# Hide Default Constructor In Utility Classes

Properties
Description
Benefits
Code Changes
Tags

# Properties

Property	Value
Rule ID	HideDefaultConstructorInUtilityClasses
First seen in jSparrow version	3.11.0
Minimum Java version	1.1
Remediation cost	5 min
Links	S1118

# Description

Utility classes are classes containing static properties only. Those classes should not be instantiated. A private constructor, which throws an IllegalStateException, is introduced to utility classes by this rule, if the following criteria are met:

Only static methods and fields are present
No constructor is declared
No main method is defined
The default constructor isn't invoked anywhere in the current workspace

This hides the default public constructor and thus prevents the instantiation of such a class.

# Benefits

Prevents the bad practice of unnecessary instatiation of utility classes.

# Code Changes

Pre

    public class UtilityClass {
        public static doSomething() {
            ...
            System.out.println("did something");
        }

        public static doSomethingElse() {
            ...
            System.out.println("did something else");
        }
    }

Post

    public class UtilityClass {
        private UtilityClass() {
            throw new IllegalStateException("Utility class");
        }

        public static doSomething() {
            ...
            System.out.println("did something");
        }

        public static doSomethingElse() {
            ...
            System.out.println("did something else");
        }
    }

Automatic Application of This Rule

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

jSparrow Pro version