forax / flexible-constructor

Examples of flexible constructors (JEP 447) and more recent JEPs

Flexible Constructors

Examples of flexible constructors (JEP 447) and the more recent JEP (Flexible constructors).

Can have statement before super(...)

class Named {
  String name;
  Named(String name) {
    this.name = name;
  }
}

class Student extends Named {
  Student(String name) {
    Objects.requireNonNull(name);   // before !
    super(name);
  }
}

In the future, can initialize fields before super(...)

class A {
  A() {
    super();
    this.m();  // ooops !!!
  }
  void m() { }
}

class B extends A {
  int value;
  B(int value) {
    this.value = value;  // before !
    super();
  }
  @Override void m() {
    System.out.println(value);
  }
}

This second feature is not yet implemented !

Examples

Check preconditions before super(...)

• _1_precondition.java
• _2_precondition_record.java
• _3_less_readable.java

Initialize field before super(...)

• _4_this_escape.java
• _5_inner_class.java