jSparrow Documentation

# Make Fields And Variables Final

# Properties

Property Value
Rule ID MakeFieldsAndVariablesFinal
First seen in jSparrow version 3.12.0
Minimum Java version 1.1
Remediation cost 5 min

# Description

This rule declares private fields and local variables final, if they are effectively final.

The criteria for being effectively final are as follows:

  • The variable or field is not assigned after its initialisation
  • Initialisation of non-static fields:
    • At the declaration OR
    • In a non-static class initialiser OR
    • In ALL constructors of the class
  • Initialisation of static fields:
    • At the declaration OR
    • In a static initialiser

# Benefits

Readability and maintainability of code is improved and accidental reassignments are prevented for affected fields and variables.

# Requirement & Tags

Requirements

Java 1.1

Tags

# Code Changes

# Assignments

Pre

public class MakeFinal {
    private String nonStaticField = "nonStaticField";
    private String nonStaticFieldEffectivelyFinal ="nonStaticFieldEffectivelyFinal";
    private static String staticField = "staticField";
    private static String staticFieldEffectivelyFinal = "staticFieldEffectivelyFinal";

    public void localVariables() {
        int i = 0;
        int j = 0;
        System.out.println(i);
        System.out.println(j++);
    }

    public void nonStaticFields() {
        nonStaticField += "Altered";
        System.out.println(nonStaticField);
        System.out.println(nonStaticFieldEffectivelyFinal);
    }

    public static void staticFields() {
        staticField = staticField + "Altered";
        System.out.println(staticField);
        System.out.println(staticFieldEffectivelyFinal);
    }
}

Post

public class MakeFinal {
    private String nonStaticField ="nonStaticField";
    private final String nonStaticFieldEffectivelyFinal ="nonStaticFieldEffectivelyFinal";
    private static String staticField = "staticField";
    private static final String staticFieldEffectivelyFinal = "staticFieldEffectivelyFinal";

    public void localVariables() {
        final int i = 0;
        int j = 0;
        System.out.println(i);
        System.out.println(j++);
    }

    public void nonStaticFields() {
        nonStaticField += "Altered";
        System.out.println(nonStaticField);
        System.out.println(nonStaticFieldEffectivelyFinal);
    }

    public static void staticFields() {
        staticField = staticField + "Altered";
        System.out.println(staticField);
        System.out.println(staticFieldEffectivelyFinal);
    }
}

# static Field Initialisation

Pre

public class MakeFinal {
    private static String initInDeclaration = "initInDeclaration";
    private static String initInStaticInitialiser;
    private static String initInDeclarationAndStaticInitialiser = "initInDeclarationAndStaticInitialiser";
    private static String noInit;

    static {
        initInStaticInitialiser = "initInStaticInitialiser";
        initInDeclarationAndStaticInitialiser = "initInDeclarationAndStaticInitialiser";
    }

    ...
}

Post

public class MakeFinal {
    private static final String initInDeclaration = "initInDeclaration";
    private static final String initInStaticInitialiser;
    private static String initInDeclarationAndStaticInitialiser = "initInDeclarationAndStaticInitialiser";
    private static String noInit;

    static {
        initInStaticInitialiser = "initInStaticInitialiser";
        initInDeclarationAndStaticInitialiser = "initInDeclarationAndStaticInitialiser";
    }

    ...
}

# Non-static Field Initialisation

Pre

public class MakeFinal {
    private String initInDeclaration = "initInDeclaration";
    private String initInClassInitialiser;
    private String initInAllConstructors;
    private String initInOneConstructorOnly;
    private String initInDeclarationAndClassInitialiser = "initInDeclarationAndClassInitialiser";
    private String noInit;

    {
        initInClassInitialiser = "initInClassInitialiser";
        initInDeclarationAndClassInitialiser = "initInDeclarationAndClassInitialiser";
    }

    public MakeFinal()  {
        initInAllConstructors = "initInAllConstructors";
        initInOneConstructorOnly = "initInOneConstructorOnly";
    }

    public MakeFinal(String arg1) {
        initInAllConstructors = "initInAllConstructors";
    }

    ...
}

Post

public class MakeFinal {
    private final String initInDeclaration = "initInDeclaration";
    private final String initInClassInitialiser;
    private final String initInAllConstructors;
    private String initInOneConstructorOnly;
    private String initInDeclarationAndClassInitialiser = "initInDeclarationAndClassInitialiser";
    private String noInit;

    {
        initInClassInitialiser = "initInClassInitialiser";
        initInDeclarationAndClassInitialiser = "initInDeclarationAndClassInitialiser";
    }

    public MakeFinal()  {
        initInAllConstructors = "initInAllConstructors";
        initInOneConstructorOnly = "initInOneConstructorOnly";
    }

    public MakeFinal(String arg1) {
        initInAllConstructors = "initInAllConstructors";
    }

    ...
}

# Limitations

This rule only affects private fields and local variables at the moment. public, protected or package-private fields as well as method parameters are not considered yet.

← Make SerialVersionUID Static Final →