Hardcoded File Separator

ID

java.hardcoded_file_separator

Severity

low

Remediation Complexity

trivial

Remediation Risk

low

Remediation Effort

low

Resource

Reliability

Language

Java

Tags

best-practice, reliability

Description

Reports string literals containing hardcoded file path separators ("/" or "\\") used in string concatenation expressions that build file paths. Hardcoded separators break portability across operating systems.

Rationale

Different operating systems use different file path separators: Unix/macOS use /, Windows uses \. Hardcoding a separator makes the code non-portable:

File f = new File(dir + "/" + name);   // Fails on Windows
File f = new File(dir + "\\" + name);  // Fails on Unix

Remediation

Use java.io.File.separator, the two-argument File constructor, or java.nio.file.Path:

// Option 1: File.separator
File f = new File(dir + File.separator + name);

// Option 2: Two-argument constructor (preferred)
File f = new File(dir, name);

// Option 3: Path API
Path p = Path.of(dir, name);

References