#playground code on reading effective #java

Main.java

import java.util.ArrayList;

class DefaultValueInstanceVariable
{
    private int m;
    private int n; // IntelliJ warns "private field is never assigned".
    DefaultValueInstanceVariable(int x)
    {
        m = x;
    }
    void print()
    {
        System.out.println(m);
        System.out.println(n);
    }
}

class PromoteInt
{
    PromoteInt()
    {
        byte one = 1;
        byte two = 2;
        int three = one + two;
        Byte four = 4;
        Byte five = 5;
        Integer nine = four + five;
        double ten = 10;
    }
}

class SideEffect
{
    private static int id(int x)
    {
        System.out.println(x);
        return x;
    }
    static int f(int x)
    {
        id(0);
        return id(x);
    }
}

class ThisConstructor
{
    int x;
    ThisConstructor(int x)
    {
        this.x = x;
    }
    ThisConstructor(int x, int y)
    {
        this(x + y);
    }
}

//public class ZeroOrOnePublicClass {}

class RemoveRange
{
    public static void removeRange()
    {
        ArrayList<Integer> arrayList = new ArrayList<Integer>();
        arrayList.add(1);
        arrayList.add(2);
        arrayList.add(3);
        arrayList.add(4);
        arrayList.add(5);
        arrayList.add(6);
        arrayList.subList(1, 4).add(10);
        System.out.println(arrayList.subList(1, 4));
        System.out.println(arrayList);
    }
}

enum Singleton {
    instance
}

class utility
{
    public static void print()
    {
        System.out.println("hello");
    }
}

public class Main {

    public static void main(String[] args) {
        System.out.println("Hello World!");
        DefaultValueInstanceVariable defaultValueInstanceVariable = new DefaultValueInstanceVariable(1);
        defaultValueInstanceVariable.print();
        SideEffect.f(2);
        ThisConstructor thisConstructor = new ThisConstructor(1, 2);
        System.out.println(thisConstructor.x);
        RemoveRange.removeRange();
        NutritionFacts cocaCola = NutritionFacts.build(240, 8).calories(100).sodium(35).carbohydrate(27).build();
        System.out.println(Singleton.instance);
        utility.print();
    }
}

NutritionFacts.java

public class NutritionFacts
{
    private final int servingSize;
    private final int servings;
    private final int calories;
    private final int fat;
    private final int sodium;
    private final int carbohydrate;

    public static class Internal
    {
        // Parameters initialized to default values (if any)
        private int servingSize; // Required; no default value
        private int servings;    // " " " "
        private int calories     = 0;
        private int fat          = 0;
        private int sodium       = 0;
        private int carbohydrate = 0;

        private Internal(int servingSize, int servings)
        {
            this.servingSize = servingSize;
            this.servings = servings;
        }

        // Setters
        public Internal calories(int val)
        {
            calories = val;
            return this;
        }

        public Internal fat(int val)
        {
            fat = val;
            return this;
        }

        public Internal sodium(int val)
        {
            sodium = val;
            return this;
        }

        public Internal carbohydrate(int val)
        {
            carbohydrate = val;
            return this;
        }

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

    private NutritionFacts(Internal internal)
    {
        servingSize = internal.servingSize;
        servings = internal.servings;
        calories = internal.calories;
        fat = internal.fat;
        sodium = internal.sodium;
        carbohydrate = internal.carbohydrate;
    }

    public static Internal build(int servingSize, int servings)
    {
        Internal internal = new Internal(servingSize, servings);
        return internal;
    }

}