1 /* 2 * Copyright (c) 2014, Oracle and/or its affiliates. All rights reserved. 3 * 4 * Redistribution and use in source and binary forms, with or without 5 * modification, are permitted provided that the following conditions 6 * are met: 7 * 8 * - Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 11 * - Redistributions in binary form must reproduce the above copyright 12 * notice, this list of conditions and the following disclaimer in the 13 * documentation and/or other materials provided with the distribution. 14 * 15 * - Neither the name of Oracle nor the names of its 16 * contributors may be used to endorse or promote products derived 17 * from this software without specific prior written permission. 18 * 19 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS 20 * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, 21 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 22 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR 23 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, 24 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, 25 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR 26 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF 27 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING 28 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS 29 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 30 */ 31 32 /* 33 * This source code is provided to illustrate the usage of a given feature 34 * or technique and has been deliberately simplified. Additional steps 35 * required for a production-quality application, such as security checks, 36 * input validation, and proper error handling, might not be present in 37 * this sample code. 38 */ 39 40 import java.security.SecureRandom; 41 import java.util.ArrayList; 42 import java.util.List; 43 import java.util.stream.IntStream; 44 45 /** 46 * Generates password of desired length. See {@link #usage} method 47 * for instructions and command line parameters. This sample shows usages of: 48 * <ul> 49 * <li>Method references.</li> 50 * <li>Lambda and bulk operations. A stream of random integers is mapped to 51 * chars, limited by desired length and printed in standard output as password 52 * string.</li> 53 * </ul> 54 * 55 */ 56 public class PasswordGenerator { 57 usage()58 private static void usage() { 59 System.out.println("Usage: PasswordGenerator LENGTH"); 60 System.out.println( 61 "Password Generator produces password of desired LENGTH."); 62 } 63 64 private static final List<Integer> PASSWORD_CHARS = new ArrayList<>(); 65 66 //Valid symbols. 67 static { 68 IntStream.rangeClosed('0', '9').forEach(PASSWORD_CHARS::add); // 0-9 69 IntStream.rangeClosed('A', 'Z').forEach(PASSWORD_CHARS::add); // A-Z 70 IntStream.rangeClosed('a', 'z').forEach(PASSWORD_CHARS::add); // a-z 71 } 72 73 /** 74 * The main method for the PasswordGenerator program. Run program with empty 75 * argument list to see possible arguments. 76 * 77 * @param args the argument list for PasswordGenerator. 78 */ main(String[] args)79 public static void main(String[] args) { 80 81 if (args.length != 1) { 82 usage(); 83 return; 84 } 85 86 long passwordLength; 87 try { 88 passwordLength = Long.parseLong(args[0]); 89 if (passwordLength < 1) { 90 printMessageAndUsage("Length has to be positive"); 91 return; 92 } 93 } catch (NumberFormatException ex) { 94 printMessageAndUsage("Unexpected number format" + args[0]); 95 return; 96 } 97 /* 98 * Stream of random integers is created containing Integer values 99 * in range from 0 to PASSWORD_CHARS.size(). 100 * The stream is limited by passwordLength. 101 * Valid chars are selected by generated index. 102 */ 103 new SecureRandom().ints(passwordLength, 0, PASSWORD_CHARS.size()) 104 .map(PASSWORD_CHARS::get) 105 .forEach(i -> System.out.print((char) i)); 106 } 107 printMessageAndUsage(String message)108 private static void printMessageAndUsage(String message) { 109 System.err.println(message); 110 usage(); 111 } 112 113 } 114