Explain invokeAndWait and invokeLater
In Java Swing, invokeAndWait() and invokeLater() are methods used to execute code on the Event Dispatch Thread (EDT), which is the thread responsible for managing user interface events and updates. While both methods achieve the same goal of executing code on the EDT, they differ in their timing and whether they block the calling thread.
Table of Contents
Explanation
1. invokeAndWait()
- InvokeAndWait() is a static method defined in the SwingUtilities class.
- It is used to execute a task on the EDT and wait for its completion before allowing the calling thread to proceed.
- This method invokeAndWait and invokeLater is typically used when you need to perform a task on the EDT and wait for it to finish before continuing with the rest of the program execution.
- invokeAndWait() is useful for tasks that require immediate updates to the UI or synchronization with other threads.
2. invokeLater()
- Â invokeLater() is also a static method defined in the SwingUtilities class.
- Â It is used to execute a task on the EDT asynchronously, without blocking the calling thread.
- Â This method is typically used when you need to perform a task on the EDT but do not need to wait for its completion before continuing with the rest of the program execution.
- Â invokeLater() is useful for tasks that update the UI or perform other operations that should not block the calling thread.
java
import javax.swing.*;
public class InvokeAndWaitVsInvokeLaterExample {
public static void main(String[] args) {
// Example using invokeAndWait()
try {
SwingUtilities.invokeAndWait(() -> {
// Code executed on the EDT
JFrame frame = new JFrame("invokeAndWait Example");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setSize(200, 200);
frame.setVisible(true);
});
} catch (Exception e) {
e.printStackTrace();
}
// Example using invokeLater()
SwingUtilities.invokeLater(() -> {
// Code executed on the EDT
JFrame frame = new JFrame("invokeLater Example");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setSize(200, 200);
frame.setVisible(true);
});
}
}
In this example, we demonstrate the usage of both invokeAndWait and invokeLater methods to create and display Swing frames (JFrame). The invokeAndWait() method is used to create a frame and wait for its creation to finish before proceeding, ensuring that the frame is fully initialized before continuing. On the other hand, the invokeLater() method is used to create a frame asynchronously, allowing the program to continue executing without waiting for the frame creation to complete. Both methods achieve the same result of creating and displaying a frame on the EDT but differ in their timing and blocking behavior.