Статьи

Пять полезных способов сортировки в Java

Апрель 24, 2019

Быстрый обзор сортировки Java:

обычный вид списка:

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private static List VEGETABLES = Arrays.asList("apple", "cocumbers", "blackberry");
Collections.sort(VEGETABLES);
 
output: apple, blackberry, cocumbers

Обратная сортировка:

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private static List VEGETABLES = Arrays.asList("apple", "cocumbers", "blackberry");
Collections.sort(VEGETABLES, Collections.reverseOrder());
output: cocumbers, blackberry, apple

с пользовательским компаратором:

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private class StringComparator implements Comparator {
          public int compare(Object o1, Object o2) {
              String so1 = (String) o1;
  String so2 = (String) o2;
  return so1.compareTo(so2);
  }
 }
private static List VEGETABLES = Arrays.asList("apple", "cocumbers", "blackberry");
Collections.sort(VEGETABLES, new StringComparator());
output: apple, blackberry, cocumbers

Сортировка элементов:

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private class Element implements Comparable {
             private String name;
             private Double atomicMass;
         
             @Override
              public String toString() {
                  final StringBuilder sb = new StringBuilder();
                  sb.append("Element");
                  sb.append("{name='").append(name).append('\'');
                  sb.append(", atomicMass=").append(atomicMass);
                  sb.append('}');
                  return sb.toString();
              }
         
              public String getName() {
                  return name;
              }
        
              public void setName(String name) {
                  this.name = name;
              }
        
              public Double getAtomicMass() {
                  return atomicMass;
              }
        
              public void setAtomicMass(Double atomicMass) {
                  this.atomicMass = atomicMass;
              }
       
              public Element(String name, String mass, double atomicMass) {
                  this.name = name;
                  this.atomicMass = atomicMass;
              }
       
              public int compareTo(Element o) {
                  return this.getAtomicMass().compareTo(o.getAtomicMass());
              }
          }
        
          ArrayList<Element> elements = new ArrayList<Element>();
          elements.add(new Element("Hydrogen", "H", 1.00794)); // Hydrogen 1.00794 amu Atomic Mass
          elements.add(new Element("Iron", "Fe", 55.845));
          elements.add(new Element("Lithium", "Li", 6.941));
          elements.add(new Element("Lead", "Pb", 207.2));
          elements.add(new Element("Magnesium", "Mg", 24.305));
          Collections.sort(elements);   // Sort by Element

выход:

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Element{name='Hydrogen', atomicMass=1.00794}
         Element{name='Lithium', atomicMass=6.941}
         Element{name='Magnesium', atomicMass=24.305}
         Element{name='Iron', atomicMass=55.845}
         Element{name='Lead', atomicMass=207.2}

Хронологическая сортировка:

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SimpleDateFormat formatter = new SimpleDateFormat("MMMM dd, yyyy", Locale.US);
      try {
 ArrayList<Date> holidays = new ArrayList<Date>();
          holidays.add(formatter.parse("May 31, 2010")); //  Memorial Day
          holidays.add(formatter.parse("July 4, 2010")); //  Independence Day
          holidays.add(formatter.parse("February 15, 2010")); //  Presidents Day
          holidays.add(formatter.parse("September 6, 2010")); // Labor Day
          holidays.add(formatter.parse("December 24, 2010")); // Thanksgiving Day
          holidays.add(formatter.parse("July 5, 2010")); //  federal employees extra day off for July 4th
          holidays.add(formatter.parse("January 18, 2010")); //  Martin Luther King Day
          holidays.add(formatter.parse("November 25, 2010")); // federal employees extra day off for Christmas
          holidays.add(formatter.parse("October 11, 2010")); // Columbus Day
          holidays.add(formatter.parse("December 25, 2010")); // Christmas Day
          holidays.add(formatter.parse("January 1, 2010")); // New Year's Day
          Collections.sort(holidays);  // Native sort for Date is chronological
          
          } catch (ParseException e) {
              e.printStackTrace();
          }

выход:

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sorted:[Fri Jan 01 00:00:00 CET 2010, Mon Jan 18 00:00:00 CET 2010, Mon Feb 15 00:00:00 CET 2010, Mon May 31 00:00:00 CEST 2010, Sun Jul 04 00:00:00 CEST 2010, Mon Jul 05 00:00:00 CEST 2010, Mon Sep 06 00:00:00 CEST 2010, Mon Oct 11 00:00:00 CEST 2010, Thu Nov 25 00:00:00 CET 2010, Fri Dec 24 00:00:00 CET 2010, Sat Dec 25 00:00:00 CET 2010]

