String Equality Use Equals

ID

java.string_equality_use_equals

Severity

high

Remediation Complexity

trivial

Remediation Risk

low

Remediation Effort

low

Resource

Reliability

Language

Java

Tags

CWE:597, reliability, suspicious-comparison

Description

Reports uses of == or != to compare String objects. These operators test reference equality, not content equality, leading to subtle bugs.

Rationale

The == operator checks whether two references point to the same object in memory, not whether they contain the same characters. While string literals may be interned, strings created at runtime (from new String(), substring(), concatenation, I/O, etc.) are typically distinct objects:

String a = getInput();
String b = getInput();
if (a == b) {          // Bug: compares references, not content
    process();
}

Remediation

Use String.equals() or Objects.equals() for content comparison:

String a = getInput();
String b = getInput();
if (a.equals(b)) {     // Correct: compares content
    process();
}

Comparisons against null using == or != are valid and are not flagged by this rule.

References