compare and sort different type of objects using java Collections

Question

How to compare and sort different type of objects using java Collections .Below is the use case: For example DOG,MAN,TREE, COMPUTER,MACHINE - all these different objects has a common property say "int lifeTime". Now I want to order these obects based on the lifeTime property

Thx

Answer 1

All of these objects should have a common abstract class/interface such as Alive with a method getLifeTime(), and you could have either Alive extends Comparable<Alive> or create your own Comparator<Alive>.

public abstract class Alive extends Comparable<Alive>{
    public abstract int getLifeTime();
    public int compareTo(Alive alive){
        return 0; // Or a negative number or a positive one based on the getLifeTime() method
    }
}

Or

public interface Alive {
    int getLifeTime();
}

public class AliveComparator implements Comparator<Alive>{
    public int compare(Alive alive1, Alive alive2){
        return 0; // Or a negative number or a positive one based on the getLifeTime() method
    }
}

After that the next step is to use either an automatically sorted collection (TreeSet<Alive>) or sort a List<Alive> with Collections.sort().

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Resources :

• Javadoc - Collections.sort()
• Javadoc - Comparable
• Javadoc - Comparator