Builder Pattern in Effective Java

Question

Make the builder a static class. Then it will work. If it is non-static, it would require an instance of its owning class - and the point is not to have an instance of it, and even to forbid making instances without the builder.

public class NutritionFacts {
    public static class Builder {
    }
}

Reference: Nested classes

You should make the Builder class as static and also you should make the fields final and have getters to get those values. Don't provide setters to those values. In this way your class will be perfectly immutable.

public class NutritionalFacts {
    private final int sodium;
    private final int fat;
    private final int carbo;

    public int getSodium(){
        return sodium;
    }

    public int getFat(){
        return fat;
    }

    public int getCarbo(){
        return carbo;
    }

    public static class Builder {
        private int sodium;
        private int fat;
        private int carbo;

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

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

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

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

    private NutritionalFacts(Builder b) {
        this.sodium = b.sodium;
        this.fat = b.fat;
        this.carbo = b.carbo;
    }
}

And now you can set the properties as follows:

NutritionalFacts n = new NutritionalFacts.Builder().sodium(10).carbo(15).
fat(5).build();

To generate an inner builder in Intellij IDEA, check out this plugin: https://github.com/analytically/innerbuilder

You are trying access a non-static class in a static way. Change Builder to static class Builder and it should work.

The example usage you give fails because there is no instance of Builder present. A static class for all practical purposes is always instantiated. If you don't make it static, you'd need to say:

Widget = new Widget.Builder(10).setparm1(1).setparm2(3).build();

Because you would need to construct a new Builder every time.

You need to declare the Builder inner class as static.

Consult some documentation for both non-static inner classes and static inner classes.

Basically the non-static inner classes instances cannot exist without attached outer class instance.