Java Programming: How to use compareTo when comparing the names of the candidates in a text document

Question

This method is used to compare the names of two candidates. Returns 0 if the name of this candidate is the same as the name of otherCan; returns < 0 if the name of this candidate is less then the name of otherCan; returns > 0 if the name of this candidate is greater than the name of otherCan.

@Override
    public int compareTo(Candidate otherCan) {
        if(name = otherCan){
        return this.name.compareToIgnoreCase(otherCan.getName());
    } else if(name < otherCan){
            return name < 0
        } else if(name > otherCan){
        return name > 0
        }
}

How do I compare them and what does return > 0 and < 0 mean?

possible duplicate of http://stackoverflow.com/questions/3718383/why-should-a-java-class-implement-comparable — ControlAltDel, Dec 15 '16 at 20:53
`if(name = otherCan){` is wrong; it needs to be `if(name == otherCan){`. The single `=` is for assigning a value; the double is for comparing two things. — NRitH, Dec 15 '16 at 20:56
@Override public int compareTo(Candidate otherCan) { return this.name.compareToIgnoreCase(otherCan.getName()); } — E.A, Dec 15 '16 at 20:59

score 1 · Accepted Answer · answered Dec 15 '16 at 21:02

There are many problems with this example.

    public int compareTo(Candidate otherCan) {
        if(name = otherCan){

As I pointed out in a comment, this must be ==; otherwise, you're assigning the value of otherCan to name.

        return this.name.compareToIgnoreCase(otherCan.getName());

If name == otherCan is true, then this call will always return 0.

    } else if(name < otherCan){
            return name < 0

This line shouldn't compile because it's trying to return a boolean in a method that return an int.

        } else if(name > otherCan){
        return name > 0

Same as the previous note; this shouldn't compile. } }

This entire method is unnecessary. Just calling name.compareToIgnoreCase(otherCan.getName()) is enough, as it will return 0 if the strings are equal, a negative number (not necessarily -1) if the first string comes before the second in sorted order, and a positive number if the second string should come first.

Thank you so much for confirmation. I was confused, but thank you so much for your help!!! — E.A, Dec 15 '16 at 21:06

Java Programming: How to use compareTo when comparing the names of the candidates in a text document

1 Answers1