2 ways to implement arguments with default values in Java methods

defaultValues.java

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

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

public class FooBuilder {
    private String a = "";
    private Integer b = 0;

    public FooBuilder setA(String a) {
        this.a = a;
        return this;
    }

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

    public Foo build() {
        return new Foo(a, b);
    }
}
Foo foo = new FooBuilder().setA("a").build();