java - 线程中的异常 "main"java.lang.ArrayIndexOutOfBoundsException : 3 at AdjMatrixDigraph. main(AdjMatrixDigraph.java:90)

Question

在我的代码中，我试图导出邻接矩阵，但出现以下异常。

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 3
    at AdjMatrixDigraph.main(AdjMatrixDigraph.java:90)

AdjMatrixDigraph.java

import java.util.Iterator;
import java.util.NoSuchElementException;


public class AdjMatrixDigraph extends StdOut {
    private int V;
    private int E;
    private boolean[][] adj;

    // empty graph with V vertices
    public AdjMatrixDigraph(int V) {
        if (V < 0) throw new RuntimeException("Number of vertices must be nonnegative");
        this.V = V;
        this.E = 0;
        this.adj = new boolean[V][V];
    }

    // random graph with V vertices and E edges
    public AdjMatrixDigraph(int V, int E) {
        this(V);
        if (E < 0) throw new RuntimeException("Number of edges must be nonnegative");
        if (E > V*V) throw new RuntimeException("Too many edges");

        // can be inefficient
        while (this.E != E) {
            int v = (int) (V * Math.random());
            int w = (int) (V * Math.random());
            addEdge(v, w);
        }
    }

    // number of vertices and edges
    public int V() { return V; }
    public int E() { return E; }


    // add directed edge v->w
    public void addEdge(int v, int w) {
        if (!adj[v][w]) E++;
        adj[v][w] = true;
    }

    // return list of neighbors of v
    public Iterable<Integer> adj(int v) {
        return new AdjIterator(v);
    }

    // support iteration over graph vertices
    private class AdjIterator implements Iterator<Integer>, Iterable<Integer> {
        private int v, w = 0;
        AdjIterator(int v) { this.v = v; }

        public Iterator<Integer> iterator() { return this; }

        public boolean hasNext() {
            while (w < V) {
                if (adj[v][w]) return true;
                w++;
            }
            return false;
        }

        public Integer next() {
            if (hasNext()) { return w++;                         }
            else           { throw new NoSuchElementException(); }
        }

        public void remove()  { throw new UnsupportedOperationException();  }
    }


    // string representation of Graph - takes quadratic time
    public String toString() {
        String NEWLINE = System.getProperty("line.separator");
        StringBuilder s = new StringBuilder();
        s.append(V + " " + E + NEWLINE);
        for (int v = 0; v < V; v++) {
            s.append(v + ": ");
            for (int w : adj(v)) {
                s.append(w + " ");
            }
            s.append(NEWLINE);
        }
        return s.toString();
    }


    // test client
    public static void main(String[] args) {
        int V = Integer.parseInt(args[3]);
        int E = Integer.parseInt(args[1]);
        AdjMatrixDigraph G = new AdjMatrixDigraph(V, E);
        StdOut.println(G);
    }

}

标准输出.java

import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.io.UnsupportedEncodingException;
import java.util.Locale;

/**
 *  <i>Standard output</i>. This class provides methods for writing strings
 *  and numbers to standard output.
 *  <p>
 *  For additional documentation, see <a href="http://introcs.cs.princeton.edu/15inout">Section 1.5</a> of
 *  <i>Introduction to Programming in Java: An Interdisciplinary Approach</i> by Robert Sedgewick and Kevin Wayne.
 */
public  class StdOut {

    // force Unicode UTF-8 encoding; otherwise it's system dependent
    public static final String charsetName = "UTF-8";

    // assume language = English, country = US for consistency with StdIn
    private static final Locale US_LOCALE = new Locale("en", "US");

    // send output here
    private static PrintWriter out;

    // this is called before invoking any methods
    static {
        try {
            out = new PrintWriter(new OutputStreamWriter(System.out, charsetName), true);
        }
        catch (UnsupportedEncodingException e) { System.out.println(e); }
    }

    // don't instantiate
    public StdOut() { 


    }

    // close the output stream (not required)
   /**
     * Close standard output.
     */
    public static void close() {
        out.close();
    }

   /**
     * Terminate the current line by printing the line separator string.
     */
    public static void println() {
        out.println();
    }

   /**
     * Print an object to standard output and then terminate the line.
     */
    public static void println(Object x) {
        out.println(x);
    }

   /**
     * Print a boolean to standard output and then terminate the line.
     */
    public static void println(boolean x) {
        out.println(x);
    }

   /**
     * Print a char to standard output and then terminate the line.
     */
    public static void println(char x) {
        out.println(x);
    }

   /**
     * Print a double to standard output and then terminate the line.
     */
    public static void println(double x) {
        out.println(x);
    }

   /**
     * Print a float to standard output and then terminate the line.
     */
    public static void println(float x) {
        out.println(x);
    }

   /**
     * Print an int to standard output and then terminate the line.
     */
    public static void println(int x) {
        out.println(x);
    }

   /**
     * Print a long to standard output and then terminate the line.
     */
    public static void println(long x) {
        out.println(x);
    }

   /**
     * Print a short to standard output and then terminate the line.
     */
    public static void println(short x) {
        out.println(x);
    }

   /**
     * Print a byte to standard output and then terminate the line.
     */
    public static void println(byte x) {
        out.println(x);
    }

   /**
     * Flush standard output.
     */
    public static void print() {
        out.flush();
    }

   /**
     * Print an Object to standard output and flush standard output.
     */
    public static void print(Object x) {
        out.print(x);
        out.flush();
    }

   /**
     * Print a boolean to standard output and flush standard output.
     */
    public static void print(boolean x) {
        out.print(x);
        out.flush();
    }

   /**
     * Print a char to standard output and flush standard output.
     */
    public static void print(char x) {
        out.print(x);
        out.flush();
    }

   /**
     * Print a double to standard output and flush standard output.
     */
    public static void print(double x) {
        out.print(x);
        out.flush();
    }

   /**
     * Print a float to standard output and flush standard output.
     */
    public static void print(float x) {
        out.print(x);
        out.flush();
    }

   /**
     * Print an int to standard output and flush standard output.
     */
    public static void print(int x) {
        out.print(x);
        out.flush();
    }

   /**
     * Print a long to standard output and flush standard output.
     */
    public static void print(long x) {
        out.print(x);
        out.flush();
    }

   /**
     * Print a short to standard output and flush standard output.
     */
    public static void print(short x) {
        out.print(x);
        out.flush();
    }

   /**
     * Print a byte to standard output and flush standard output.
     */
    public static void print(byte x) {
        out.print(x);
        out.flush();
    }

   /**
     * Print a formatted string to standard output using the specified
     * format string and arguments, and flush standard output.
     */
    public static void printf(String format, Object... args) {
        out.printf(US_LOCALE, format, args);
        out.flush();
    }

   /**
     * Print a formatted string to standard output using the specified
     * locale, format string, and arguments, and flush standard output.
     */
    public static void printf(Locale locale, String format, Object... args) {
        out.printf(locale, format, args);
        out.flush();
    }

    // This method is just here to test the class
    public static void main(String[] args) {

        // write to stdout
        StdOut.println("Test");
        StdOut.println(17);
        StdOut.println(true);
        StdOut.printf("%.6f\n", 1.0/7.0);
    }

}

Answer 1

第 90 行是 int V = Integer.parseInt(args[3]);。检查如何传递/解析命令行参数(第一个参数是 args[0]，第二个参数是 args[1]，等等)。