Make Fields And Variables Final

• Properties
• Description
• Benefits
• Code Changes
  • Assignments
  • static Field Initialisation
  • Non-static Field Initialisation
• Limitations
• Tags

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.

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.

Automatic Application of This Rule

The automatic application of this rule is supported in the following jSparrow version:

• jSparrow Pro version

Tags

Tags

Java 1.1, Readability