Move RandomStringUtils

src/main/java/fr/xephi/authme/util/RandomStringUtils.java

@@ -0,0 +1,63 @@
+package fr.xephi.authme.util;
+
+import java.security.SecureRandom;
+import java.util.Random;
+
+/**
+ * Utility for generating random strings.
+ */
+public final class RandomStringUtils {
+
+    private static final String CHARS = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
+    private static final Random RANDOM = new SecureRandom();
+    private static final int HEX_MAX_INDEX = 16;
+    private static final int LOWER_ALPHANUMERIC_INDEX = 36;
+
+    // Utility class
+    private RandomStringUtils() {
+    }
+
+    /**
+     * Generate a string of the given length consisting of random characters within the range [0-9a-z].
+     *
+     * @param length The length of the random string to generate
+     * @return The random string
+     */
+    public static String generate(int length) {
+        return generate(length, LOWER_ALPHANUMERIC_INDEX);
+    }
+
+    /**
+     * Generate a random hexadecimal string of the given length. In other words, the generated string
+     * contains characters only within the range [0-9a-f].
+     *
+     * @param length The length of the random string to generate
+     * @return The random hexadecimal string
+     */
+    public static String generateHex(int length) {
+        return generate(length, HEX_MAX_INDEX);
+    }
+
+    /**
+     * Generate a random string with digits and lowercase and uppercase letters. The result of this
+     * method matches the pattern [0-9a-zA-Z].
+     *
+     * @param length The length of the random string to generate
+     * @return The random string
+     */
+    public static String generateLowerUpper(int length) {
+        return generate(length, CHARS.length());
+    }
+
+    private static String generate(int length, int maxIndex) {
+        if (length < 0) {
+            throw new IllegalArgumentException("Length must be positive but was " + length);
+        }
+        StringBuilder sb = new StringBuilder(length);
+        for (int i = 0; i < length; ++i) {
+            sb.append(CHARS.charAt(RANDOM.nextInt(maxIndex)));
+        }
+        return sb.toString();
+    }
+
+}