SendInput.java

import com.sun.jna.platform.win32.User32;
import com.sun.jna.platform.win32.WinDef;
import com.sun.jna.platform.win32.WinUser;
import com.sun.jna.Native;
import com.sun.jna.platform.win32.Kernel32;

public class InputSender {

    public static void main(String[] args) {
        int processId = 1234; // Replace with your target process ID
        WinDef.HWND hwnd = findWindowByProcessId(processId);
        if (hwnd != null) {
            User32.INSTANCE.SetForegroundWindow(hwnd);
            sendKeys("Hello from Java!");
            moveMouse(100, 200);  // Move mouse to coordinates (100, 200)
            clickMouse();         // Perform a mouse click
        } else {
            System.out.println("Window not found!");
        }
    }

    public static void setWindowPosition(WinDef.HWND hwnd, int x, int y, int width, int height) {
        // SWP_NOZORDER maintains the window's z-order position
        User32.INSTANCE.SetWindowPos(hwnd, null, x, y, width, height, WinUser.SWP_NOZORDER);
    }

    private static WinDef.HWND findWindowByProcessId(int processId) {
        final WinDef.HWND[] result = {null};
        User32.INSTANCE.EnumWindows((hwnd, pointer) -> {
            byte[] windowText = new byte[512];
            User32.INSTANCE.GetWindowTextA(hwnd, windowText, 512);
            int[] pid = new int[1];
            User32.INSTANCE.GetWindowThreadProcessId(hwnd, pid);
            if (pid[0] == processId) {
                result[0] = hwnd;
                return false; // Stop enumeration
            }
            return true; // Continue enumeration
        }, null);
        return result[0];
    }

    private static void sendKeys(String data) {
        for (char c : data.toCharArray()) {
            short vk = (short) Character.toUpperCase(c);
            User32.INSTANCE.keybd_event(vk, (byte) 0, WinUser.KEYBD_EVENTF_KEYDOWN, null);
            try {
                Thread.sleep(10); // small pause between key presses
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            User32.INSTANCE.keybd_event(vk, (byte) 0, WinUser.KEYBD_EVENTF_KEYUP, null);
        }
    }

    private static void moveMouse(int x, int y) {
        User32.INSTANCE.SetCursorPos(x, y);
    }

    private static void clickMouse() {
        User32.INSTANCE.mouse_event(WinUser.MOUSEEVENTF_LEFTDOWN, 0, 0, 0, null);
        User32.INSTANCE.mouse_event(WinUser.MOUSEEVENTF_LEFTUP, 0, 0, 0, null);
    }
}