我有一个包含国家名称的List<String>对象。我如何按字母顺序对这个列表排序?
当前回答
迟到总比不到好!以下是我们如何做(仅供学习之用)
import java.util.List;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
class SoftDrink {
String name;
String color;
int volume;
SoftDrink (String name, String color, int volume) {
this.name = name;
this.color = color;
this.volume = volume;
}
}
public class ListItemComparision {
public static void main (String...arg) {
List<SoftDrink> softDrinkList = new ArrayList<SoftDrink>() ;
softDrinkList .add(new SoftDrink("Faygo", "ColorOne", 4));
softDrinkList .add(new SoftDrink("Fanta", "ColorTwo", 3));
softDrinkList .add(new SoftDrink("Frooti", "ColorThree", 2));
softDrinkList .add(new SoftDrink("Freshie", "ColorFour", 1));
Collections.sort(softDrinkList, new Comparator() {
@Override
public int compare(Object softDrinkOne, Object softDrinkTwo) {
//use instanceof to verify the references are indeed of the type in question
return ((SoftDrink)softDrinkOne).name
.compareTo(((SoftDrink)softDrinkTwo).name);
}
});
for (SoftDrink sd : softDrinkList) {
System.out.println(sd.name + " - " + sd.color + " - " + sd.volume);
}
Collections.sort(softDrinkList, new Comparator() {
@Override
public int compare(Object softDrinkOne, Object softDrinkTwo) {
//comparision for primitive int uses compareTo of the wrapper Integer
return(new Integer(((SoftDrink)softDrinkOne).volume))
.compareTo(((SoftDrink)softDrinkTwo).volume);
}
});
for (SoftDrink sd : softDrinkList) {
System.out.println(sd.volume + " - " + sd.color + " - " + sd.name);
}
}
}
其他回答
Java 8,
countries.sort((country1, country2) -> country1.compareTo(country2));
如果String的compareTo不适合您的需要,您可以提供任何其他比较器。
JAVA 8相同:-
//Assecnding order
listOfCountryNames.stream().sorted().forEach((x) -> System.out.println(x));
//Decending order
listOfCountryNames.stream().sorted((o1, o2) -> o2.compareTo(o1)).forEach((x) -> System.out.println(x));
//Here is sorted List alphabetically with syncronized
package com.mnas.technology.automation.utility;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.Iterator;
import java.util.List;
import org.apache.log4j.Logger;
/**
*
* @author manoj.kumar
*/
public class SynchronizedArrayList {
static Logger log = Logger.getLogger(SynchronizedArrayList.class.getName());
@SuppressWarnings("unchecked")
public static void main(String[] args) {
List<Employee> synchronizedList = Collections.synchronizedList(new ArrayList<Employee>());
synchronizedList.add(new Employee("Aditya"));
synchronizedList.add(new Employee("Siddharth"));
synchronizedList.add(new Employee("Manoj"));
Collections.sort(synchronizedList, new Comparator() {
public int compare(Object synchronizedListOne, Object synchronizedListTwo) {
//use instanceof to verify the references are indeed of the type in question
return ((Employee)synchronizedListOne).name
.compareTo(((Employee)synchronizedListTwo).name);
}
});
/*for( Employee sd : synchronizedList) {
log.info("Sorted Synchronized Array List..."+sd.name);
}*/
// when iterating over a synchronized list, we need to synchronize access to the synchronized list
synchronized (synchronizedList) {
Iterator<Employee> iterator = synchronizedList.iterator();
while (iterator.hasNext()) {
log.info("Sorted Synchronized Array List Items: " + iterator.next().name);
}
}
}
}
class Employee {
String name;
Employee (String name) {
this.name = name;
}
}
更简单地说,您可以使用方法引用。
list.sort(String::compareTo);
通过使用Collections.sort(),我们可以对列表进行排序。
public class EmployeeList {
public static void main(String[] args) {
// TODO Auto-generated method stub
List<String> empNames= new ArrayList<String>();
empNames.add("sudheer");
empNames.add("kumar");
empNames.add("surendra");
empNames.add("kb");
if(!empNames.isEmpty()){
for(String emp:empNames){
System.out.println(emp);
}
Collections.sort(empNames);
System.out.println(empNames);
}
}
}
输出:
sudheer
kumar
surendra
kb
[kb, kumar, sudheer, surendra]