What is synchronized on Java?

1. Why is used? 

synchronized is lock for avoding race condition.

2. How do?

1) function

ex) 

public synchronized void setData(int data) {...}

2) block

ex) 

public void setData(int data) {

    synchronized(this) {

        m_data = data;

    }

}

3) value

ex)

private int m_data;

public void setData(int data) {

    synchronized(m_data) {

        m_data = data;

    }

}

from: http://blog.naver.com/meelong0/140094191195