7.14 Object Creation Process

1. Code

public class Test
{
    private Integer val = 10;

    public static void main(String[] args)
    {
        Test test  = new Test();
    }
}

2. Bytecode

2.1. Explanation

It can be seen that Test test = new Test(); is divided into three steps:

1. Create a Test instance.
2. Assign a value to the val property of the Test instance.
3. Assign the reference of the Test instance to the test variable.

After the first step is completed, the object is in a partially initialized state.

The issue is with steps 2 and 3. These two steps do not have a strong dependency, so according to CPU pipeline technology, these two instructions may be reordered, meaning the execution order may become 1-3-2.

2.2. Solution

Add the volatile modifier to the val variable to prohibit instruction reordering.