Вы можете просмотреть полный простой класс ниже:

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package com.tommyalf.personal.sorting;
 
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.*;
 
/**
* Created by IntelliJ IDEA.
* User: tommyalf
* Date: 1-dic-2010
* Time: 22.40.49
*/
public class SortDemo {
    private static List VEGETABLES = Arrays.asList("apple", "cocumbers", "blackberry");;
 
 
    public static void main(String args[]) {
        SortDemo sd = new SortDemo();
        sd.normalSort();
        sd.reverseSort();
        sd.stringComparator();
        sd.elementsSort();
        sd.chronologicalSort();
    }
 
    private void chronologicalSort() {
        SimpleDateFormat formatter = new SimpleDateFormat("MMMM dd, yyyy", Locale.US);
        try {
            ArrayList<Date> holidays = new ArrayList<Date>();
            holidays.add(formatter.parse("May 31, 2010")); // Memorial Day
            holidays.add(formatter.parse("July 4, 2010")); // Independence Day
            holidays.add(formatter.parse("February 15, 2010")); // Presidents Day
            holidays.add(formatter.parse("September 6, 2010")); // Labor Day
            holidays.add(formatter.parse("December 24, 2010")); // Thanksgiving Day
            holidays.add(formatter.parse("July 5, 2010")); // federal employees extra day off for July 4th
            holidays.add(formatter.parse("January 18, 2010")); // Martin Luther King Day
            holidays.add(formatter.parse("November 25, 2010")); // federal employees extra day off for Christmas
            holidays.add(formatter.parse("October 11, 2010")); // Columbus Day
            holidays.add(formatter.parse("December 25, 2010")); // Christmas Day
            holidays.add(formatter.parse("January 1, 2010")); // New Year's Day
            System.out.println("before sort:" + holidays);
            Collections.sort(holidays); // Native sort for Date is chronological
            System.out.println("sorted:" + holidays);
        } catch (ParseException e) {
            e.printStackTrace();
        }
    }
 
    private void elementsSort() {
        ArrayList<Element> elements = new ArrayList<Element>();
        elements.add(new Element("Hydrogen", "H", 1.00794)); // Hydrogen 1.00794 amu Atomic Mass
        elements.add(new Element("Iron", "Fe", 55.845));
        elements.add(new Element("Lithium", "Li", 6.941));
        elements.add(new Element("Lead", "Pb", 207.2));
        elements.add(new Element("Magnesium", "Mg", 24.305));
        Collections.sort(elements); // Sort by Element
        System.out.print("Elements sort by atomicMass value:");
        for ( Element e : elements ) {
           System.out.println(e);
        }
    }
 
    private void stringComparator() {
        Collections.sort(VEGETABLES, new StringComparator());
        System.out.print("StringComparator:");
        printList(VEGETABLES);
    }
 
    private void reverseSort() {
        Collections.sort(VEGETABLES, Collections.reverseOrder());
        System.out.print("ReverseSort:");
        printList(VEGETABLES);
    }
 
    private void normalSort() {
        Collections.sort(VEGETABLES);
        System.out.print("NormalSort:");
        printList(VEGETABLES);
    }
 
    private void printList(List vegetables) {
        for (int i = 0, n = vegetables.size(); i < n; i++) {
            if (i != 0) {
                System.out.print(", ");
            }
            System.out.print(VEGETABLES.get(i));
        }
        System.out.println();
    }
 
    private class StringComparator implements Comparator {
        public int compare(Object o1, Object o2) {
            String so1 = (String) o1;
            String so2 = (String) o2;
            return so1.compareTo(so2);
        }
    }
 
    private class Element implements Comparable<Element> {
        private String name;
        private Double atomicMass;
 
        @Override
        public String toString() {
            final StringBuilder sb = new StringBuilder();
            sb.append("Element");
            sb.append("{name='").append(name).append('\'');
            sb.append(", atomicMass=").append(atomicMass);
            sb.append('}');
            return sb.toString();
        }
 
        public String getName() {
            return name;
        }
 
        public void setName(String name) {
            this.name = name;
        }
 
        public Double getAtomicMass() {
            return atomicMass;
        }
 
        public void setAtomicMass(Double atomicMass) {
            this.atomicMass = atomicMass;
        }
 
        public Element(String name, String mass, double atomicMass) {
            this.name = name;
            this.atomicMass = atomicMass;
        }
 
 
        public int compareTo(Element o) {
            return this.getAtomicMass().compareTo(o.getAtomicMass());
        }
    }
}

Ссылка: Пять полезных способов сортировки в java от нашего партнера JCG Томми Альфа в

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