Java execution process – Rewriting methods execute first than constructors
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Java
I have the following code in the same java file
import javax.swing.SwingUtilities; import java.io.File; public class MainClass2{ public static void main(String[] args){ SwingUtilities.invokelater(new Runnable(){ public void run() { javax.swing.JFileChooser jfc = new MyFileChooser(); File file = jfc.getSelectedFile(); } }); } } class MyFileChooser extends javax.swing.JFileChooser{ public MyFileChooser(){ System.out.println("constructor call"); } @Override public java.io.File getSelectedFile(){ System.out.println("call to getSelectedFile"); return null; } }
When I run it, output it to me
Call getselectedfile
constructor call
Call getselectedfile
Should not output
constructor call
Call getselectedfile
I use Java 5
Solution
The constructor of myfilechooser is equivalent to:
public MyFileChooser() { super(); // *** System.out.println("constructor call"); }
The first call to getselectedfile () is created by the base class constructor of myfilechooser, which is in system out. Println ("constructor call") is implicitly called at a location marked * * *
This is a stack trace:
MyFileChooser.getSelectedFile() line: 16 AquaFileChooserUI.installComponents(JFileChooser) line: 1436 AquaFileChooserUI.installUI(JComponent) line: 122 MyFileChooser(JComponent).setUI(ComponentUI) line: 670 MyFileChooser(JFileChooser).updateUI() line: 1798 MyFileChooser(JFileChooser).setup(FileSystemView) line: 360 MyFileChooser(JFileChooser).<init>(File,FileSystemView) line: 333 MyFileChooser(JFileChooser).<init>() line: 286 MyFileChooser.<init>() line: 11
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