What causes "u can't instantiate me..." in Blankj/AndroidUtilCode?

Call static methods directly (e.g., CleanUtils.cleanInternalCache()) and never instantiate.

Blankj/AndroidUtilCode · info · UnsupportedOperationException

u can't instantiate me...

Error message

u can't instantiate me...

What it means

CleanUtils is a final utility class with only static cleanup helpers; its private constructor throws UnsupportedOperationException('u can't instantiate me...') to forbid construction. The throw is an intentional guard reachable only via reflection, since the class is final and the constructor is private.

Source

Thrown at lib/utilcode/src/main/java/com/blankj/utilcode/util/CleanUtils.java:23

import android.os.Build;
import android.os.Environment;

import java.io.File;

import androidx.annotation.RequiresApi;

/**
 * <pre>
 *     author: Blankj
 *     blog  : http://blankj.com
 *     time  : 2016/09/27
 *     desc  : utils about clean
 * </pre>
 */
public final class CleanUtils {

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

    /**
     * Clean the internal cache.
     * <p>directory: /data/data/package/cache</p>
     *
     * @return {@code true}: success<br>{@code false}: fail
     */
    public static boolean cleanInternalCache() {
        return UtilsBridge.deleteAllInDir(Utils.getApp().getCacheDir());
    }

    /**
     * Clean the internal files.
     * <p>directory: /data/data/package/files</p>
     *
     * @return {@code true}: success<br>{@code false}: fail
     */

View on GitHub (pinned to 7b4caf9e54)

Solutions

Call static methods directly (e.g., CleanUtils.cleanInternalCache()) and never instantiate.
Exclude the constructor from coverage requirements or use the coverage helper.
If testing the guard, assert UnsupportedOperationException is thrown rather than trying to succeed.
Remove reflective newInstance() calls against CleanUtils.class.

Defensive patterns

Strategy: validation

Validate before calling

// Never instantiate; call static methods directly.
boolean ok = CleanUtils.cleanInternalCache();

Try / catch

try {
    Constructor<CleanUtils> c = CleanUtils.class.getDeclaredConstructor();
    c.setAccessible(true);
    c.newInstance();
} catch (UnsupportedOperationException | InvocationTargetException e) {
    // expected: instantiation is forbidden by design
}

Prevention

Call CleanUtils static methods directly; never reflectively instantiate it.
Exclude private constructors from coverage tooling that auto-instantiates.
For guard tests, assert UnsupportedOperationException instead of trying to succeed.

When it happens

Trigger: Reflectively invoking the private constructor (setAccessible(true) + newInstance()); coverage or generic reflection tooling that instantiates every class; frameworks that auto-construct classes.

Common situations: Code-coverage tools (JaCoCo/Cobertura) covering private constructors; blanket reflection tests that instantiate all classes in a package; DI/serialization frameworks attempting no-arg construction.

Related errors

AI-assisted analysis of Blankj/AndroidUtilCode@7b4caf9e54 (2026-08-14). Data as JSON: /api/errors/9f58f45a71f5bee8. Report an issue: GitHub.