Understanding syntax for compareto method in Java

Question

Below is my code implementation to sort by age-wise with compareTo method :

 public int compareTo(Student sNew)

    {

        return this.age-sNew.age;

    }

What is the use of “-”  in compareTo? 

Because here’s my code implementation without using “-” in compareTo method:

public int compareTo(Student sNew)

    {

        int returnValue=0;

        if(this.age>sNew.age)

        {

            returnValue=1;

        }else if(this.age<sNew.age){

            returnValue=-1;

        }else if(this.age==sNew.age)

        {

            returnValue=0;

        }

        return returnValue;

    }

Can anyone tell me what’s the use ‘-’ in compareTo operator and where it returns the value (0,1,-1) ? 

Answer 1

compareTo method doesn’t return (0,1,-1). It returns 1 if the string is greater than the compared string. It returns -1 if the string is less than the compared string. It returns 0 if both the strings are equal. 

The “-” will simply subtract the ages. 

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