I want to use Collections.sort() twice on two different parameters [duplicate]

Question

I have a list of objects that I want to sort using different properties.

@Override
public int compareTo(Object obj)
{
    Field tab = (Field) obj;

    int objx = Integer.parseInt(tab.getX());
    // int objy = Integer.parseInt(tab.getY());

    int classX = Integer.parseInt(this.X);

    if (classX == objx)
      return 0;
    else if (classX > objx)
      return 1;
    else
      return -1;
}

What I have so far:

Collections.sort(list1); // But using property1 to sort
Collections.sort(list1); // But using property2 to sort

So, in first case I'm able to sort using property1, but how to sort using property2? I'm trying to sort using different parameters, but compareTo() accepts only one.

Answer 1

If you want to use two different property you need to use two different comparators.

A comparator is a class that implements the interface Comparator

public class EmpSort {
    static final Comparator<Employee> comp1 = new Comparator<Employee>() {
        public int compare(Employee e1, Employee e2) {
            // use prperty1 to sort
            return e2.hireDate().compareTo(e1.hireDate());
        }
    };
}
public class EmpSort2 {
    static final Comparator<Employee> comp2 = new Comparator<Employee>() {
        public int compare(Employee e1, Employee e2) {
            // use prperty2 to sort
            return e2.hireDate().compareTo(e1.hireDate());
        }
    };
}

Collections.sort(list1, comp1);//but using prperty1 to sort
Collections.sort(list1, comp2);//but using prperty2 to sort

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