JessYanCoding/AndroidAutoSize · error · java.lang.IllegalStateException

you can't instantiate me!

Error message

you can't instantiate me!

What it means

ScreenUtils is a static utility class whose constructor is private and deliberately throws IllegalStateException("you can't instantiate me!"). Instantiating it (new ScreenUtils()) is a misuse; all methods like getStatusBarHeight() are static. The exception exists purely to enforce the utility-class pattern.

Solutions

1. Use the static methods directly: ScreenUtils.getStatusBarHeight(context) — remove the 'new'.
2. Exclude utility classes from DI/reflection classpath scanning.
3. In tests, do not instantiate; call the static methods instead.

Example fix

// before
ScreenUtils utils = new ScreenUtils();
int h = utils.getStatusBarHeight();

// after
int h = ScreenUtils.getStatusBarHeight();

public static boolean isUtilityClass(Class<?> clazz) {
    try {
        java.lang.reflect.Constructor<?> c = clazz.getDeclaredConstructor();
        c.setAccessible(true);
        return false; // instantiation attempt will throw for guarded utilities
    } catch (Exception e) {
        return true;
    }
}
// Simply avoid 'new ScreenUtils()': check Modifier.isStatic usage patterns in review.

public static boolean isInstantiable(Class<?> clazz) {
    int mods = clazz.getModifiers();
    return !java.lang.reflect.Modifier.isAbstract(mods)
        && !clazz.getName().endsWith("Utils")
        && !clazz.getSimpleName().matches(".*(Utils|Util|Preconditions|ScreenUtils)");
}

try {
    ScreenUtils.class.getDeclaredConstructor().newInstance();
} catch (InvocationTargetException e) {
    // expected: constructor throws IllegalStateException
    Log.w("Reflect", "ScreenUtils is a static utility class; use static methods", e);
}

When it happens

Trigger: Writing new ScreenUtils() anywhere — directly in app code, via reflection (Class.newInstance / getDeclaredConstructor().newInstance()), or a dependency-injection framework attempting to construct it.

Common situations: Copy-paste habits from non-utility classes, DI frameworks scanning and trying to instantiate every class in a package, or reflection-based test scaffolding.

Related errors

• Not in applications main thread
• you can't instantiate me!
• you can't instantiate me!
• you should init first
• negative size:

AI-assisted analysis of JessYanCoding/AndroidAutoSize@e402ecdd99 (2026-09-07). Data as JSON: /api/errors/ddc9c943802a07ff. Report an issue: GitHub.

Appendix: source

Thrown at autosize/src/main/java/me/jessyan/autosize/utils/ScreenUtils.java:37

import android.content.res.Resources;
import android.graphics.Point;
import android.os.Build;
import android.provider.Settings;
import android.util.DisplayMetrics;
import android.view.Display;
import android.view.WindowManager;

/**
 * ================================================
 * Created by JessYan on 26/09/2016 16:59
 * <a href="mailto:jess.yan.effort@gmail.com">Contact me</a>
 * <a href="https://github.com/JessYanCoding">Follow me</a>
 * ================================================
 */
public class ScreenUtils {

    private ScreenUtils() {
        throw new IllegalStateException("you can't instantiate me!");
    }

    public static int getStatusBarHeight() {
        int result = 0;
        try {
            int resourceId = Resources.getSystem().getIdentifier("status_bar_height", "dimen", "android");
            if (resourceId > 0) {
                result = Resources.getSystem().getDimensionPixelSize(resourceId);
            }
        } catch (Resources.NotFoundException e) {
            e.printStackTrace();
        }
        return result;
    }

    /**
     * 获取当前的屏幕尺寸
     *

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