org.eclipse.jdt.ui.tests/leaks/org/eclipse/jdt/ui/leaktest/example/LeakTestExample.java

/*******************************************************************************
 * Copyright (c) 2000, 2020 IBM Corporation and others.
 *
 * This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License 2.0
 * which accompanies this distribution, and is available at
 * https://www.eclipse.org/legal/epl-2.0/
 *
 * SPDX-License-Identifier: EPL-2.0
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.jdt.ui.leaktest.example;

import java.util.ArrayList;

import org.junit.Rule;
import org.junit.Test;

import org.eclipse.jdt.ui.leaktest.LeakTestCase;
import org.eclipse.jdt.ui.tests.core.rules.LeakTestSetup;

public class LeakTestExample extends LeakTestCase {

	@Rule
	public LeakTestSetup projectSetup = new LeakTestSetup();

	private static class MyClass {
	}

	private Object fGlobalReference;

	private ArrayList<Object> fGlobalList= new ArrayList<>();

	@Test
	public void testLeakGlobalReference() throws Exception {
		fGlobalList.clear();

		Class<MyClass> cl= MyClass.class;

		// get the count before creating the instance
		int count1= getInstanceCount(cl);

		// create the instance
		fGlobalReference= new MyClass();

		// get the count after creating the instance
		int count2= getInstanceCount(cl);
		assertDifferentCount("after creation: ", count1, count2);

		// clear all references to the instance
		fGlobalReference= null;

		// get the count after clearing the reference of the instance
		int count3= getInstanceCount(cl);
		assertEqualCount("after clear: ", count1, count3);
	}

	@Test
	public void testNoLeakGlobalReference() throws Exception {
		fGlobalList.clear();
		Class<MyClass> cl= MyClass.class;

		// get the count before creating my instance
		int count1= getInstanceCount(cl);

		// create the instance
		fGlobalReference= new MyClass();

		// get the count after creating the instance
		int count2= getInstanceCount(cl);
		assertDifferentCount("after creation: ", count1, count2);

		// add the instance to a list
		fGlobalList.add(fGlobalReference);

		// clear the global references of the instance
		fGlobalReference= null;

		// get the count after clearing the global reference of the instance
		// instance should still be here, it is referenced in the list
		int count3= getInstanceCount(cl);
		assertEqualCount("after clear: ", count2, count3);
	}

}