用Java排序的五种有用方法

Java排序快速概述：

正常的列表：

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

反向排序：

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

使用自定义比较器：

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

元素排序：

private class Element implements Comparable {private String name;private Double atomicMass;@Overridepublic 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 Masselements.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

输出：

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}

按时间排序：

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

输出：

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]

您可以在下面查看完整的简单类：

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 Dayholidays.add(formatter.parse("July 4, 2010")); // Independence Dayholidays.add(formatter.parse("February 15, 2010")); // Presidents Dayholidays.add(formatter.parse("September 6, 2010")); // Labor Dayholidays.add(formatter.parse("December 24, 2010")); // Thanksgiving Dayholidays.add(formatter.parse("July 5, 2010")); // federal employees extra day off for July 4thholidays.add(formatter.parse("January 18, 2010")); // Martin Luther King Dayholidays.add(formatter.parse("November 25, 2010")); // federal employees extra day off for Christmasholidays.add(formatter.parse("October 11, 2010")); // Columbus Dayholidays.add(formatter.parse("December 25, 2010")); // Christmas Dayholidays.add(formatter.parse("January 1, 2010")); // New Year's DaySystem.out.println("before sort:" + holidays);Collections.sort(holidays); // Native sort for Date is chronologicalSystem.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 Masselements.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 ElementSystem.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;@Overridepublic 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());}}
}

参考：来自Tommy Alf的JCG合作伙伴 Tommy Alf的五种有用的Java排序方法 -博客博客。