Double-checked locking

Reports double-checked locking.

Double-checked locking tries to initialize a field on demand and in a thread-safe manner, while avoiding the cost of synchronization. Unfortunately it is not thread-safe when used on a field that is not declared volatile. When using Java 1.4 or earlier, double-checked locking doesn't work even with a volatile field. Read the article linked above for a detailed explanation of the problem.

Example:

class Foo {
    private Helper helper = null

    Helper getHelper() {
        if (helper == null)
            synchronized(this) {
                if (helper == null) {
                    helper = new Helper()
                }
            }
        }
        return helper;
    }
}

Inspection options

Option	Type	Default
Ignore double-checked locking on volatile fields	Checkbox	false

Inspection Details
Available in:	IntelliJ IDEA 2023.3, Qodana for JVM 2023.3
Plugin:	Groovy, 233.SNAPSHOT

Last modified: 13 July 2023