start() method doesn't exist

Question

This is my first multithreaded application and I'm having a bit of difficulty. I am making a new object called of class TextDistanceThread that implements Runnable but when I try to call start(), the editor tells me that no such method exists and the file won't compile. Here's my Driver class:

public class Driver {
    static float [][] results = new float[30][6];
    public static void main(String [] args) throws FileNotFoundException {

        Runnable [] threads = new TextDistanceThread[180];
        int threadCount = 0;

        for(int i = 0 ; i < 30 ; i++) {
            threads[threadCount] = new TextDistanceThread("Macbeth.txt", "Othello.txt", i, 0);
            threads[threadCount++].start();
            threads[threadCount] = new TextDistanceThread("Macbeth.txt", "HuckFinn.txt", i, 1);
            threads[threadCount++].start();
            threads[threadCount] = new TextDistanceThread("Macbeth.txt", "TomSawyer.txt", i, 2);
            threads[threadCount++].start();
            threads[threadCount] = new TextDistanceThread("Othello.txt", "HuckFinn.txt", i, 3);
            threads[threadCount++].start();
            threads[threadCount] = new TextDistanceThread("Othello.txt", "TomSawyer.txt", i, 4);
            threads[threadCount++].start();
            threads[threadCount] = new TextDistanceThread("TomSawyer.txt", "HuckFinn.txt", i, 5);
            threads[threadCount++].start();
        }
    }
}

and here's the TextDistanceThread class: public class TextDistanceThread implements Runnable {

    final int numTexts;
    Dictionary<String, Integer>[] texts;
    Dictionary<String, Float>[] normalized;
    float difference;
    int [] lengths;
    int row, col;

    public TextDistanceThread(String file1, String file2, int row, int col) throws FileNotFoundException {
        numTexts = 2;
        texts = new Dictionary[numTexts];
        normalized = new Dictionary[numTexts];
        for (int text = 0 ; text < numTexts ; text++) {
            texts[text] = new Dictionary<String, Integer>();
            normalized[text] = new Dictionary<String, Float>();
        }
        difference = 0;
        lengths = new int[numTexts];
        this.row = row;
        this.col = col;

        //Read file into dictionary without punctuation
        if(new File(file1).exists()) {System.out.println("File " + file1 + " found");}
        Scanner text = new Scanner(new File(file1));
        while (text.hasNext()) {
            lengths[0]++;
            String temp = text.next().toLowerCase().replaceAll("(?!\')\\p{Punct}", "");
            if (!texts[0].add(temp, 1)) {
                texts[0].set(temp, texts[0].lookup(temp) + 1);
            }
        }

        if(new File(file2).exists()) {System.out.println("File " + file2 + " found");}
        text = new Scanner(new File(file2));
        while (text.hasNext()) {
            lengths[1]++;
            String temp = text.next().toLowerCase().replaceAll("(?!\')\\p{Punct}", "");
            if (!texts[1].add(temp, 1)) {
                texts[1].set(temp, texts[1].lookup(temp) + 1);
            }
        }
    }

    public void run() {

        System.out.println("Normalizing:");
        //Normalize dictionaries
        for(int i = 0 ; i < numTexts ; i++) {
            texts[i].reset();
            normalized[i].add((String) texts[i].getCurrentPair().getKey(), (float)texts[i].getCurrent() / lengths[i]);

            while(texts[i].hasNext()) {
                texts[i].next();
                normalized[i].add((String) texts[i].getCurrentPair().getKey(), (float)texts[i].getCurrent() / lengths[i]);
            }
        }

        //Find the difference
        texts[0].reset();

        System.out.println("Cross-checking:");
        while(normalized[0].hasNext()) {
            if(normalized[1].contains(normalized[0].getCurrentPair().getKey())) {
                difference += Math.abs(normalized[0].getCurrent() - normalized[1].lookup((String)normalized[0].getCurrentPair().getKey()));
                //System.out.println(normalized[0].getCurrentPair() + Float.toString(Math.abs(normalized[0].getCurrent() - normalized[1].lookup((String) normalized[0].getCurrentPair().getKey()))));
                normalized[1].remove(normalized[0].getCurrentPair().getKey());
                normalized[0].remove();
                normalized[0].reset();
            }
            else {
                normalized[0].next();
            }
        }

        System.out.println("Adding:");
        for(int i = 0 ; i < numTexts ; i++) {
            normalized[i].reset();
            difference += normalized[i].getCurrent();
            //System.out.println(normalized[i].getCurrentPair() + Float.toString(normalized[i].getCurrent()));
            while(normalized[i].hasNext()) {
                difference += Math.abs(normalized[i].getNext());
                //System.out.println(normalized[i].getCurrentPair() + Float.toString(normalized[i].getCurrent()));
            }
        }

        Driver.results[row][col] = difference;
    }
}

I tried googling all over the place and no one else seems to be having this problem. I'm convinced I'm missing something terribly obvious.

In addition is there anything I should know about scheduling?

Answer 1

The Runnable interface doesn't declare the start() method. That is why you can't call it.

The standard way of starting a thread with a Runnable is to pass the Runnable instance to a Thread, and call start() on the Thread.

Create an array of Threads, create the Threads with your Runnables, and then call start() on those Threads.

Thread[] threads = new Thread[180];

E.g.

threads[threadCount] = new Thread(
    new TextDistanceThread("Macbeth.txt", "Othello.txt", i, 0));

The JVM takes care of scheduling threads for you; you don't need to worry about scheduling them.