add user lookup command

src/main/java/cc/fascinated/bat/common/LongUtils.java

@@ -0,0 +1,21 @@
+package cc.fascinated.bat.common;
+
+/**
+ * @author Fascinated (fascinated7)
+ */
+public class LongUtils {
+    /**
+     * Checks if a string is a long
+     *
+     * @param string the string to check
+     * @return if the string is a long
+     */
+    public static boolean isLong(String string) {
+        try {
+            Long.parseLong(string);
+            return true;
+        } catch (NumberFormatException exception) {
+            return false;
+        }
+    }
+}