// package classes;

public class TimeSpan {

    private int hours;
    private int minutes;

    // Construtor to pass hours and minutes
    public TimeSpan(int hours, int minutes) {
        this.hours = 0;
        this.minutes = 0;
        add(hours, minutes);
    }
    
    

    // this methods thorws an error if invalid hours and miutes passes into the
    // argument
    public void add(int hours, int minutes) {
        if (hours < 0 || minutes < 0) {
            throw new IllegalArgumentException();
        }

        this.hours += hours;
        this.minutes += minutes;

        // converts each 60 minutes into one hour
        this.hours += this.minutes / 60;
        this.minutes = this.minutes % 60;
    }




// multiple the time with factor
    public void scale(int factor) {
        // this makes sure it throws illegal argument exception
        if(factor<0)
           throw new IllegalArgumentException();
        
        // calculate the minutes and multiply with factor
        this.minutes = (((this.hours*60+this.minutes))*factor)%60;
        // calculate by dividing with 60 you will get total hours
        this.hours  = (((this.hours*60+this.minutes))*factor)/60;

    }

    // returns a String for this time span, such as "6h 15m"
    public String toString() {
        return hours + "h " + minutes + "m";
    }



public static void main(String[] args) {

        TimeSpan elapsed = new TimeSpan(2, 6);
        
        TimeSpan elapsed2 = new TimeSpan(2, 56);

        System.out.println("elapsed time before scale: " + elapsed);
        
        elapsed.scale(2);
        

        System.out.println("elapsed time after scalling with factor: " + elapsed);

    }

}



Output:


elapsed time before scale: 2h 6m
elapsed time after scalling with factor: 4h 12m