Java example source code file (AbstractIteratorTest.java)

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Java - Java tags/keywords

abstractiterator, abstractiteratortest, gwtincompatible, illegalstateexception, integer, nosuchelementexception, object, override, runtimeexception, should, somecheckedexception, someuncheckedexception, suppresswarnings, testcase, util

The AbstractIteratorTest.java Java example source code

/*
 * Copyright (C) 2007 The Guava Authors
 *
 * Licensed 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 com.google.common.collect;

import com.google.common.annotations.GwtCompatible;
import com.google.common.annotations.GwtIncompatible;
import com.google.common.testing.GcFinalization;

import junit.framework.TestCase;

import java.lang.ref.WeakReference;
import java.util.Iterator;
import java.util.NoSuchElementException;

/**
 * Unit test for {@code AbstractIterator}.
 *
 * @author Kevin Bourrillion
 */
@SuppressWarnings("serial") // No serialization is used in this test
@GwtCompatible(emulated = true)
// TODO(cpovirk): why is this slow (>1m/test) under GWT when fully optimized?
public class AbstractIteratorTest extends TestCase {

  public void testDefaultBehaviorOfNextAndHasNext() {

    // This sample AbstractIterator returns 0 on the first call, 1 on the
    // second, then signals that it's reached the end of the data
    Iterator<Integer> iter = new AbstractIterator() {
      private int rep;
      @Override public Integer computeNext() {
        switch (rep++) {
          case 0:
            return 0;
          case 1:
            return 1;
          case 2:
            return endOfData();
          default:
            fail("Should not have been invoked again");
            return null;
        }
      }
    };

    assertTrue(iter.hasNext());
    assertEquals(0, (int) iter.next());

    // verify idempotence of hasNext()
    assertTrue(iter.hasNext());
    assertTrue(iter.hasNext());
    assertTrue(iter.hasNext());
    assertEquals(1, (int) iter.next());

    assertFalse(iter.hasNext());

    // Make sure computeNext() doesn't get invoked again
    assertFalse(iter.hasNext());

    try {
      iter.next();
      fail("no exception thrown");
    } catch (NoSuchElementException expected) {
    }
  }

  public void testDefaultBehaviorOfPeek() {
    /*
     * This sample AbstractIterator returns 0 on the first call, 1 on the
     * second, then signals that it's reached the end of the data
     */
    AbstractIterator<Integer> iter = new AbstractIterator() {
      private int rep;
      @Override public Integer computeNext() {
        switch (rep++) {
          case 0:
            return 0;
          case 1:
            return 1;
          case 2:
            return endOfData();
          default:
            fail("Should not have been invoked again");
            return null;
        }
      }
    };

    assertEquals(0, (int) iter.peek());
    assertEquals(0, (int) iter.peek());
    assertTrue(iter.hasNext());
    assertEquals(0, (int) iter.peek());
    assertEquals(0, (int) iter.next());

    assertEquals(1, (int) iter.peek());
    assertEquals(1, (int) iter.next());

    try {
      iter.peek();
      fail("peek() should throw NoSuchElementException at end");
    } catch (NoSuchElementException expected) {
    }

    try {
      iter.peek();
      fail("peek() should continue to throw NoSuchElementException at end");
    } catch (NoSuchElementException expected) {
    }

    try {
      iter.next();
      fail("next() should throw NoSuchElementException as usual");
    } catch (NoSuchElementException expected) {
    }

    try {
      iter.peek();
      fail("peek() should still throw NoSuchElementException after next()");
    } catch (NoSuchElementException expected) {
    }
  }

  @GwtIncompatible // weak references
  public void testFreesNextReference() {
    Iterator<Object> itr = new AbstractIterator