didi/DoKit · error · IllegalArgumentException

Max size must be positive.

Error message

Max size must be positive.

What it means

LruCache's constructor throws IllegalArgumentException when maxSize is <= 0. The cache needs a positive byte budget to evict against; a zero or negative budget is a configuration mistake. Fail-fast guard, consistent with android.util.LruCache.

Source

Thrown at Android/dokit/src/main/java/com/didichuxing/doraemonkit/picasso/LruCache.java:43

public class LruCache implements Cache {
  final LinkedHashMap<String, Bitmap> map;
  private final int maxSize;

  private int size;
  private int putCount;
  private int evictionCount;
  private int hitCount;
  private int missCount;

  /** Create a cache using an appropriate portion of the available RAM as the maximum size. */
  public LruCache(Context context) {
    this(Utils.calculateMemoryCacheSize(context));
  }

  /** Create a cache with a given maximum size in bytes. */
  public LruCache(int maxSize) {
    if (maxSize <= 0) {
      throw new IllegalArgumentException("Max size must be positive.");
    }
    this.maxSize = maxSize;
    this.map = new LinkedHashMap<String, Bitmap>(0, 0.75f, true);
  }

  @Override public Bitmap get(String key) {
    if (key == null) {
      throw new NullPointerException("key == null");
    }

    Bitmap mapValue;
    synchronized (this) {
      mapValue = map.get(key);
      if (mapValue != null) {
        hitCount++;
        return mapValue;
      }
      missCount++;

View on GitHub (pinned to 626827cddb)

Solutions

1. Clamp the computed size to a sensible positive minimum before constructing: Math.max(size, 256 * 1024)
2. Use the LruCache(Context) constructor, which sizes the cache from available RAM automatically
3. Check the size-computation math for truncation or overflow

Example fix

// before
int size = (int) (Runtime.getRuntime().maxMemory() / 10f * 0); // oops -> 0
new LruCache(size); // IllegalArgumentException

// after
int size = Math.max((int) (Runtime.getRuntime().maxMemory() / 10), 1024 * 1024);
new LruCache(size);

int size = Math.max(computeCacheBytes(context), 1024 * 1024);
new LruCache(size); // or simply new LruCache(context)

boolean isValidCacheSize(int maxSize) { return maxSize > 0; }

When it happens

Trigger: Constructing new LruCache(0) or new LruCache(negative), e.g. computing a percentage of free memory that rounded/truncated to zero.

Common situations: Cache size computed from device metrics (free RAM, heap percentage) that yields 0 on constrained devices or emulators; hardcoded 0 during testing; integer overflow when computing a large size that wraps negative.

Related errors

• uri == null
• path == null
• file == null
• Path must not be empty.
• Resource ID must not be zero.

AI-assisted analysis of didi/DoKit@626827cddb (2026-08-14). Data as JSON: /api/errors/cde26f8a546417bf. Report an issue: GitHub.