Below is the syntax highlighted version of DirectedEdge.java.

/****************************************************************************** * Compilation: javac DirectedEdge.java * Execution: java DirectedEdge * Dependencies: StdOut.java * * Immutable weighted directed edge. * ******************************************************************************/ package edu.princeton.cs.algs4; /** * The {@code DirectedEdge} class represents a weighted edge in an * {@link EdgeWeightedDigraph}. Each edge consists of two integers * (naming the two vertices) and a real-value weight. The data type * provides methods for accessing the two endpoints of the directed edge and * the weight. * <p> * For additional documentation, * see <a href="https://algs4.cs.princeton.edu/44sp">Section 4.4</a> of * <i>Algorithms, 4th Edition</i> by Robert Sedgewick and Kevin Wayne. * * @author Robert Sedgewick * @author Kevin Wayne */ public class DirectedEdge { private final int v; private final int w; private final double weight; /** * Initializes a directed edge from vertex {@code v} to vertex {@code w} with * the given {@code weight}. * @param v the tail vertex * @param w the head vertex * @param weight the weight of the directed edge * @throws IllegalArgumentException if either {@code v} or {@code w} * is a negative integer * @throws IllegalArgumentException if {@code weight} is {@code NaN} */ public DirectedEdge(int v, int w, double weight) { if (v < 0) throw new IllegalArgumentException("Vertex names must be non-negative integers"); if (w < 0) throw new IllegalArgumentException("Vertex names must be non-negative integers"); if (Double.isNaN(weight)) throw new IllegalArgumentException("Weight is NaN"); this.v = v; this.w = w; this.weight = weight; } /** * Returns the tail vertex of the directed edge. * @return the tail vertex of the directed edge */ public int from() { return v; } /** * Returns the head vertex of the directed edge. * @return the head vertex of the directed edge */ public int to() { return w; } /** * Returns the weight of the directed edge. * @return the weight of the directed edge */ public double weight() { return weight; } /** * Returns a string representation of the directed edge. * @return a string representation of the directed edge */ public String toString() { return v + "->" + w + " " + String.format("%5.2f", weight); } /** * Unit tests the {@code DirectedEdge} data type. * * @param args the command-line arguments */ public static void main(String[] args) { DirectedEdge e = new DirectedEdge(12, 34, 5.67); StdOut.println(e); } } /****************************************************************************** * Copyright 2002-2020, Robert Sedgewick and Kevin Wayne. * * This file is part of algs4.jar, which accompanies the textbook * * Algorithms, 4th edition by Robert Sedgewick and Kevin Wayne, * Addison-Wesley Professional, 2011, ISBN 0-321-57351-X. * http://algs4.cs.princeton.edu * * * algs4.jar is free software: you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation, either version 3 of the License, or * (at your option) any later version. * * algs4.jar is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with algs4.jar. If not, see http://www.gnu.org/licenses. ******************************************************************************/