PutDuringRemoveEldestEntryTest.java

gistfile1.txt

import java.util.LinkedHashMap;
import java.util.Map;
import junit.framework.TestCase;

public class PutDuringRemoveEldestEntryTest extends TestCase {
  public void test() {
    Map<String, String> map = new LinkedHashMap<String, String>(4) {
      @Override protected boolean removeEldestEntry(Map.Entry<String, String> eldest) {
        if (size() == 4) {
          super.put("a", "a"); // This will trigger doubleCapacity().
        }
        return false;
      }
    };
    map.put("c", "c");
    map.put("d", "d");
    map.put("e", "e");

    // This key has a different hash bucket on a 4-element vs. a 8-element table. But we'll select
    // the hash bucket before we resize the table, causing it to be stored in the wrong bucket.
    map.put("b", "b");

    assertEquals("c", map.get("c"));
    assertEquals("d", map.get("d"));
    assertEquals("e", map.get("e"));
    assertEquals("a", map.get("a"));
    assertEquals("b", map.get("b")); // Returns null because the hash bucket is wrong.
  }
}