解决了的。请看下面我的答案。
在我的代码中，我试图重新Map键盘键。 z -> s . 我使用的是jna库5.6.0和jna平台5.6.0，但熟悉c语言的人也能理解我，因为jna使用的是user32和kernel32 dll中的winapi函数。
我的问题是newkey打印两次，在newkey之间出现oldkey。当我输入“z”时，它应该打印“s”，但它打印的是“szs”。
我的代码：

import com.sun.jna.Pointer;
import com.sun.jna.platform.win32.*;

public class ReMapper {

    private static WinUser.HHOOK hHook;
    final User32 user32Library = User32.INSTANCE;
    WinDef.HMODULE hMod = Kernel32.INSTANCE.GetModuleHandle(null);
    static WinUser.INPUT input = new WinUser.INPUT();

    public void reMapOn() {
        WinUser.LowLevelKeyboardProc keyboardHook = new WinUser.LowLevelKeyboardProc() {

            @Override
            public WinDef.LRESULT callback(int nCode, WinDef.WPARAM wParam, WinUser.KBDLLHOOKSTRUCT kbdllhookstruct) {
                if (nCode >= 0) {
                    switch (wParam.intValue()) {
                        case WinUser.WM_KEYUP:
                        case WinUser.WM_KEYDOWN:
                        case WinUser.WM_SYSKEYUP:
                        case WinUser.WM_SYSKEYDOWN:
                            if (kbdllhookstruct.vkCode == 90) {
                                sendKey(83);
                                break;
                            }
                        default:
                            wParam.setValue(WinUser.WM_SYSKEYDOWN);
                            break;
                    }
                }
                Pointer ptr = kbdllhookstruct.getPointer();
                long peer = Pointer.nativeValue(ptr);
                return user32Library.CallNextHookEx(hHook, nCode, wParam, new WinDef.LPARAM(peer));
            }
        };

        hHook = user32Library.SetWindowsHookEx(WinUser.WH_KEYBOARD_LL, keyboardHook, hMod, 0);

        int result;
        WinUser.MSG msg = new WinUser.MSG();
        while ((result = user32Library.GetMessage(msg, null, 0, 0)) != 0) {
            if (result == -1) {
                break;
            } else {
                user32Library.TranslateMessage(msg);
                user32Library.DispatchMessage(msg);
            }
        }
    }

    static void sendKey(int keyCode) {

        input.type = new WinDef.DWORD(WinUser.INPUT.INPUT_KEYBOARD);
        input.input.setType("ki"); // Because setting INPUT_INPUT_KEYBOARD is not enough: https://groups.google.com/d/msg/jna-users/NDBGwC1VZbU/cjYCQ1CjBwAJ
        input.input.ki.wScan = new WinDef.WORD(0);
        input.input.ki.time = new WinDef.DWORD(0);
        input.input.ki.dwExtraInfo = new BaseTSD.ULONG_PTR(0);
// Press
        input.input.ki.wVk = new WinDef.WORD(keyCode); // 0x41
        input.input.ki.dwFlags = new WinDef.DWORD(0);  // keydown

        User32.INSTANCE.SendInput(new WinDef.DWORD(1), (WinUser.INPUT[]) input.toArray(1), input.size());

// Release
        input.input.ki.wVk = new WinDef.WORD(keyCode); // 0x41
        input.input.ki.dwFlags = new WinDef.DWORD(2);  // keyup

        User32.INSTANCE.SendInput(new WinDef.DWORD(1), (WinUser.INPUT[]) input.toArray(1), input.size());
    }

    public static void main(String[] args) {
        new ReMapper().reMapOn();
    }
}

我的打印示例：

有人能帮我理解为什么会这样吗？