Static Field Write from Instance Method

ID

java.static_from_instance

Severity

low

Remediation Complexity

trivial

Remediation Risk

low

Remediation Effort

low

Resource

Reliability

Language

Java

Tags

CWE:366, concurrency, reliability

Description

Reports assignments in instance (non-static) methods that write to a static field. Writing to shared static state from an instance method is a common source of concurrency bugs.

Rationale

Static fields are shared across all instances of a class. When an instance method writes to a static field, multiple threads invoking the method on different instances can race on the same field without synchronization.

public class Counter {
    private static int count = 0;

    // Bad -- instance method modifies static state
    public void increment() {
        count++;
    }
}

Remediation

Use a synchronized block, an AtomicInteger, or move the method to a static context with proper synchronization.

public class Counter {
    private static final AtomicInteger count = new AtomicInteger(0);

    public void increment() {
        count.incrementAndGet();
    }
}

References