KEYCLOAK-19430 Revert deletion of RandomString

common/src/main/java/org/keycloak/common/util/RandomString.java

@@ -0,0 +1,70 @@
+package org.keycloak.common.util;
+
+import java.security.SecureRandom;
+import java.util.Locale;
+import java.util.Objects;
+import java.util.Random;
+
+/**
+ * @deprecated Replaced by {@link SecretGenerator}
+ */
+@Deprecated
+public class RandomString {
+
+    /**
+     * Generate a random string.
+     */
+    public String nextString() {
+        for (int idx = 0; idx < buf.length; ++idx)
+            buf[idx] = symbols[random.nextInt(symbols.length)];
+        return new String(buf);
+    }
+
+    public static final String upper = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
+
+    public static final String lower = upper.toLowerCase(Locale.ROOT);
+
+    public static final String digits = "0123456789";
+
+    public static final String alphanum = upper + lower + digits;
+
+    private final Random random;
+
+    private final char[] symbols;
+
+    private final char[] buf;
+
+    public RandomString(int length, Random random, String symbols) {
+        if (length < 1) throw new IllegalArgumentException();
+        if (symbols.length() < 2) throw new IllegalArgumentException();
+        this.random = Objects.requireNonNull(random);
+        this.symbols = symbols.toCharArray();
+        this.buf = new char[length];
+    }
+
+    /**
+     * Create an alphanumeric string generator.
+     */
+    public RandomString(int length, Random random) {
+        this(length, random, alphanum);
+    }
+
+    /**
+     * Create an alphanumeric strings from a secure generator.
+     */
+    public RandomString(int length) {
+        this(length, new SecureRandom());
+    }
+
+    /**
+     * Create session identifiers.
+     */
+    public RandomString() {
+        this(21);
+    }
+
+    public static String randomCode(int length) {
+        return new RandomString(length).nextString();
+    }
+
+}