sort - ordenar una lista de numeros en java

Android-java- Cómo ordenar una lista de objetos por un cierto valor dentro del objeto

Question

Estoy tratando de ordenar a través de una lista de objetos por un valor particular dentro del objeto. ¿Cuál sería el mejor enfoque para hacer tal cosa? ¿Debo usar Collections.sort () con algún tipo de comparador?

Estoy tratando de ordenar una lista de objetos por un valor flotante que tienen en una de las variables.

EDITAR: Esto es lo que tengo hasta ahora:

public class CustomComparator implements Comparator<Marker> {
@Override
public int compare(Mark o1, Mark o2) {
return o1.getDistance().compareTo(o2.getDistance());
}
}

los estados de error: No se puede invocar compareTo (double) en el tipo primitivo double.

¿Es porque un comparador no puede devolver nada que no sea un cierto tipo?

Answer 1

"Android-java" está aquí de ninguna manera diferente a "java normal", así que sí Collections.sort() sería un buen enfoque.

Answer 2

Ahora no hay necesidad de boxeo (es decir, no hay necesidad de crear OBJECT utilizando el nuevo valor de uso del operador de Insteted with compareTo de Collections.Sort ..)

1) Por orden ascendente

Collections.sort(temp, new Comparator<XYZBean>()
{
@Override
public int compare(XYZBean lhs, XYZBean rhs) {
return Integer.valueOf(lhs.getDistance()).compareTo(rhs.getDistance());
}
});

1) Para orden descendente

Collections.sort(temp, new Comparator<XYZBean>()
{
@Override
public int compare(XYZBean lhs, XYZBean rhs) {
return Integer.valueOf(rhs.getDistance()).compareTo(lhs.getDistance());
}
});

Answer 3

Creo que esto te ayudará a mejorar

Person p = new Person("Bruce", "Willis");
Person p1 = new Person("Tom", "Hanks");
Person p2 = new Person("Nicolas", "Cage");
Person p3 = new Person("John", "Travolta");
ArrayList<Person> list = new ArrayList<Person>();
list.add(p);
list.add(p1);
list.add(p2);
list.add(p3);
Collections.sort(list, new Comparator() {
@Override
public int compare(Object o1, Object o2) {
Person p1 = (Person) o1;
Person p2 = (Person) o2;
return p1.getFirstName().compareToIgnoreCase(p2.getFirstName());
}
});

Answer 4

Debe usar Comparable en lugar de un Comparador si lo que busca es una clasificación predeterminada.

Vea aquí, esto puede ser de alguna ayuda - ¿ Cuándo debería una clase ser Comparable y / o Comparador?

Prueba esto -

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
public class TestSort {
public static void main(String args[]){
ToSort toSort1 = new ToSort(new Float(3), "3");
ToSort toSort2 = new ToSort(new Float(6), "6");
ToSort toSort3 = new ToSort(new Float(9), "9");
ToSort toSort4 = new ToSort(new Float(1), "1");
ToSort toSort5 = new ToSort(new Float(5), "5");
ToSort toSort6 = new ToSort(new Float(0), "0");
ToSort toSort7 = new ToSort(new Float(3), "3");
ToSort toSort8 = new ToSort(new Float(-3), "-3");
List<ToSort> sortList = new ArrayList<ToSort>();
sortList.add(toSort1);
sortList.add(toSort2);
sortList.add(toSort3);
sortList.add(toSort4);
sortList.add(toSort5);
sortList.add(toSort6);
sortList.add(toSort7);
sortList.add(toSort8);
Collections.sort(sortList);
for(ToSort toSort : sortList){
System.out.println(toSort.toString());
}
}
}
public class ToSort implements Comparable<ToSort> {
private Float val;
private String id;
public ToSort(Float val, String id){
this.val = val;
this.id = id;
}
@Override
public int compareTo(ToSort f) {
if (val.floatValue() > f.val.floatValue()) {
return 1;
}
else if (val.floatValue() < f.val.floatValue()) {
return -1;
}
else {
return 0;
}
}
@Override
public String toString(){
return this.id;
}
}

Answer 5

Haga un Comparator que pueda comparar sus objetos, o si son todos ejemplares de la misma clase, puede hacer que esa clase implemente Comparable . Luego puede usar Collections.sort () para hacer la clasificación real.

Answer 6

Puedes comparar dos cadenas usando esto.

