вывод только определенных System.property

build.gradle

@@ -13,3 +13,19 @@ repositories {
     mavenLocal()
     mavenCentral()
 }
+
+ext {
+    libs_dir = 'libs'
+    jline_version = '3.14.1'
+}
+
+dependencies {
+    compile group: 'org.jline', name: 'jline',                version: jline_version
+    compile group: 'org.jline', name: 'jline-terminal-jansi', version: jline_version
+}
+
+task copyDeps(type: Copy) {
+    into project.buildDir.toPath().resolve('libs').resolve(libs_dir)
+    from configurations.runtime
+}
+jar.dependsOn(copyDeps)

src/main/java/mc/server/Main.java

@@ -1,8 +1,48 @@
 package mc.server;
 
+import mc.server.shell.CommandService;
+import mc.server.shell.CommandServiceImpl;
+import mc.server.shell.SystemPropertiesCommand;
+import org.jline.builtins.CommandRegistry;
+import org.jline.reader.*;
+
+import java.io.PrintWriter;
+
 public class Main {
 
     public static void main(String[] args) {
-        System.out.println("hello?");
+        System.out.println("mc-server");
+
+        CommandService commandService = new CommandServiceImpl();
+        commandService.register("system-properties", new SystemPropertiesCommand());
+
+        final Completer completer = CommandRegistry.compileCompleters(commandService);
+
+        final LineReader reader = LineReaderBuilder.builder()
+                .completer(completer)
+                .build();
+
+        try {
+            final CommandRegistry.CommandSession session = new CommandRegistry.CommandSession(reader.getTerminal());
+            final PrintWriter terminalWriter = reader.getTerminal().writer();
+            //noinspection InfiniteLoopStatement
+            while (true) {
+                final String line = reader.readLine().trim();
+
+                final ParsedLine parsedLine = reader.getParser().parse(line, 0);
+                final String commandName = parsedLine.word();
+                final String[] argv = parsedLine.words().subList(1, parsedLine.words().size()).toArray(new String[0]);
+
+                if (commandService.hasCommand(commandName)) {
+                    commandService.execute(session, commandName, argv);
+                }
+
+                terminalWriter.println("line = " + String.join(", ", parsedLine.words()));
+            }
+        } catch (UserInterruptException ignore) {
+            // ignore
+        } catch (Exception e) {
+            e.printStackTrace();
+        }
     }
 }

src/main/java/mc/server/shell/Command.java

@@ -0,0 +1,8 @@
+package mc.server.shell;
+
+import org.jline.builtins.Builtins;
+
+public interface Command {
+
+    void execute(Builtins.CommandInput commandInput);
+}

src/main/java/mc/server/shell/CommandService.java

@@ -0,0 +1,8 @@
+package mc.server.shell;
+
+import org.jline.builtins.CommandRegistry;
+
+public interface CommandService extends CommandRegistry {
+
+    void register(String commandName, Command command);
+}

src/main/java/mc/server/shell/CommandServiceImpl.java

@@ -0,0 +1,57 @@
+package mc.server.shell;
+
+import org.jline.builtins.Builtins;
+import org.jline.builtins.Builtins.CommandMethods;
+import org.jline.builtins.Completers.SystemCompleter;
+import org.jline.reader.impl.completer.NullCompleter;
+
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Set;
+
+public class CommandServiceImpl implements CommandService {
+
+    private final Map<String, CommandMethods> commands = new HashMap<>();
+
+    public void register(String commandName, Command command) {
+        commands.put(commandName, new CommandMethods(
+                command::execute,
+                cmdName -> Collections.singletonList(NullCompleter.INSTANCE)
+        ));
+    }
+
+    public Object execute(CommandSession session, String command) {
+        return execute(session, command, new String[0]);
+    }
+
+    @Override
+    public Object execute(CommandSession session, String command, String[] args) {
+        commands.get(command).execute().accept(new Builtins.CommandInput(command, args, session));
+        return null;
+    }
+
+    @Override
+    public Set<String> commandNames() {
+        return commands.keySet();
+    }
+
+    @Override
+    public Map<String, String> commandAliases() {
+        return Collections.emptyMap();
+    }
+
+    @Override
+    public boolean hasCommand(String commandName) {
+        return commands.containsKey(commandName);
+    }
+
+    @Override
+    public SystemCompleter compileCompleters() {
+        final SystemCompleter systemCompleter = new SystemCompleter();
+        systemCompleter.addAliases(commandAliases());
+        commands.forEach((commandName, command) -> systemCompleter.add(commandName, NullCompleter.INSTANCE));
+
+        return systemCompleter;
+    }
+}

src/main/java/mc/server/shell/SystemPropertiesCommand.java

@@ -0,0 +1,28 @@
+package mc.server.shell;
+
+import org.jline.builtins.Builtins.CommandInput;
+
+import java.io.PrintWriter;
+import java.util.Arrays;
+import java.util.List;
+import java.util.Map;
+import java.util.stream.Stream;
+
+public class SystemPropertiesCommand implements Command {
+
+    @Override
+    public void execute(CommandInput input) {
+        final PrintWriter writer = input.terminal().writer();
+        Stream<Map.Entry<Object, Object>> stream = System.getProperties().entrySet().stream();
+
+        if (input.args().length > 0) {
+            final List<String> argv = Arrays.asList(input.args());
+            stream = stream.filter(entry -> {
+                //noinspection SuspiciousMethodCalls
+                return argv.contains(entry.getKey());
+            });
+        }
+
+        stream.forEach(entry -> writer.printf("%s = %s\n", entry.getKey(), entry.getValue().toString()));
+    }
+}