public class Builder {
    public static void main(String[] args) {
        new ImmutableA.Builder().i(1).build();
    }
}

class ImmutableA {
    private final int i;
    private final String str;

    private ImmutableA(Builder builder) {
        i = builder.i;
        str = builder.str;
        System.out.println(i +" "+ str);
    }

    public static class Builder {
        private int i;
        private String str;

        public Builder i(int i) {
            this.i = i;
            return this;
        }

        public Builder str(String str) {
            this.str = str;
            return this;
        }

        public ImmutableA build() {
            return new ImmutableA(this);
        }
    }

}