Item 2: synchronized用法

1. public synchronized void setName(String name);
2. synchronized(this);
3. synchronized(arrayList){arrayList.add(new someClass());}

 例如：

package testsynchronized;

class Student {
	private String name;

	private String id;

	public String getName() {
		return name;
	}

	public String getId() {
		return id;
	}

	public void setId(String id) {
		this.id = id;
	}

	public void setName(String name) {
		this.name = name;
	}
}

public class TestSynchronized {

	Student student = new Student();

	Integer number;

	TestSynchronized() {
		for (int i = 0; i < 100; i++) {
			new Thread(new Runnable() {
				public void run() {
					while (true) {
						setNameAndId();
					}
				}
			}).start();
		}
	}
	//去除掉synchronized关键字进行测试，发现多线程下会产生数据不同步
	synchronized void setNameAndId() {
		number = new Integer((int) (100 * Math.random()));
		student.setName(number.toString());
		student.setId(number.toString());
		if (!student.getName().equals(student.getId())) {
			System.out.println("The name of student: " + student.getName()
					+ " is not equal with his id " + student.getId());
		}
	}

	public static void main(String[] str) {
		new TestSynchronized();
		System.out.println("The main function has ended!");
	}
}