密码生成器

Question

我正在尝试创建一个创建密码的 Java 程序，密码可以是全小写、小写和大写、小写和大写和数字、小写和大写、数字和标点符号，并且该程序还必须创建其中一个密码用户选择并且必须根据用户选择的内容生成密码长度。我已经生成了供用户选择的密码选项，并提示他选择一个。我现在被困在如何创建上面提到的密码类型上。有人建议我使用 ASCII 值，然后将它们转换为文本。我知道如何将它们转换为文本，但它会显示数字、字母和标点符号。有什么方法可以只为小写字母生成 ASCII 值吗？另外，我将如何根据用户提供的长度生成密码？

Answer 1

我使用这个不可变类。
它使用构建器模式。
不支持扩展。

public final class PasswordGenerator {

    private static final String LOWER = "abcdefghijklmnopqrstuvwxyz";
    private static final String UPPER = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
    private static final String DIGITS = "0123456789";
    private static final String PUNCTUATION = "!@#$%&*()_+-=[]|,./?><";
    private boolean useLower;
    private boolean useUpper;
    private boolean useDigits;
    private boolean usePunctuation;

    private PasswordGenerator() {
        throw new UnsupportedOperationException("Empty constructor is not supported.");
    }

    private PasswordGenerator(PasswordGeneratorBuilder builder) {
        this.useLower = builder.useLower;
        this.useUpper = builder.useUpper;
        this.useDigits = builder.useDigits;
        this.usePunctuation = builder.usePunctuation;
    }

    public static class PasswordGeneratorBuilder {

        private boolean useLower;
        private boolean useUpper;
        private boolean useDigits;
        private boolean usePunctuation;

        public PasswordGeneratorBuilder() {
            this.useLower = false;
            this.useUpper = false;
            this.useDigits = false;
            this.usePunctuation = false;
        }

        /**
         * Set true in case you would like to include lower characters
         * (abc...xyz). Default false.
         *
         * @param useLower true in case you would like to include lower
         * characters (abc...xyz). Default false.
         * @return the builder for chaining.
         */
        public PasswordGeneratorBuilder useLower(boolean useLower) {
            this.useLower = useLower;
            return this;
        }

        /**
         * Set true in case you would like to include upper characters
         * (ABC...XYZ). Default false.
         *
         * @param useUpper true in case you would like to include upper
         * characters (ABC...XYZ). Default false.
         * @return the builder for chaining.
         */
        public PasswordGeneratorBuilder useUpper(boolean useUpper) {
            this.useUpper = useUpper;
            return this;
        }

        /**
         * Set true in case you would like to include digit characters (123..).
         * Default false.
         *
         * @param useDigits true in case you would like to include digit
         * characters (123..). Default false.
         * @return the builder for chaining.
         */
        public PasswordGeneratorBuilder useDigits(boolean useDigits) {
            this.useDigits = useDigits;
            return this;
        }

        /**
         * Set true in case you would like to include punctuation characters
         * (!@#..). Default false.
         *
         * @param usePunctuation true in case you would like to include
         * punctuation characters (!@#..). Default false.
         * @return the builder for chaining.
         */
        public PasswordGeneratorBuilder usePunctuation(boolean usePunctuation) {
            this.usePunctuation = usePunctuation;
            return this;
        }

        /**
         * Get an object to use.
         *
         * @return the {@link gr.idrymavmela.business.lib.PasswordGenerator}
         * object.
         */
        public PasswordGenerator build() {
            return new PasswordGenerator(this);
        }
    }

    /**
     * This method will generate a password depending the use* properties you
     * define. It will use the categories with a probability. It is not sure
     * that all of the defined categories will be used.
     *
     * @param length the length of the password you would like to generate.
     * @return a password that uses the categories you define when constructing
     * the object with a probability.
     */
    public String generate(int length) {
        // Argument Validation.
        if (length <= 0) {
            return "";
        }

        // Variables.
        StringBuilder password = new StringBuilder(length);
        Random random = new Random(System.nanoTime());

        // Collect the categories to use.
        List<String> charCategories = new ArrayList<>(4);
        if (useLower) {
            charCategories.add(LOWER);
        }
        if (useUpper) {
            charCategories.add(UPPER);
        }
        if (useDigits) {
            charCategories.add(DIGITS);
        }
        if (usePunctuation) {
            charCategories.add(PUNCTUATION);
        }

        // Build the password.
        for (int i = 0; i < length; i++) {
            String charCategory = charCategories.get(random.nextInt(charCategories.size()));
            int position = random.nextInt(charCategory.length());
            password.append(charCategory.charAt(position));
        }
        return new String(password);
    }
}

这是一个用法示例，

PasswordGenerator passwordGenerator = new PasswordGenerator.PasswordGeneratorBuilder()
        .useDigits(true)
        .useLower(true)
        .useUpper(true)
        .build();
String password = passwordGenerator.generate(8); // output ex.: lrU12fmM 75iwI90o