TreeMap和递归

Question

[更新]以下是我正在处理的程序，而不是像我需要的那样读出文件。图像是预期的输出。

String generate（）的辅助方法应该有助于递归文件：

这就是我的意思：

这是我的计划：

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


public class GrammarProcessor {

/* Rules for each nonterminal is stored in String[]  assoc. with key 
   TreeMap will store the keys in sorted order */ 
private Map<String, String[]> rules = new TreeMap<>();
private static final Random rnd = new Random(); 

/* Constructor */
public GrammarProcessor(List<String> grammar) {
    if (grammar == null || grammar.isEmpty()) {
        throw new IllegalArgumentException();
    } else {
        for (String element : grammar) {
            if (grammar.contains("::=")) { 
                String[] token = element.split("::="); // splits to key and value
                String left = token[0].trim(); 
                String right = token[1].trim();
                String[] split = right.split("[|]");
                rules.put(left, split);
            }
        }   
    }    
} // End of GrammarProcessor()

/* Method returns TRUE if the condition inside the if statement if symbol is equal
   to any of the specified strings, otherwise return FALSE */
public boolean grammarContains(String symbol) { // nonterminal symbols 
    return rules.containsKey(symbol); // return TRUE if symbol is in rules else FALSE
} // End of grammarContains() - Done 

/* Helper method for String generate() */
private String generate(String symbol, int n, String generated) {
    if (grammarContains(symbol) == false) {
        symbol += " ";
    } else {
        String[] array = rules.get(symbol);
        for (String element : array[rnd.nextInt(array.length)].trim().split("[ \t]+")) { 
            if (n != 0) {
                generated += element + " ";
                return generate(symbol, n-1, generated);
            } else {
                break;
            }
        }
    }
    return generated; 
}

/* Method returns nonterminal symbol */
public String getSymbols() {
    return rules.keySet().toString();
} // End of getSymbols()

public String generate(String symbol) {
    String generated = "";
    if (grammarContains(symbol) == false) { 
        throw new IllegalArgumentException(); 
    } else {
        String[] array = rules.get(symbol);
        for (String element : array[rnd.nextInt(array.length)].trim().split("[ \t]+")) {
            generated += element + "";
            symbol = element;
        }
    } 
    return generated; 
}

public String[] generate(String symbol, int times) {
    if (grammarContains(symbol) == false && times < 0) {
        throw new IllegalArgumentException();
    }
    String line = generate(symbol);
    String[] array = line.split(" ");
    return null ;
}

} // End of GrammarProcessor

这是我的测试程序：

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

public class GrammarTest {
public static void main(String[] args) throws IOException {
    Scanner console = new Scanner(System.in);

    // open grammar file
    Scanner input = new Scanner(new File("sentence1.txt"));

    // read the grammar file and construct the grammarProcessor
    List<String> grammar = new ArrayList<String>();
    while (input.hasNextLine()) {
        String nextRule = input.nextLine().trim();
        if (nextRule.length() > 0)
            grammar.add(nextRule);
    }
    GrammarProcessor processor = new GrammarProcessor(grammar);

    System.out.println(processor.getSymbols()); //test getSymbols()
    System.out.print("Which symbol do you want? ");
    String symbol = console.nextLine();
    if ( processor.grammarContains(symbol) ) //test grammarContains()
        System.out.println(processor.generate(symbol)); //test 
    else
        System.out.println(symbol + " not in grammar!");
   }
}