[GitHub] [accumulo] brianloss commented on a change in pull request #1925: Move String intern code and make it generic

[GitBox <gi...@apache.org>]

brianloss commented on a change in pull request #1925:
URL: https://github.com/apache/accumulo/pull/1925#discussion_r574474818



##########
File path: core/src/test/java/org/apache/accumulo/core/util/InternerTest.java
##########
@@ -0,0 +1,110 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+package org.apache.accumulo.core.util;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNotEquals;
+import static org.junit.Assert.assertNotSame;
+import static org.junit.Assert.assertSame;
+
+import org.junit.Test;
+
+public class InternerTest {
+
+  private class TestObj {
+    private final int id;
+
+    TestObj(int id) {
+      this.id = id;
+    }
+
+    @Override
+    public int hashCode() {
+      return id;
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+      if (obj instanceof TestObj) {
+        return ((TestObj) obj).id == this.id;
+      }
+      return false;
+    }
+  }
+
+  @Test
+  public void testInternDedupes() {
+    var interner = new Interner<TestObj>();
+
+    var obj1 = new TestObj(1);
+    var obj1_dupe = new TestObj(1);
+    assertSame(obj1, obj1);
+    assertNotSame(obj1, obj1_dupe);
+    assertEquals(obj1, obj1_dupe);
+    assertEquals(obj1.hashCode(), obj1_dupe.hashCode());
+
+    // verify object gets added to the intern pool
+    assertSame(obj1, interner.intern(obj1));
+    assertEquals(1, interner.size());
+
+    // verify equivalent, but not the same object, gets deduplicated
+    assertSame(obj1, interner.intern(obj1_dupe));
+    assertEquals(1, interner.size());
+
+    // verify second object grows the intern pool size
+    var obj2 = new TestObj(2);
+    assertNotSame(obj1, obj2);
+    assertNotEquals(obj1, obj2);
+    var intern2 = interner.intern(obj2);
+    assertEquals(2, interner.size());
+
+    // sanity check to ensure we got the same object back for obj2, and it's not mangled with obj1
+    assertSame(obj2, intern2);
+    assertNotEquals(obj1, intern2);
+  }
+
+  @Test(timeout = 10_000)
+  public void testInternsGetGarbageCollected() {
+    var interner = new Interner<TestObj>();
+    assertEquals(0, interner.size()); // ensure empty
+
+    // add one and keep a strong reference
+    var obj1 = interner.intern(new TestObj(1));
+    assertEquals(1, interner.size());
+
+    // try to add a second, weakly referenced object until it sticks (may be GC'd between checks)
+    do {
+      interner.intern(new TestObj(2));
+    } while (interner.size() != 2);
+
+    // best effort to GC until the weakly reachable object goes away or until test times out

Review comment:
       If you have to add the timeout, doesn't this mean the test is potentially flaky? Would it be better to have the test pass in the unlikely event that System.gc doesn't eventually cause garbage collection to occur?




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