Blankj/AndroidUtilCode · error · UnsupportedOperationException

u can't instantiate me...

Error message

u can't instantiate me...

What it means

RegexUtils is a final utility class providing static methods for regex-based validation (isMobileSimple, isEmail, isURL, isIDCard15/18, etc.) with an internal SimpleArrayMap for city lookups. Its private constructor throws UnsupportedOperationException to enforce static-only access.

Source

Thrown at lib/utilcode/src/main/java/com/blankj/utilcode/util/RegexUtils.java:26

import java.util.Collections;
import java.util.List;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

/**
 * <pre>
 *     author: Blankj
 *     blog  : http://blankj.com
 *     time  : 2016/08/02
 *     desc  : utils about regex
 * </pre>
 */
public final class RegexUtils {

    private final static SimpleArrayMap<String, String> CITY_MAP = new SimpleArrayMap<>();

    private RegexUtils() {
        throw new UnsupportedOperationException("u can't instantiate me...");
    }

    ///////////////////////////////////////////////////////////////////////////
    // If u want more please visit http://toutiao.com/i6231678548520731137
    ///////////////////////////////////////////////////////////////////////////

    /**
     * Return whether input matches regex of simple mobile.
     *
     * @param input The input.
     * @return {@code true}: yes<br>{@code false}: no
     */
    public static boolean isMobileSimple(final CharSequence input) {
        return isMatch(RegexConstants.REGEX_MOBILE_SIMPLE, input);
    }

    
    /**

View on GitHub (pinned to 7b4caf9e54)

Solutions

  1. Use static methods: RegexUtils.isMobileExact(input), RegexUtils.isEmail(email). Never call new RegexUtils().
  2. Exclude utility classes from DI scanning and serialization configs.
  3. Mock static methods with mockito-inline for testing.

Example fix

// before
RegexUtils ru = new RegexUtils();
boolean valid = ru.isEmail("a@b.com");

// after
boolean valid = RegexUtils.isEmail("a@b.com");
Defensive patterns

Strategy: type-guard

Validate before calling

// RegexUtils is static-only
boolean validEmail = RegexUtils.isEmail("test@example.com");
boolean validPhone = RegexUtils.isMobileExact("13800138000");

Type guard

static boolean isStaticUtility(Class<?> c) {
    return Modifier.isFinal(c.getModifiers()) && c.getSimpleName().endsWith("Utils");
}

Try / catch

try {
    RegexUtils.class.getDeclaredConstructor().setAccessible(true);
    RegexUtils.class.getDeclaredConstructor().newInstance();
} catch (UnsupportedOperationException e) {
    // Use static methods
}

Prevention

When it happens

Trigger: Direct or reflective instantiation by DI frameworks, mocking libraries, serialization frameworks, or manual reflection.

Common situations: DI component scanning traverses the utility package; a test framework instantiates all classes for coverage; a serialization library targets the class.

Related errors

AI-assisted analysis of Blankj/AndroidUtilCode@7b4caf9e54 (2026-08-14). Data as JSON: /api/errors/9e13745eb9833ff2. Report an issue: GitHub.