Editor.java协助

Question

我有一个名为Editor.java的程序，它几乎完成但我需要完成public void doRun（String Line）。如何运行应该是当你键入RUN时它将启动程序在它可以找到的最低编号行执行。如果RUN后跟一个35之类的数字，它应该从它找到的大于或等于指定数字的第一个行号开始。例如，如果我输入：

5 LET A = 5
10 PRINT A
20 LET X = 10
30 LET Y = 20
40 PRINT X + Y
50 LET Z = X + Y * 2
60 PRINT Z
70 GOTO 90
80 LET Z = 10
90 PRINT X Y Z
100 LET P = 80
110 IF (Z > 20) THEN LET P = 10
120 PRINT P
RUN 15

输出应为：

X + Y = 30.0
Z : 50.0 
X Y Z : 10.0 20.0 50.0 
P : 10.0 

这是我迄今为止开发的代码如果有人可以提供帮助，我们将不胜感激。

import java.util.Scanner;
import java.io.*;

public class Editor
{
  EditLL list;
  HashTable commands;
  HashTable variables;
  final static String comm[] = {"LOAD", "SAVE", "RESEQUENCE", "LIST", "QUIT", "EXIT", "LET", "PRINT", "INPUT", "RUN"}; 

  public Editor()
  {
    list = new EditLL();
    commands = new HashTable();
    variables = new HashTable();
    for (int i = 0; i < comm.length; i++)
    {
      commands.insert(comm[i], (double)i);
    }
  }

  public boolean processLine(String line) throws IOException
  {
    boolean retval = true;
    line = trimLeadingWhitespace(line);
    int last = line.indexOf(' ');
    String initial = line;
    if (last >= 0)
      initial = line.substring(0, last);
    if (last >= 0)
    {
      line = line.substring(last);
      line = trimLeadingWhitespace(line);
    }
    else
      line = "";
    if (isInt(initial))
    {
      int lineNum = Integer.parseInt(initial);
      list.insert(lineNum, line);
    }
    else
    {
      int key = (int)commands.getValue(initial);
      switch(key)
      {
case 0: this.load(line);
        break;
case 1: this.save(line);
        break;
case 2: list.resequence(10);
        break;
case 3: System.out.println(this.list);
        break;
case 4:
case 5: retval = false;
        break;
case 6: doLet(line);  // line after the word let
        break;
case 7: print(line, variables);
        break;
case 8: input(line);
        break;
case 9: doRun(line);

default: System.out.println("Unknown command " + initial);
      }
    }
    return retval;
  }

  public void doRun(String line) // Need Help here
  {
    int linenum;
    int temp;
    line = trimLeadingWhitespace(line);
    line = trimTrailingWhitespace(line);
  }


  public void input(String line)
  {
    Scanner kb = new Scanner(System.in);

    line = trimLeadingWhitespace(line);
    line = trimTrailingWhitespace(line);
    System.out.print(line + "=?");
    variables.insert(line, kb.nextDouble());
  } 

  public void doLet(String line)
  {
    int last = line.indexOf('=');
    String lhs = line.substring(0, last);
    String lhs2 = "";
    int i = 0;
    char c = lhs.charAt(i);
    while(!Character.isWhitespace(c))
    {
      lhs2 += c;
      i++;
      c = lhs.charAt(i);
    }
    line = line.substring(last+1);
    double value = Infix.evaluate(line, variables);
    variables.insert(lhs2, value);
  }

  public void print(String line, HashTable variables)
  {
    line = trimLeadingWhitespace(line);
    double value = Infix.evaluate(line, variables);
    System.out.println(line + " = " + value);
  }


  public void load(String line) throws IOException
  {
    Scanner in = new Scanner(new File(line));
    list = new EditLL();
    int nextLine = 0;

    while(in.hasNext())
    {
      nextLine += 10;
      list.insert(nextLine, in.nextLine());
    }
    in.close();
  }

  public void save(String line) throws IOException
  {
    PrintWriter out = new PrintWriter(new File(line));
    String nextline = list.getFirst();
    while (!nextline.equals(""))
    {
      out.println(nextline);
      nextline = list.getNext();
    }
    out.close();
  }


  public static boolean isInt(String s)
  {
    boolean retval;
    try
    {
      Integer.parseInt(s);
      retval = true;
    }
    catch (NumberFormatException e)
    {
      retval = false;
    }
    return retval;
  } 

  public static String trimLeadingWhitespace(String s)
  {
    String retval = "";
    int i = 0;
    char c = s.charAt(i);
    while (Character.isWhitespace(c))
    {
      i++;
      c = s.charAt(i);
    } 
    for (int j = i; j < s.length(); j++)
    {
      retval += c = s.charAt(j);
    }

    return retval;
  }

  public static String trimTrailingWhitespace(String s)
  {
    String retval = "";

    int lastNonW = -1;
    char c;
    for (int j = 0; j < s.length(); j++)
    {
      c = s.charAt(j);
      if (!Character.isWhitespace(c))
      {
        lastNonW = j;
      }
    }

    for (int j = 0; j <= lastNonW; j++)
      retval += s.charAt(j);
    return retval;
  }
 public static void main(String args[]) throws IOException // Help Here
  {
    Editor ed = new Editor();
    Scanner kb = new Scanner(System.in);
    String line;

    do
    {

      line = kb.nextLine().toUpperCase();
    }while (ed.processLine(line));
  }
} 

Answer 1

你有更大的问题：你还没有实现GOTO。

如果你实现GOTO，那么你可以通过在指令列表的开头有一个0 GOTO 35的虚拟指令或者用户输入的任何内容来解决你的问题。

哦，一个合适的GOTO需要能够跳回来......

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