java - java中 vector 的使用

Question

我一直在研究这个问题，它涉及到马尔可夫链算法在java中的实现。当我为变量 r 分配 vector 元素的值时，它给了我一个错误。 (第 54 行)。错误显示为“需要数组但找到了 java.unit.Vector”。代码粘贴在下面。

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

class Chain {
    static final int NPREF = 2;    // size of prefix
    static final String NONWORD = "\n";
                    // "word" that can't appear
    Hashtable statetab = new Hashtable(); 
                    // key = Prefix, value = suffix Vector
    Prefix prefix = new Prefix(NPREF, NONWORD);
                    // initial prefix
    //Random rand = new Random();

// Chain build: build State table from input stream
void build(BufferedReader in) throws IOException
{
    StreamTokenizer st = new StreamTokenizer(in);

    st.resetSyntax();                     // remove default rules
    st.wordChars(0, Character.MAX_VALUE); // turn on all chars
    st.whitespaceChars(0, ' ');           // except up to blank
    while (st.nextToken() != st.TT_EOF)
        add(st.sval);
    add(NONWORD);
}

// Chain add: add word to suffix list, update prefix
void add(String word)
{
    Vector suf = (Vector) statetab.get(prefix);
    if (suf == null) {
        suf = new Vector();
        statetab.put(new Prefix(prefix), suf);
    }
    suf.addElement(word);
    prefix.pref.removeElementAt(0);
    prefix.pref.addElement(word);
}

// Chain generate: generate output words
void generate(int nwords, PrintWriter out, Vector <Integer> random_num)
{
    prefix = new Prefix(NPREF, NONWORD);
    for (int i = 0; i < nwords; i++) {
        Vector s = (Vector) statetab.get(prefix);
        if (s == null) {
            System.err.println("Markov: internal error: no state");
            System.exit(1);
        }

        final int r = (random_num.get(i) % s.size());
        String suf = (String) s.elementAt(r);
        if (suf.equals(NONWORD))
            break;
        out.println(suf);
        prefix.pref.removeElementAt(0);
        prefix.pref.addElement(suf);
    }
}
}

class Prefix {
    public Vector pref;    // NPREF adjacent words from input
static final int MULTIPLIER = 31;    // for hashCode()

// Prefix constructor: duplicate existing prefix
Prefix(Prefix p)
{
    pref = (Vector) p.pref.clone();
}

// Prefix constructor: n copies of str
Prefix(int n, String str)
{
    pref = new Vector();
    for (int i = 0; i < n; i++)
        pref.addElement(str);
}

// Prefix hashCode: generate hash from all prefix words
public int hashCode()
{
    int h = 0;

    for (int i = 0; i < pref.size(); i++)
        h = MULTIPLIER * h + pref.elementAt(i).hashCode();
    return h;
}

// Prefix equals: compare two prefixes for equal words
public boolean equals(Object o)
{
    Prefix p = (Prefix) o;

    for (int i = 0; i < pref.size(); i++)
        if (!pref.elementAt(i).equals(p.pref.elementAt(i)))
            return false;
    return true;
}

}

class Markov {
    static final int MAXGEN = 10000; // maximum words generated
        static Vector <Integer> random_num = new Vector <Integer>();

        static BufferedReader random_reader;
    public static void main(String[] args) throws IOException
    {            

                                 BufferedReader in = new BufferedReader (new FileReader ("../alice30.txt"));
                                 PrintWriter out = new PrintWriter (new FileWriter ("../output/markov_java_out.txt"));             
                                 BufferedReader random_reader = new BufferedReader (new FileReader ("../random_num.txt"));
                                 String s;
                                 s= random_reader.readLine();
                                 while(s != null)
                                 {
                                         int element = Integer.parseInt(s.trim());
                                         random_num.addElement(new Integer(element));
                                         s = random_reader.readLine();
                                 }

        Chain chain = new Chain();
        int nwords = MAXGEN;

        chain.build(in);

                in.close();
        chain.generate(nwords,out, random_num);
                out.close();
    }
}

Answer 1

您是说 random_num.elementAt(i) 吗？