Below is the syntax highlighted version of Vector.java.

/****************************************************************************** * Compilation: javac Vector.java * Execution: java Vector * Dependencies: StdOut.java * * Implementation of a vector of real numbers. * * This class is implemented to be immutable: once the client program * initialize a Vector, it cannot change any of its fields * (d or data[i]) either directly or indirectly. Immutability is a * very desirable feature of a data type. * * % java Vector * x = [ 1.0 2.0 3.0 4.0 ] * y = [ 5.0 2.0 4.0 1.0 ] * z = [ 6.0 4.0 7.0 5.0 ] * 10z = [ 60.0 40.0 70.0 50.0 ] * |x| = 5.477225575051661 * <x, y> = 25.0 * * * Note that Vector is also the name of an unrelated Java library class * in the package java.util. * ******************************************************************************/ package edu.princeton.cs.algs4; /** * The {@code Vector} class represents a <em>d</em>-dimensional Euclidean vector. * Vectors are immutable: their values cannot be changed after they are created. * It includes methods for addition, subtraction, * dot product, scalar product, unit vector, Euclidean norm, and the Euclidean * distance between two vectors. * <p> * For additional documentation, * see <a href="https://algs4.cs.princeton.edu/12oop">Section 1.2</a> of * <i>Algorithms, 4th Edition</i> by Robert Sedgewick and Kevin Wayne. * * @author Robert Sedgewick * @author Kevin Wayne */ public class Vector { private int d; // dimension of the vector private double[] data; // array of vector's components /** * Initializes a d-dimensional zero vector. * * @param d the dimension of the vector */ public Vector(int d) { this.d = d; data = new double[d]; } /** * Initializes a vector from either an array or a vararg list. * The vararg syntax supports a constructor that takes a variable number of * arugments such as Vector x = new Vector(1.0, 2.0, 3.0, 4.0). * * @param a the array or vararg list */ public Vector(double... a) { d = a.length; // defensive copy so that client can't alter our copy of data[] data = new double[d]; for (int i = 0; i < d; i++) data[i] = a[i]; } /** * Returns the length of this vector. * * @return the dimension of this vector * @deprecated Replaced by {@link #dimension()}. */ @Deprecated public int length() { return d; } /** * Returns the dimension of this vector. * * @return the dimension of this vector */ public int dimension() { return d; } /** * Returns the dot product of this vector with the specified vector. * * @param that the other vector * @return the dot product of this vector and that vector * @throws IllegalArgumentException if the dimensions of the two vectors are not equal */ public double dot(Vector that) { if (this.d != that.d) throw new IllegalArgumentException("Dimensions don't agree"); double sum = 0.0; for (int i = 0; i < d; i++) sum = sum + (this.data[i] * that.data[i]); return sum; } /** * Returns the magnitude of this vector. * This is also known as the L2 norm or the Euclidean norm. * * @return the magnitude of this vector */ public double magnitude() { return Math.sqrt(this.dot(this)); } /** * Returns the Euclidean distance between this vector and the specified vector. * * @param that the other vector * @return the Euclidean distance between this vector and that vector * @throws IllegalArgumentException if the dimensions of the two vectors are not equal */ public double distanceTo(Vector that) { if (this.d != that.d) throw new IllegalArgumentException("Dimensions don't agree"); return this.minus(that).magnitude(); } /** * Returns the sum of this vector and the specified vector. * * @param that the vector to add to this vector * @return the vector whose value is {@code (this + that)} * @throws IllegalArgumentException if the dimensions of the two vectors are not equal */ public Vector plus(Vector that) { if (this.d != that.d) throw new IllegalArgumentException("Dimensions don't agree"); Vector c = new Vector(d); for (int i = 0; i < d; i++) c.data[i] = this.data[i] + that.data[i]; return c; } /** * Returns the difference between this vector and the specified vector. * * @param that the vector to subtract from this vector * @return the vector whose value is {@code (this - that)} * @throws IllegalArgumentException if the dimensions of the two vectors are not equal */ public Vector minus(Vector that) { if (this.d != that.d) throw new IllegalArgumentException("Dimensions don't agree"); Vector c = new Vector(d); for (int i = 0; i < d; i++) c.data[i] = this.data[i] - that.data[i]; return c; } /** * Returns the ith cartesian coordinate. * * @param i the coordinate index * @return the ith cartesian coordinate */ public double cartesian(int i) { return data[i]; } /** * Returns the scalar-vector product of this vector and the specified scalar * * @param alpha the scalar * @return the vector whose value is {@code (alpha * this)} * @deprecated Replaced by {@link #scale(double)}. */ @Deprecated public Vector times(double alpha) { Vector c = new Vector(d); for (int i = 0; i < d; i++) c.data[i] = alpha * data[i]; return c; } /** * Returns the scalar-vector product of this vector and the specified scalar * * @param alpha the scalar * @return the vector whose value is {@code (alpha * this)} */ public Vector scale(double alpha) { Vector c = new Vector(d); for (int i = 0; i < d; i++) c.data[i] = alpha * data[i]; return c; } /** * Returns a unit vector in the direction of this vector. * * @return a unit vector in the direction of this vector * @throws ArithmeticException if this vector is the zero vector */ public Vector direction() { if (this.magnitude() == 0.0) throw new ArithmeticException("Zero-vector has no direction"); return this.times(1.0 / this.magnitude()); } /** * Returns a string representation of this vector. * * @return a string representation of this vector, which consists of the * the vector entries, separates by single spaces */ public String toString() { StringBuilder s = new StringBuilder(); for (int i = 0; i < d; i++) s.append(data[i] + " "); return s.toString(); } /** * Unit tests the {@code Vector} data type. * * @param args the command-line arguments */ public static void main(String[] args) { double[] xdata = { 1.0, 2.0, 3.0, 4.0 }; double[] ydata = { 5.0, 2.0, 4.0, 1.0 }; Vector x = new Vector(xdata); Vector y = new Vector(ydata); StdOut.println(" x = " + x); StdOut.println(" y = " + y); Vector z = x.plus(y); StdOut.println(" z = " + z); z = z.times(10.0); StdOut.println(" 10z = " + z); StdOut.println(" |x| = " + x.magnitude()); StdOut.println(" <x, y> = " + x.dot(y)); StdOut.println("dist(x, y) = " + x.distanceTo(y)); StdOut.println("dir(x) = " + x.direction()); } } /****************************************************************************** * 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. ******************************************************************************/