Java tutorial
//package com.java2s; import java.awt.Dimension; import java.awt.Point; import java.awt.Window; public class Main { /** * Center the given <code>windows</code> in relative to the given <code>invoker</code>. * @param invoker Reference window for the window to center. * @param window The window instance to center. */ public static void centerOnWindow(Window invoker, Window window) { Point invokerLocationOnScreen = invoker.getLocationOnScreen(); Dimension invokerSize = invoker.getSize(); Dimension windowSize = window.getSize(); window.setLocation(invokerLocationOnScreen.x + (invokerSize.width / 2) - (windowSize.width / 2), invokerLocationOnScreen.y + ((invokerSize.height / 2) - (windowSize.height / 2) / 2)); } }