我的任务就是在爪哇 编程一条指挥线

s 意指测试编译器的部件。 您可以看到一个可以打字的命令, 如“ 读源 ” 、 “ 分隔 ” 、 “ 建设_ ast ” 、 “ ast2cfg ” 、 “ print_ cfg ” 等。

爪哇有任何图书馆可以帮助我建立翻译(或翻译?) 。 I know a python 模块可以做我想做的事 : cmd

我写了类似的东西自己:

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.Arrays;
import java.util.HashMap;

interface Command {
    public abstract void action(String[] parameters);
}

public class Repl {
    private String prompt = "
$ ";

    private HashMap<String, Command> commands;

    private Command nullCommand = null;

    private Command defaultCommand = null;

    public Repl() {
        commands = new HashMap<String, Command>();
    }

    public void setPrompt(String prompt) {
        this.prompt = prompt;
    }

    public void setDefaultCommand(Command defaultCommand) {
        this.defaultCommand = defaultCommand;
    }

    public void setNullCommand(Command nullCommand) {
        this.nullCommand = nullCommand;
    }

    public void addCommand(String name, Command command) {
        commands.put(name, command);
    }

    public void runRepl() {

        if (nullCommand == null) {
            System.err.println("There is no  nullCommand  specified");
            return;
        }
        if (defaultCommand == null) {
            System.err.println("There is no  defaultCommand  specified");
            return;
        }

        try {
            BufferedReader reader = new BufferedReader(new InputStreamReader(
                    System.in));

            String commandName;
            String[] parameters;

            while (true) {
                System.out.print(prompt);

                commandName = reader.readLine();

                if (commandName == null) {
                    nullCommand.action(null);
                } else {
                    parameters = commandName.trim().split("\s+");

                    Command com = commands.get(parameters[0]);
                    if (com != null) {
                        com.action(parameters);
                    } else {
                        defaultCommand.action(parameters);
                    }
                }
            }

        } catch (Exception e) {
            e.printStackTrace();
            System.err.println("Internal error within compiler: stopping compilation");
            System.exit(1);
        }
    }

    /**
     * Exapmpe:
     */
    public static void main(String[] args) {
        Repl repl = new Repl();

        repl.addCommand("printparams", new Command() {
            @Override
            public void action(String[] parameters) {
                System.out.println(Arrays.toString(parameters));
            }
        });

        repl.addCommand("add", new Command() {
            @Override
            public void action(String[] parameters) {
                if (parameters.length == 3) { // {"add", "2", "3"}
                    try {
                        int x = Integer.parseInt(parameters[1]);
                        int y = Integer.parseInt(parameters[2]);
                        System.out.println("Ergebnis: " + (x + y));
                    } catch (NumberFormatException e) {
                        System.out.println("Arguments have to be integers");
                    }
                } else {
                    System.out.println("There have to be two arguments");
                }
            }
        });

        Command helpcommand = new Command() {
            @Override
            public void action(String[] parameters) {
                System.out.println("There is:  help ,  printparams [PARAMS...] ,  exit  and  add INTEGER INTEGER ");
            }
        };
        repl.addCommand("help", helpcommand);
        repl.setDefaultCommand(helpcommand);

        Command exitcommand = new Command() {
            @Override
            public void action(String[] parameters) {
                System.out.println("Bye!");
                System.exit(0);
            }
        };
        repl.addCommand("exit", exitcommand);
        repl.setNullCommand(exitcommand);

        repl.runRepl();
    }
}

使用模式,例如“使用:加上INTEGER InTEGER[INTEGER...] ”等使用模式,以便根据参数的剖析方式产生两个以上数字,这样,添加新命令并确保它们始终一致的工作就更少了。

我还在问自己,这是否设计过头了。你建议这样写一个循环吗?

while(true) {
    String command = getUserInput();
    if (command.equals("dothis")) {
        dothis1();
        someMember = dothis2();
    } else if (command.equals("dothat"))
        dothat();
    } else {
        printHelp();
    }
}