hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/util/TestStringInterner.java

/**
 * 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.hadoop.util;

import static org.junit.Assert.*;
import static org.apache.hadoop.util.StringInterner.*;

import org.junit.Test;

/**
 * 
 * Tests string interning {@link StringInterner}
 */
public class TestStringInterner {

  /**
   * Test different references are returned for any of string 
   * instances that are equal to each other but not interned.
   */
  @Test
  public void testNoIntern() {
    String literalABC = "ABC";
    String substringABC = "ABCDE".substring(0,3);
    String heapABC = new String("ABC");
    assertNotSame(literalABC, substringABC);
    assertNotSame(literalABC, heapABC);
    assertNotSame(substringABC, heapABC);
  }
  
  
  /**
   * Test the same strong reference is returned for any 
   * of string instances that are equal to each other.
   */
  @Test
  public void testStrongIntern() {
    String strongInternLiteralABC = strongIntern("ABC");
    String strongInternSubstringABC = strongIntern("ABCDE".substring(0,3));
    String strongInternHeapABC = strongIntern(new String("ABC"));
    assertSame(strongInternLiteralABC, strongInternSubstringABC);
    assertSame(strongInternLiteralABC, strongInternHeapABC);
    assertSame(strongInternSubstringABC, strongInternHeapABC);
  }
  
  
  /**
   * Test the same weak reference is returned for any 
   * of string instances that are equal to each other.
   */
  @Test
  public void testWeakIntern() {
    String weakInternLiteralABC = weakIntern("ABC");
    String weakInternSubstringABC = weakIntern("ABCDE".substring(0,3));
    String weakInternHeapABC = weakIntern(new String("ABC"));
    assertSame(weakInternLiteralABC, weakInternSubstringABC);
    assertSame(weakInternLiteralABC, weakInternHeapABC);
    assertSame(weakInternSubstringABC, weakInternHeapABC);
  }

}