DefensiveNullIntolerance.java

public final class Person {
  
  // Publicly accessible, all parameters validated.
  public static Person with(String name, int age, String favouriteColour) {
    checkArgument(age > 0, "age must be greater than 0");
    
    return new Person(
      checkNotNull(name, "name must not be null"),
      age,
      checkNotNull(favouriteColour, "favouriteColour must not be null")
    );
  )
   
  private final String name;
  private final int age;
  private final String favouriteColour;
  
  // Private, does nothing but assign parameters to fields
  private Person(String name, int age, String favouriteColour) {
    this.name = name;
    this.age = age;
    this.favouriteColour = favouriteColour;
  }
}