java变量本身是线程安全的吗?更新变量时?

Suppose I have two threads updating an object, and one thread reading from that object with no synchronization. Obviously, this is run condition. However, I am wondering if the variable itself can only partially written.

public class CommonObject extends Object
{
    static int memberVar=-1;
}

public class Input1Thread extends Thread
{   
    public void run()   
    {
        while(true)
            CommonObject.memberVar = 1
    }
}

public class Input2Thread extends Thread
{   
    public void run()   
    {
        while(true)
            CommonObject.memberVar = 2;
    }
}

public class OutputThread extends Thread
{   
    public void run()   
    {
        while(true)
            System.out.println("CommonObject.memberVar"+ CommonObject.memberVar);
    }
}  

我会假设打印出来的值也是 2 或 1.但是，我想知道变量是否有可能被设置到一半?