gistfile1.java

/**
 * A simple Java data class with two immutable fields.  If I want
 * to add a third field (e.g. seconds), I have to update a ton of
 * places and remember them all, because a compiler will not tell
 * you what you missed.  If I generate equals/hashCode/toString, I
 * have to remember to do so with every change.  And I cannot 
 * overload constructors and assume default values for parameters,
 * because in this class, each field is an int and they'd have the
 * same signature, so I have to use the Builder Pattern to do 
 * default values.  This is a maintenance nightmare compared to
 * the equivalent Scala case class code:
 * 
 *   case class TimeImpl(hours: Int = 0, minutes: Int = 0)
 */
public class TimeImpl implements Time 
{ 
    private final int hours;
    private final int minutes;

    public TimeImpl(int hours, int minutes) 
    {
        this.hours = hours;
        this.minutes = minutes;
    }

    public int getHours() 
    {
        return hours;
    }

    public int getMinutes() 
    {
        return minutes;
    }

    @Override  
    public boolean equals(Object obj) 
    {  
        if (obj == null) 
        {  
            return false;  
        }  
        if (getClass() != obj.getClass()) 
        {  
            return false;  
        }
        
        final TimeImpl other = (TimeImpl)obj;
        return com.google.common.base.Objects.equal(this.hours, other.hours)  
            && com.google.common.base.Objects.equal(this.minutes, other.minutes);
    }  
  
    @Override  
    public int hashCode() 
    {  
        return com.google.common.base.Objects.hashCode(this.hours, this.minutes);  
    }  
  
    @Override  
    public String toString() 
    {  
        return com.google.common.base.Objects.toStringHelper(this)  
                .addValue(this.hours)  
                .addValue(this.minutes)  
                .toString();  
    }

    public static class TimeBuilder 
    {
        private int hours = 0;
        private int minutes = 0;
    
        public TimeBuilder() 
        {
        }

        public TimeBuilder setHours(int hours) 
        {
            this.hours = hours;
        }

        public TimeBuilder setMinutes(int minutes) 
        {
            this.minutes = minutes;
        }

        public Time build() 
        {
            return new TimeImpl(this);
        }
    }
}