diff --git a/plusone-basic/plusone-basic-common/src/main/java/xyz/zhouxy/plusone/util/RandomUtil.java b/plusone-basic/plusone-basic-common/src/main/java/xyz/zhouxy/plusone/util/RandomUtil.java
new file mode 100644
index 0000000..df9253d
--- /dev/null
+++ b/plusone-basic/plusone-basic-common/src/main/java/xyz/zhouxy/plusone/util/RandomUtil.java
@@ -0,0 +1,18 @@
+package xyz.zhouxy.plusone.util;
+
+import java.util.concurrent.ThreadLocalRandom;
+
+public final class RandomUtil {
+    private RandomUtil() {
+        throw new IllegalStateException("Utility class");
+    }
+
+    public static String randomStr(char[] sourceCharacters, int length) {
+        ThreadLocalRandom random = ThreadLocalRandom.current();
+        char[] result = new char[length];
+        for (int i = 0; i < length; i++) {
+            result[i] = sourceCharacters[random.nextInt(sourceCharacters.length)];
+        }
+        return String.valueOf(result);
+    }
+}
diff --git a/plusone-basic/plusone-basic-common/src/test/java/xyz/zhouxy/plusone/util/RandomUtilTests.java b/plusone-basic/plusone-basic-common/src/test/java/xyz/zhouxy/plusone/util/RandomUtilTests.java
new file mode 100644
index 0000000..ad3399b
--- /dev/null
+++ b/plusone-basic/plusone-basic-common/src/test/java/xyz/zhouxy/plusone/util/RandomUtilTests.java
@@ -0,0 +1,23 @@
+package xyz.zhouxy.plusone.util;
+
+import java.util.Arrays;
+
+import org.junit.jupiter.api.Test;
+
+import lombok.extern.slf4j.Slf4j;
+
+@Slf4j
+class RandomUtilTests {
+
+    @Test
+    void testRandom() {
+        String[] s = new String[20];
+        for (int i = 0; i < 20; i++) {
+            s[i] = RandomUtil.randomStr(
+                    "0123456789qwertyuiopasdfghjklzxcvbnmQWERTYUIOPASDFGHJKLZXCVBNM~`!@#$%^&*()_-+={[\\|/:;\"',.<>?]}"
+                            .toCharArray(),
+                    28);
+        }
+        log.info("{}", Arrays.toString(s));
+    }
+}