Sample application that uses JEP 454: Foreign Function & Memory API to create simple text UI with ncurses. Demo: https://gist.github.com/plamentotev/fff031eca3722df792db86096e238d02?permalink_comment_id=5043190#gistcomment-5043190

HelloWorld.java

import java.lang.foreign.Arena;
import java.lang.foreign.FunctionDescriptor;
import java.lang.foreign.Linker;
import java.lang.foreign.SymbolLookup;
import java.lang.foreign.ValueLayout;
import java.lang.invoke.MethodHandle;

public class HelloWorld {
    public static void main(String[] args) throws Throwable {
        // Arena handles the lifecycle of native memory segments.
        // There are different implementations, the confined one would
        // free the memory after the try-with-resources completes 
        try(var arena = Arena.ofConfined()) {
            // See below for the implementation, but NCurses is utility
            // class initialized with MethodHandle instances for the
            // ncurses functions we need.
            var ncurses = new NCurses(arena);

            // Once we have MethodHandle for foreign function, we can call by invoking `invoke`.
            // The return value is the return value of the function.
            // In this case a pointer to the main window.
            var mainWindow = ncurses.initscr.invoke();
            ncurses.noecho.invoke();
            // Remember `mainWindow` from above? `wprintw` accepts pointer to a window
            // (`mainWindow` in this case) and pointer to a string.
            // Allocating array of chars and passing the pointer is trivial - just call 
            // `Arena#allocateFrom` and it will allocate it on the native memory segment
            // and return a pointer you can pass to the `invoke` method.
            ncurses.wprintw.invoke(mainWindow, arena.allocateFrom("Press "));
            ncurses.wattron.invoke(mainWindow, NCurses.A_STANDOUT);
            ncurses.wprintw.invoke(mainWindow, arena.allocateFrom("q"));
            ncurses.wattroff.invoke(mainWindow, NCurses.A_STANDOUT);
            ncurses.wprintw.invoke(mainWindow, arena.allocateFrom(" to quit"));
            ncurses.wrefresh.invoke(mainWindow);

            // If the foreign function accepts int, double, etc. you can just pass the
            // primitive value, no need to do anything special for those.
            var msgWindow = ncurses.newwin.invoke(5, 25, 5, 30);
            ncurses.box.invoke(msgWindow, 0, 0);
            ncurses.wmove.invoke(msgWindow, 2, 6);
            ncurses.wprintw.invoke(msgWindow, arena.allocateFrom("Hello, "));
            ncurses.wattron.invoke(msgWindow, NCurses.A_UNDERLINE);
            ncurses.wprintw.invoke(msgWindow, arena.allocateFrom("World"));
            ncurses.wattroff.invoke(msgWindow, NCurses.A_UNDERLINE);
            ncurses.wprintw.invoke(msgWindow, arena.allocateFrom("!"));
            ncurses.wrefresh.invoke(msgWindow);

            ncurses.wmove.invoke(mainWindow, 0, 15);

            int ch;
            do {
                ch = (int) ncurses.getch.invoke();
            } while (ch != 'q');

            ncurses.delwin.invoke(mainWindow);
            ncurses.endwin.invoke();
        }
    }
}

final class NCurses {
    // We'll see how those are used below
    private final SymbolLookup ncurses;
    private final Linker linker;

    // Some ncurses related constants. Unfortunately there is no way to get those
    // form the native library.
    static final int A_STANDOUT = 65536;
    static final int A_UNDERLINE = 131072;

    // MethodHandle for the functions that we need for the demo 
    final MethodHandle initscr;
    final MethodHandle wprintw;
    final MethodHandle wrefresh;
    final MethodHandle getch;
    final MethodHandle endwin;
    final MethodHandle noecho;
    final MethodHandle wattron;
    final MethodHandle wattroff;
    final MethodHandle newwin;
    final MethodHandle delwin;
    final MethodHandle box;
    final MethodHandle wmove;

    NCurses(Arena arena) {
        // This is where to look for the ncurses symbols.
        // Unfortunately the library name is platform dependant:
        // calling `libraryLookup` with only `libncurses` would fail.
        // And on Windows obviously the library has `dll` extension,
        // so calling with `libncurses.so.6` would fail on Windows.
        ncurses = SymbolLookup.libraryLookup("libncurses.so.6", arena);
        linker = Linker.nativeLinker();

        // FunctionDescriptor describes the function signature. With the function name
        // and the descriptor we can acquire MethodHandle for it. Which in turn is used to call the function.
        // See `initFunction` below.
        // Notice that the first parameter for `FunctionDescriptor.of` is the return type,
        // the rest are the function arguments.
        initscr = initFunction("initscr", FunctionDescriptor.of(ValueLayout.ADDRESS));
        wprintw = initFunction("wprintw", FunctionDescriptor.of(ValueLayout.JAVA_INT,
            ValueLayout.ADDRESS, ValueLayout.ADDRESS));
        wrefresh = initFunction("wrefresh", FunctionDescriptor.of(ValueLayout.JAVA_INT,
            ValueLayout.ADDRESS));
        getch = initFunction("getch", FunctionDescriptor.of(ValueLayout.JAVA_INT));
        endwin = initFunction("endwin", FunctionDescriptor.of(ValueLayout.JAVA_INT));
        noecho = initFunction("noecho", FunctionDescriptor.of(ValueLayout.JAVA_INT));
        wattron = initFunction("wattron", FunctionDescriptor.of(ValueLayout.JAVA_INT,
            ValueLayout.ADDRESS, ValueLayout.JAVA_INT));
        wattroff = initFunction("wattroff", FunctionDescriptor.of(ValueLayout.JAVA_INT,
            ValueLayout.ADDRESS, ValueLayout.JAVA_INT));
        newwin = initFunction("newwin", FunctionDescriptor.of(ValueLayout.ADDRESS,
            ValueLayout.JAVA_INT, ValueLayout.JAVA_INT, ValueLayout.JAVA_INT, ValueLayout.JAVA_INT));
        delwin = initFunction("attroff", FunctionDescriptor.of(ValueLayout.JAVA_INT, ValueLayout.ADDRESS));
        box = initFunction("box", FunctionDescriptor.of(ValueLayout.JAVA_INT,
            ValueLayout.ADDRESS, ValueLayout.JAVA_INT, ValueLayout.JAVA_INT));
        wmove = initFunction("wmove", FunctionDescriptor.of(ValueLayout.JAVA_INT,
                ValueLayout.ADDRESS, ValueLayout.JAVA_INT, ValueLayout.JAVA_INT));
    }

    // To acquire MethodHandle for foreign function all we need is the name and the descriptor (the function signature)
    private MethodHandle initFunction(String functionName, FunctionDescriptor descriptor) {
        var functionAddress = ncurses.find(functionName).orElseThrow();

        return linker.downcallHandle(functionAddress, descriptor);
    }
}

Demo:

demo.mp4