Uninitialized Field Read in Constructor

ID

java.uninit_read_constructor

Severity

low

Remediation Complexity

trivial

Remediation Risk

low

Remediation Effort

low

Resource

Reliability

Language

Java

Tags

reliability

Description

Reports fields that are read in a constructor before being assigned a value. Reading an uninitialized field yields the type’s default value (null, 0, false), which is almost always unintended.

Rationale

When a constructor reads a field before assigning it, the field still holds its default value. This is often a bug where the developer intended to use the constructor parameter or assumed the field was already initialized.

public class Config {
    private String name;

    public Config(String n) {
        System.out.println(name); // Bug: reads null
        name = n;
    }
}

Remediation

Assign the field before reading it, or reorder the constructor statements.

public Config(String n) {
    name = n;
    System.out.println(name); // Now prints the assigned value
}

References