = df.groupBy('id','tran_date').agg(
F.coalesce(
F.max(F.when(F.col('effc_date') < F.col('tran_date'),F.col('effc_date'))),F.min(F.when(F.col('effc_date') >= F.col('tran_date'),F.col('effc_date')))
).alias('effc_date')
)
df2.show()
+---+----------+----------+
| id| tran_date| effc_date|
+---+----------+----------+
| 12|2020-02-01|2019-02-01|
| 34|2020-02-01|2020-02-15|
| 40|2020-02-01|2019-02-15|
+---+----------+----------+
我收到的错误如下:
import java.awt.FlowLayout; // specifies how comments are arranged
import javax.swing.JFrame; // provides basic window features
import javax.swing.JLabel; // displays text and images
import javax.swing.SwingConstants; // common constants used with Swing
import javax.swing.Icon; // interface used to manipulate images
import javax.swing.ImageIcon; // loads images
class LabelFrame extends JFrame{
private final JLabel label1; // JLabel with just text
private final JLabel label2; // JLabel constructed with text and icon
private final JLabel label3; // JLabel with added text and icon
// LabelFrame constructor adds JLabels to JFrame
LabelFrame() {
super("Testing label");
setLayout(new FlowLayout()); // set frame layout
// JLabel constructor with a string argument
label1 = new JLabel("Label with text");
label1.setToolTipText("This is label1");
add(label1); // add label1 to JFrame
// JLabel constructor with string,Icon and alignment arguments
Icon bug = new ImageIcon(getClass().getResource("bug1.png"));
label2 = new JLabel("Label with text and icon",bug,SwingConstants.LEFT);
label2.setToolTipText("This is label2");
add(label2); // add labe2 to JFrame
label3 = new JLabel(); // JLabel constructor with no arguments
label3.setText("Label with icon and text at botton");
label3.setHorizontalTextPosition(SwingConstants.CENTER);
label3.setVerticalTextPosition(SwingConstants.BottOM);
label3.setToolTipText("This is label3");
add(label3); // add label3 to JFrame
}
}
public class LabelTest {
public static void main(String[] args) {
LabelFrame labelFrame = new LabelFrame();
labelFrame.setDefaultCloSEOperation(JFrame.EXIT_ON_CLOSE);
labelFrame.setSize(260,180);
labelFrame.setVisible(true);
}
}
解决方法
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