Collections.sort(contactsList, new Comparator<ContactsData>() {
@Override
public int compare(ContactsData lhs, ContactsData rhs) {
char l = Character.toUpperCase(lhs.name.charAt(0));
if (l < ''A'' || l > ''Z'')
l += ''Z'';
char r = Character.toUpperCase(rhs.name.charAt(0));
if (r < ''A'' || r > ''Z'')
r += ''Z'';
String s1 = l + lhs.name.substring(1);
String s2 = r + rhs.name.substring(1);
return s1.compareTo(s2);
}
});

Y ahora crea una clase ContactData.

public class ContactsData {
public String name;
public String id;
public String email;
public String avatar;
public String connection_type;
public String thumb;
public String small;
public String first_name;
public String last_name;
public String no_of_user;
public int grpIndex;
public ContactsData(String name, String id, String email, String avatar, String connection_type)
{
this.name = name;
this.id = id;
this.email = email;
this.avatar = avatar;
this.connection_type = connection_type;
}
}

Aquí contactsList es:

public static ArrayList<ContactsData> contactsList = new ArrayList<ContactsData>();

Answer 7

Siga este código para ordenar cualquier ArrayList

Collections.sort(myList, new Comparator<EmployeeClass>(){
public int compare(EmployeeClass obj1, EmployeeClass obj2) {
// ## Ascending order
return obj1.firstName.compareToIgnoreCase(obj2.firstName); // To compare string values
// return Integer.valueOf(obj1.empId).compareTo(obj2.empId); // To compare integer values
// ## Descending order
// return obj2.firstName.compareToIgnoreCase(obj1.firstName); // To compare string values
// return Integer.valueOf(obj2.empId).compareTo(obj1.empId); // To compare integer values
}
});

Answer 8

Tengo una vista de lista que muestra la información sobre todos los clientes. Estoy ordenando el nombre de los clientes usando esta clase de comparador personalizado. Tienen algo de lerret extra aparte de las letras inglesas que estoy administrando con este setStrength (Collator.SECONDARY)

 public class CustomNameComparator implements Comparator<ClientInfo> {
@Override
public int compare(ClientInfo o1, ClientInfo o2) {
Locale locale=Locale.getDefault();
Collator collator = Collator.getInstance(locale);
collator.setStrength(Collator.SECONDARY);
return collator.compare(o1.title, o2.title);
}
}
PRIMARY strength: Typically, this is used to denote differences between base characters (for example, "a" < "b"). It is the strongest difference. For example, dictionaries are divided into different sections by base character.
SECONDARY strength: Accents in the characters are considered secondary differences (for example, "as" < "às" < "at"). Other differences between letters can also be considered secondary differences, depending on the language. A secondary difference is ignored when there is a primary difference anywhere in the strings.
TERTIARY strength: Upper and lower case differences in characters are distinguished at tertiary strength (for example, "ao" < "Ao" < "aò"). In addition, a variant of a letter differs from the base form on the tertiary strength (such as "A" and "Ⓐ"). Another example is the difference between large and small Kana. A tertiary difference is ignored when there is a primary or secondary difference anywhere in the strings.
IDENTICAL strength: When all other strengths are equal, the IDENTICAL strength is used as a tiebreaker. The Unicode code point values of the NFD form of each string are compared, just in case there is no difference. For example, Hebrew cantellation marks are only distinguished at this strength. This strength should be used sparingly, as only code point value differences between two strings are an extremely rare occurrence. Using this strength substantially decreases the performance for both comparison and collation key generation APIs. This strength also increases the size of the collation key.
**Here is a another way to make a rule base sorting if u need it just sharing**
/* String rules="< å,Å< ä,Ä< a,A< b,B< c,C< d,D< é< e,E< f,F< g,G< h,H< ï< i,I"+"< j,J< k,K< l,L< m,M< n,N< ö,Ö< o,O< p,P< q,Q< r,R"+"< s,S< t,T< ü< u,U< v,V< w,W< x,X< y,Y< z,Z";
RuleBasedCollator rbc = null;
try {
rbc = new RuleBasedCollator(rules);
} catch (ParseException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
String myTitles[]={o1.title,o2.title};
Collections.sort(Arrays.asList(myTitles), rbc);*/

Answer 9

Clase de modelo:

public class ToDoModel implements Comparable<ToDoModel> {
private String id;
private Date taskDate;
public String getId() {
return id;
}
public void setId(String id) {
this.id = id;
}
public Date getTaskDate() {
return taskDate;
}
public void setTaskDate(Date taskDate) {
this.taskDate = taskDate;
}
@Override
public int compareTo(ToDoModel another) {
return getTaskDate().compareTo(another.getTaskDate());
}
}

Ahora establece los datos en ArrayList

for (int i = 0; i < your_array_length; i++) {
ToDoModel tm = new ToDoModel();
tm.setId(your_id);
tm.setTaskDate(your_date);
mArrayList.add(tm);
}

Ahora Sort ArrayList

Collections.sort(toDoList);

Resumen: ordenará sus datos en fecha

Answer 10

public class DateComparator implements Comparator<Marker> {
@Override
public int compare(Mark lhs, Mark rhs) {
Double distance = Double.valueOf(lhs.getDistance());
Double distance1 = Double.valueOf(rhs.getDistance());
if (distance.compareTo(distance1) < 0) {
return -1;
} else if (distance.compareTo(distance1) > 0) {
return 1;
} else {
return 0;
}
}
}
ArrayList(Marker) arraylist;

Cómo utilizar:

Collections.sort(arraylist, new DateComparator());