Blankj/AndroidUtilCode · warning · UnsupportedOperationException

u can't instantiate me...

Error message

u can't instantiate me...

What it means

DangerousUtils is a utility class whose private constructor throws UnsupportedOperationException to block instantiation. All functionality is exposed as static methods; the class is not meant to hold instance state.

Source

Thrown at lib/subutil/src/main/java/com/blankj/subutil/util/DangerousUtils.java:37

import java.util.List;

import androidx.annotation.RequiresPermission;

import static android.Manifest.permission.MODIFY_PHONE_STATE;
import static android.Manifest.permission.SEND_SMS;

/**
 * <pre>
 *     author: Blankj
 *     blog  : http://blankj.com
 *     time  : 2019/06/29
 *     desc  :
 * </pre>
 */
public class DangerousUtils {

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

    ///////////////////////////////////////////////////////////////////////////
    // AppUtils
    ///////////////////////////////////////////////////////////////////////////

    /**
     * Install the app silently.
     * <p>Without root permission must hold
     * {@code android:sharedUserId="android.uid.shell"} and
     * {@code <uses-permission android:name="android.permission.INSTALL_PACKAGES" />}</p>
     *
     * @param filePath The path of file.
     * @return {@code true}: success<br>{@code false}: fail
     */
    public static boolean installAppSilent(final String filePath) {
        return installAppSilent(getFileByPath(filePath), null);
    }

View on GitHub (pinned to 7b4caf9e54)

Solutions

  1. Use the static methods directly, e.g. DangerousUtils.silentInstall(...); never hold an instance.
  2. Configure reflective frameworks to skip final utility classes.
  3. Remove reflection that constructs DangerousUtils.

Example fix

// before
DangerousUtils d = reflectiveNew(DangerousUtils.class); // throws

// after
DangerousUtils.installAppSilent(filePath, listener);
Defensive patterns

Strategy: validation

Validate before calling

// DangerousUtils is static-only; never instantiate.
DangerousUtils.installAppSilent(path, listener);

Type guard

private static boolean isStaticUtility(Class<?> c) {
    return Modifier.isFinal(c.getModifiers()) && hasOnlyStaticMethods(c);
}

Prevention

When it happens

Trigger: Reflective instantiation (Constructor.newInstance) or unsafe object creation targeting DangerousUtils.

Common situations: DI/serialization frameworks or code generators that instantiate arbitrary classes; reflective test scaffolding that builds utility classes.

Related errors

AI-assisted analysis of Blankj/AndroidUtilCode@7b4caf9e54 (2026-08-14). Data as JSON: /api/errors/51a66251eec14e79. Report an issue: GitHub.