CompareTo（Object o）用于比较Java中的字符串

Question

In my program I'm trying to compare names by last name, and if those are the same then compare by using the first name. However, I can't quite figure out how to compare the strings.

Can someone help me out with this?

public class Student implements IComparable
{
String firstName;
String lastName;
int score;

public Student()
{

}

public void setFirstName(String firstName)
{
    this.firstName = firstName;
}
public String getFirstName()
{
    return firstName;
}

public void getLastName(String lastName)
{
    this.lastName = lastName;
}
public String getLastName()
{
    return lastName;
}

public void getScore(int score)
{
    this.score = score;
}
public int getScore()
{
    return score;
}

@Override
public int compareTo(Object o)
{
   //Compares Student objects by last name. If the last names are the same 
   //it compares by first name.
    Student s = (Student) o;

    if (this.getLastName().toUpperCase() < s.getLastName().toUpperCase())
        return -1;
    else if (this.getLastName().toUpperCase() > s.getLastName().toUpperCase())
        return 1;
    else
    {
        if(this.getFirstName().toUpperCase( < s.getFirstName().toUpperCase()
            return -1;
        else if (this.getFirstName().toUpperCase( > s.getFirstName().toUpperCase()
            return 1;
        else
            return 0;
    }
}
}

Answer 1

Don't make things more complicated:

• String class already provides compareToIgnoreCase method
• value returned by compare methods of String is already good to be directly returned

Basically the same functionality could be expressed with:

int compare = getLastName().compareToIgnoreCase(o.getLastName());
return compare == 0 ? getFirstName().compareToIgnoreCase(o.getFirstName()) : compare;

Mind that you need to check that o instanceof Student if you have an Object argument.

I don't get why you are using a custom IComparable interface, which sounds much like the one provided in C#, since Java provides Comparable<T> which is generic and doesn't require checking for the runtime type of the argument (since it's not Object anymore but T ).