Add Utils.waitForClose

runtime/Java/src/org/antlr/v4/runtime/misc/Utils.java

@@ -30,6 +30,9 @@
 
 package org.antlr.v4.runtime.misc;
 
+import java.awt.Window;
+import java.awt.event.WindowAdapter;
+import java.awt.event.WindowEvent;
 import java.io.BufferedWriter;
 import java.io.FileWriter;
 import java.io.IOException;
@@ -82,4 +85,36 @@ public class Utils {
 		w.write(content);
 		w.close();
 	}
+
+	public static void waitForClose(final Window window) throws InterruptedException {
+		final Object lock = new Object();
+
+		Thread t = new Thread() {
+			@Override
+			public void run() {
+				synchronized (lock) {
+					while (window.isVisible()) {
+						try {
+							lock.wait(500);
+						} catch (InterruptedException e) {
+						}
+					}
+				}
+			}
+		};
+
+		t.start();
+
+		window.addWindowListener(new WindowAdapter() {
+			@Override
+			public void windowClosing(WindowEvent arg0) {
+				synchronized (lock) {
+					window.setVisible(false);
+					lock.notify();
+				}
+			}
+		});
+
+		t.join();
+	}
 }