NameListFailing.java

package example7;

import java.util.Collections;
import java.util.LinkedList;
import java.util.List;

public class NameListFailing {
	
	private List names = Collections.synchronizedList(new LinkedList());

	public void add(String name) {
		names.add(name);
	}

	//This code can break if we run the program multiple times
	//Even collection.syncronize also can fail when dealing with multiple threads if we don't code properly.
	//There's a solution here: don't rely on Collections.synchronizedList(). Instead, synchronize the code yourself:
	public String removeFirst() {
		if (names.size() > 0)
			return (String) names.remove(0);
		else
			return null;
	}

	public static void main(String[] args) {
		final NameListFailing nl = new NameListFailing();
		nl.add("Ozymandias");
		class NameDropper extends Thread {
			public void run() {
				String name = nl.removeFirst();
				System.out.println(name);
			}
		}
		Thread t1 = new NameDropper();
		Thread t2 = new NameDropper();
		t1.start();
		t2.start();
	}
}

SyncTest.java

package example7;

public class SyncTest {
	
	public void doStuff() {
		System.out.println("not synchronized");
		synchronized (this) {
			System.out.println("synchronized");
		}
	}

	public synchronized void doStuff1() {
		System.out.println("synchronized");
	}

	//  doStuff1 is equivalent to this:
	public void doStuff3() {
		synchronized (this) {
			System.out.println("synchronized");
		}
	}
	
	public static void getCount() {
		synchronized (SyncTest.class) {
			System.out.println("synchronized static method");
		}
	}
	
		public static void classMethod() throws ClassNotFoundException {
			Class cl = Class.forName("SyncTest");
			synchronized (cl) {
				// do stuff
			}
		}

}

Thing.java

package example7;

public class Thing {

	private static int staticField;
	private int nonstaticField;

	public static synchronized int getStaticField() {
		return staticField;
	}

	public static synchronized void setStaticField(int staticField) {
		Thing.staticField = staticField;
	}

	public synchronized int getNonstaticField() {
		return nonstaticField;
	}

	public synchronized void setNonstaticField(int nonstaticField) {
		this.nonstaticField = nonstaticField;
	}
}