One Public Top-Level Type per File
ID |
java.one_public_class_per_file |
Severity |
info |
Remediation Complexity |
medium |
Remediation Risk |
low |
Remediation Effort |
medium |
Resource |
Code Smell |
Language |
Java |
Tags |
best-practice, code-style |
Description
Reports the second and subsequent public top-level type declarations in a single source file. The Java Language Specification requires that a source file contain at most one public top-level class, interface, or enum, and that its name match the file name.
Rationale
Placing multiple public types in one file breaks the standard one-to-one mapping between file names and public types. This makes classes harder to locate, confuses build tools that rely on the convention, and violates the JLS rule that will cause compilation errors in most environments.
// File: Foo.java
public class Foo { } // OK
public class Bar { } // Violation — second public typeRemediation
Move each public type into its own source file named after the type.
// File: Foo.java
public class Foo { }
// File: Bar.java (separate file)
public class Bar { }