*This rule was deprecated for Java before it was implemented.*

> in Java the members are initialized to default values (i.e. zero and null), so the rule doesn’t bring much value.

https://discuss.sonarsource.com/t/is-the-rule-s2107-implemented-planned-duplicate-for-java/15217/2[discuss post]

== Why is this an issue?

Class members that are not assigned a default value and are not initialized in a constructor will be set to null by the compiler. Even if code exists to properly set those members, there is a risk that they will be dereferenced before it is called, resulting in a ``++NullPointerException++``. 


Because you cannot guarantee that such classes will always be used properly, class members should always be initialized.


This rule flags members which have no default value and which are left uninitialized by at least one class constructor, but which are unconditionally dereferenced somewhere in the code.


=== Noncompliant code example

[source,text]
----
public class Team {

  int limit = 30;
  List<Player> roster;  // Noncompliant; no default & not initialized by constructor
  Person coach;

  public Team (Person coach) { // roster is left uninitialized
    this.coach = coach;
  }

  public void add(Player p) {
    if (roster == null) {
      roster = new ArrayList<Player>();
    }
    roster.add(p);
  }

  public boolean isFull() {  // NPE if called before add()
    return roster.size() < limit;
  }
}
----


=== Compliant solution

[source,text]
----
public class Team {

  int limit = 30;
  List<Player> roster = new ArrayList<Player>();
  Person coach;

  public Team (Person coach) {
    this.coach = coach;
  }

  public void add(Player p) {
    roster.add(p);
  }

  // ...
----
or 

[source,text]
----
public class Team {

  int limit = 30;
  List<Player> roster;
  Person coach;

  public Team (Person coach) {
    this.coach = coach;
    this.roster = new ArrayList<Player>();
  }

  public void add(Player p) {
    roster.add(p);
  }

  // ...
----

