ExplicitInitialization

Since Checkstyle 3.2

Description

Checks if any class or object member is explicitly initialized to default for its type value (null for object references, zero for numeric types and char and false for boolean.

Rationale: Each instance variable gets initialized twice, to the same value. Java initializes each instance variable to its default value (0 or null) before performing any initialization specified in the code. So there is a minor inefficiency.

Properties

name description type default value since
onlyObjectReferences Control whether only explicit initializations made to null for objects should be checked. boolean false 7.8

Examples

To configure the check: 

<module name="Checker">
  <module name="TreeWalker">
    <module name="ExplicitInitialization"/>
  </module>
</module>

Example:

public class Example1 {
  private int intField1 = 0; // violation
  private int intField2 = 1;
  private int intField3;

  private char charField1 = '\0'; // violation
  private char charField2 = 'b';
  private char charField3;

  private boolean boolField1 = false; // violation
  private boolean boolField2 = true;
  private boolean boolField3;

  private Object objField1 = null; // violation
  private Object objField2 = new Object();
  private Object objField3;

  private int arrField1[] = null; // violation
  private int arrField2[] = new int[10];
  private int arrField3[];
}

To configure the check so that it only checks for objects that explicitly initialize to null: 

<module name="Checker">
  <module name="TreeWalker">
    <module name="ExplicitInitialization">
      <property name="onlyObjectReferences" value="true"/>
    </module>
  </module>
</module>

Example:

public class Example2 {
  private int intField1 = 0; // ignored
  private int intField2 = 1;
  private int intField3;

  private char charField1 = '\0'; // ignored
  private char charField2 = 'b';
  private char charField3;

  private boolean boolField1 = false; // ignored
  private boolean boolField2 = true;
  private boolean boolField3;

  private Object objField1 = null; // violation
  private Object objField2 = new Object();
  private Object objField3;

  private int arrField1[] = null; // violation
  private int arrField2[] = new int[10];
  private int arrField3[];
}

Example of Usage

Violation Messages

All messages can be customized if the default message doesn't suit you. Please see the documentation to learn how to.

Package

com.puppycrawl.tools.checkstyle.checks.coding

Parent Module

TreeWalker