Wie kann ich optionale Parameter in Java implementieren?

void foo(String a, Integer b) {
    //...
}

void foo(String a) {
    foo(a, 0); // Default value for b
}

foo("a", 2);
foo("a");

void foo(String a, Integer... b) {
    Integer b1 = b.length > 0 ? b[0] : 0;
    Integer b2 = b.length > 1 ? b[1] : 0;
    //...
}

foo("a");
foo("a", 1, 2);

void foo(String a, Integer b, Integer c) {
    b = b != null ? b : 0;
    c = c != null ? c : 0;
    //...
}

foo("a", null, 2);

void foo(String a, Optional<Integer> bOpt) {
    Integer b = bOpt.isPresent() ? bOpt.get() : 0;
    //...
}

foo("a", Optional.of(2));
foo("a", Optional.empty());

class Foo {
    private final String a; 
    private final Integer b;

    Foo(String a, Integer b) {
      this.a = a;
      this.b = b;
    }

    //...
}

class FooBuilder {
  private String a = ""; 
  private Integer b = 0;
  
  FooBuilder setA(String a) {
    this.a = a;
    return this;
  }

  FooBuilder setB(Integer b) {
    this.b = b;
    return this;
  }

  Foo build() {
    return new Foo(a, b);
  }
}

Foo foo = new FooBuilder().setA("a").build();

void foo(Map<String, Object> parameters) {
    String a = ""; 
    Integer b = 0;
    if (parameters.containsKey("a")) { 
        a = (String) parameters.get("a");
    }
    if (parameters.containsKey("b")) { 
        b = (Integer) parameters.get("b");
    }
    //...
}

foo(Map.of("a", "a", "b", 2, "d", "value"));