Blankj/AndroidUtilCode · error · UnsupportedOperationException

u can't instantiate me...

Error message

u can't instantiate me...

What it means

DebugUtils in the utildebug-no-op module is a no-op stub used in release builds to strip debug tooling at compile time. Its private constructor throws UnsupportedOperationException to prevent instantiation. All public methods (setIconId, addDebugs) are empty no-ops; the class exists only as a static API surface.

Source

Thrown at lib/utildebug-no-op/src/main/java/com/blankj/utildebug/DebugUtils.java:18

package com.blankj.utildebug;

import com.blankj.utildebug.debug.IDebug;

import java.util.List;

/**
 * <pre>
 *     author: blankj
 *     blog  : http://blankj.com
 *     time  : 2019/08/28
 *     desc  : utils about debug
 * </pre>
 */
public class DebugUtils {

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

    public static void setIconId(final int icon) {
    }

    public static void addDebugs(final List<IDebug> debugs) {
    }
}

View on GitHub (pinned to 7b4caf9e54)

Solutions

  1. Call the (no-op) static methods: DebugUtils.setIconId(res) instead of constructing.
  2. Provide a Gson InstanceCreator / Jackson mixin returning a sentinel so the constructor is not invoked.
  3. Use Mockito.mockStatic for mocking rather than constructing DebugUtils.
  4. Keep the class constructor private; remember this flavor intentionally has empty bodies.

Example fix

// before
DebugUtils du = new DebugUtils();

// after
DebugUtils.setIconId(R.drawable.ic_debug);
Defensive patterns

Strategy: validation

Validate before calling

if (Modifier.isFinal(DebugUtils.class.getModifiers())) {
  throw new IllegalStateException("DebugUtils (no-op) is static-only.");
}

Prevention

When it happens

Trigger: Reflective instantiation via DebugUtils.class.getDeclaredConstructor().setAccessible(true).newInstance(), or transitively through Gson/Jackson deserialization, Mockito/PowerMock, Kotlin reflection, or a DI scan in a release-flavor build that resolves the no-op variant.

Common situations: Release builds swapping in the no-op artifact; serialization frameworks binding a field to DebugUtils; mock frameworks; coverage tooling; accidental construction after weakening modifiers.

Related errors

AI-assisted analysis of Blankj/AndroidUtilCode@7b4caf9e54 (2026-08-14). Data as JSON: /api/errors/7165150840b66816. Report an issue: GitHub.