Wote wawili hundefine jinsi ya kuagiza vitu, lakini kwa njia tofauti: Comparable hundefine agizo la asili la darasa (linalofanya kazi na darasa lenyewe), ilhali Comparator hundefine agizo la , mbadala (kitu tofauti). Chaguo linategemea kama agizo ni la ndani au la hali.
public class Person implements Comparable<Person> {
private String name;
private int age;
@Override
public int compareTo(Person other) { // defines THE natural order
return Integer.compare(this.age, other.age); // by age
}
// return: negative if this < other, 0 if equal, positive if this > other
}
List<Person> people = ...;
Collections.sort(people); // uses compareTo — sorts by age (the natural order)
Comparable inaishi ndani ya darasa kupitia compareTo(), ikitengeneza agizo lake la kawaida, linalojiweza tu. Inatumika kiotomatiki na Collections.sort, TreeSet, TreeMap, nk.
// define orderings OUTSIDE the class — as many as you need
Comparator<Person> byName = (a, b) -> a.getName().compareTo(b.getName());
Comparator<Person> byAge = Comparator.comparingInt(Person::getAge);
people.sort(byName); // sort by name
people.sort(byAge.reversed()); // by age, descending
Comparator ni kitu tofauti, kinachokukuruhusu kutengeneza agizo nyingi tofauti kwa darasa sawa bila kulichbadilisha.
Comparator<Person> comp = Comparator
.comparing(Person::getLastName) // primary: last name
.thenComparing(Person::getFirstName) // tie-break: first name
.thenComparingInt(Person::getAge) // then: age
.reversed(); // reverse the whole thing
people.sort(comp);
Mazo ya mtindo wa mungu comparing/thenComparing yanafanya upangaji tata wa sehemu nyingi kuwa muhimu na karibu kusomwa.
Comparable → the class has ONE obvious natural order (numbers by value, strings
alphabetically, dates chronologically); you own the class
Comparator → you need MULTIPLE orderings, situational/custom ordering, OR you
can't modify the class (e.g. sorting a third-party type differently)
Kuagiza vitu ni mahitaji ya kuendelea — kupanga orodha, kutumia TreeSet/TreeMap, kutafuta min/max.
Kufahamu tofauti ya Comparable-vs-Comparator kunakuruhusu kuchagua kwa usahihi: Comparable kwa agizo la kawaida la darasa moja (iliyojengwa, ilitumika kwa kawaida), Comparator kwa njia nzuri ya agizo nyingi au la nje (panga data sawa kwa njia tofauti, au agiza aina ambazo huwezi kudhibiti).
API ya Comparator ya kisasa na yenye mtiririko (comparing/thenComparing/reversed) inafanya upangaji wa anuwai nyingi kuwa nzuri.
Kuzifuata zote — na kila moja inapofaa — ni muhimu kwa kufanya kazi na miundo ya data iliyopangwa na ni mada inayorudiwa sana na ya vitendo na mahojiano katika Java.