Scala namespaces for definitions

Scala has just two namespaces for definitions in place of Java’s four. Java’s namespaces are fields, methods, types, and packages. Scala’s namespaces are:
• values (fields, methods, packages, and singleton objects)
• types (class and trait names)

In Scala it is forbidden to define a field and method with the same name in the same class, whereas it is allowed in Java.
This Java class would compile just fine:


class CompilesFine {
  private int f = 0;
  public int f() {
    return 1;
  }
}

But the corresponding Scala class would not compile:

class WontCompile {
  private var f = 0
  def f = 1
}

The reason Scala places fields and methods into the same namespace is precisely so you can override a parameterless method with a val.
Source: Overriding methods and fields