Do Not Call Abstract Methods in Constructors

ID

java.no_abstract_call_in_constructor

Severity

high

Remediation Complexity

trivial

Remediation Risk

low

Remediation Effort

low

Resource

Reliability

Language

Java

Tags

CWE:668, reliability

Description

Reports calls to abstract methods inside constructors.

Rationale

When a constructor invokes an abstract (or overridable) method, the subclass’s override executes before the subclass constructor has finished initializing its fields. This means the overridden method may see null or default values for fields that the subclass constructor has not yet assigned, leading to subtle and hard-to-diagnose bugs.

// Bad — setup() runs before SubClass fields are initialized
abstract class Base {
    Base() {
        setup();
    }
    abstract void setup();
}

class SubClass extends Base {
    private String name = "default";
    void setup() {
        // name is still null here!
        System.out.println(name.length());
    }
}

Remediation

Avoid calling overridable methods from constructors. Use an explicit initialization method that callers invoke after construction, or use the Template Method pattern with final helper methods:

// Good — defer initialization
abstract class Base {
    Base() {
        // no abstract calls
    }
    abstract void setup();
}

// Caller creates and then initializes
Base b = new SubClass();
b.setup();

References